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Although collagens are the most abundant proteins implicated in various disease pathways, essential mechanisms required for their proper folding and assembly are poorly understood. Heat‐shock protein 47 (HSP47), an ER‐resident chaperone, was mainly reported to fulfill key functions in folding and secretion of fibrillar collagens by stabilizing pro‐collagen triple‐helices. In this study, we demonstrate unique functions of HSP47 for different collagen subfamilies. Our results show that HSP47 binds to the N‐terminal region of procollagen I and is essential for its secretion. However, HSP47 ablation does not majorly impact collagen VI secretion, but its lateral assembly. Moreover, specific ablation of Hsp47 in murine keratinocytes revealed a new role for the transmembrane collagen XVII triple‐helix formation. Incompletely folded collagen XVII C‐termini protruding from isolated HSP47 null keratinocyte membrane vesicles could be fully restored upon the application of recombinant HSP47. Thus, our study expands the current view regarding the client repertoire and function of HSP47, as well as emphasizes its importance for transmembrane collagen folding.
Anna Köhler; Matthias Mörgelin; Jan M. Gebauer; Sinan Öcal; Thomas Imhof; Manuel Koch; Kazuhiro Nagata; Mats Paulsson; Monique Aumailley; Ulrich Baumann; Frank Zaucke; Gerhard Sengle. New specific HSP47 functions in collagen subfamily chaperoning. The FASEB Journal 2020, 34, 12040 -12052.
AMA StyleAnna Köhler, Matthias Mörgelin, Jan M. Gebauer, Sinan Öcal, Thomas Imhof, Manuel Koch, Kazuhiro Nagata, Mats Paulsson, Monique Aumailley, Ulrich Baumann, Frank Zaucke, Gerhard Sengle. New specific HSP47 functions in collagen subfamily chaperoning. The FASEB Journal. 2020; 34 (9):12040-12052.
Chicago/Turabian StyleAnna Köhler; Matthias Mörgelin; Jan M. Gebauer; Sinan Öcal; Thomas Imhof; Manuel Koch; Kazuhiro Nagata; Mats Paulsson; Monique Aumailley; Ulrich Baumann; Frank Zaucke; Gerhard Sengle. 2020. "New specific HSP47 functions in collagen subfamily chaperoning." The FASEB Journal 34, no. 9: 12040-12052.
Glutamine fructose-6-phosphate amidotransferase (GFAT) is the key enzyme in the hexosamine pathway (HP) that produces uridine 5′-diphospho-N-acetyl-d-glucosamine (UDP-GlcNAc), linking energy metabolism with posttranslational protein glycosylation. In Caenorhabditis elegans, we previously identified gfat-1 gain-of-function mutations that elevate UDP-GlcNAc levels, improve protein homeostasis, and extend lifespan. GFAT is highly conserved, but the gain-of-function mechanism and its relevance in mammalian cells remained unclear. Here, we present the full-length crystal structure of human GFAT-1 in complex with various ligands and with important mutations. UDP-GlcNAc directly interacts with GFAT-1, inhibiting catalytic activity. The longevity-associated G451E variant shows drastically reduced sensitivity to UDP-GlcNAc inhibition in enzyme activity assays. Our structural and functional data point to a critical role of the interdomain linker in UDP-GlcNAc inhibition. In mammalian cells, the G451E variant potently activates the HP. Therefore, GFAT-1 gain-of-function through loss of feedback inhibition constitutes a potential target for the treatment of age-related proteinopathies.
Sabine Ruegenberg; Moritz Horn; Christian Pichlo; Kira Allmeroth; Ulrich Baumann; Martin S. Denzel. Loss of GFAT-1 feedback regulation activates the hexosamine pathway that modulates protein homeostasis. Nature Communications 2020, 11, 687 -16.
AMA StyleSabine Ruegenberg, Moritz Horn, Christian Pichlo, Kira Allmeroth, Ulrich Baumann, Martin S. Denzel. Loss of GFAT-1 feedback regulation activates the hexosamine pathway that modulates protein homeostasis. Nature Communications. 2020; 11 (1):687-16.
Chicago/Turabian StyleSabine Ruegenberg; Moritz Horn; Christian Pichlo; Kira Allmeroth; Ulrich Baumann; Martin S. Denzel. 2020. "Loss of GFAT-1 feedback regulation activates the hexosamine pathway that modulates protein homeostasis." Nature Communications 11, no. 1: 687-16.
Collagen model peptides (CMPs) serve as tools for understanding stability and function of the collagen triple helix and have a potential for biomedical applications. In the past, interstrand cross‐linking or conformational preconditioning of proline units through stereoelectronic effects have been utilized in the design of stabilized CMPs. To further study the effects determining collagen triple helix stability we investigated a series of CMPs containing synthetic diproline‐mimicking modules (ProMs), which were preorganized in a PPII‐helix‐type conformation by a functionalizable intrastrand C2 bridge. Results of CD‐based denaturation studies were correlated with calculated (DFT) conformational preferences of the ProM units, revealing that the relative helix stability is mainly governed by an interplay of main‐chain preorganization, ring‐flip preference, adaptability, and steric effects. Triple helix integrity was proven by crystal structure analysis and binding to HSP47.
Andreas Maaßen; Jan Gebauer; Elena Theres Abraham; Isabelle Grimm; Jörg‐Martin Neudörfl; Ronald Kühne; Dr. Ines Neundorf; Dr. Ulrich Baumann; Dr. Hans‐Günther Schmalz. Triple‐Helix‐Stabilizing Effects in Collagen Model Peptides Containing PPII‐Helix‐Preorganized Diproline Modules. Angewandte Chemie International Edition 2020, 59, 5747 -5755.
AMA StyleAndreas Maaßen, Jan Gebauer, Elena Theres Abraham, Isabelle Grimm, Jörg‐Martin Neudörfl, Ronald Kühne, Dr. Ines Neundorf, Dr. Ulrich Baumann, Dr. Hans‐Günther Schmalz. Triple‐Helix‐Stabilizing Effects in Collagen Model Peptides Containing PPII‐Helix‐Preorganized Diproline Modules. Angewandte Chemie International Edition. 2020; 59 (14):5747-5755.
Chicago/Turabian StyleAndreas Maaßen; Jan Gebauer; Elena Theres Abraham; Isabelle Grimm; Jörg‐Martin Neudörfl; Ronald Kühne; Dr. Ines Neundorf; Dr. Ulrich Baumann; Dr. Hans‐Günther Schmalz. 2020. "Triple‐Helix‐Stabilizing Effects in Collagen Model Peptides Containing PPII‐Helix‐Preorganized Diproline Modules." Angewandte Chemie International Edition 59, no. 14: 5747-5755.
Collagen model peptides (CMPs) serve as tools for understanding stability and function of the collagen triple helix and have a potential for biomedical applications. In the past, interstrand cross‐linking or conformational preconditioning of proline units through stereoelectronic effects have been utilized in the design of stabilized CMPs. To further study the effects determining collagen triple helix stability we investigated a series of CMPs containing synthetic diproline‐mimicking modules (ProMs), which were preorganized in a PPII‐helix‐type conformation by a functionalizable intrastrand C2 bridge. Results of CD‐based denaturation studies were correlated with calculated (DFT) conformational preferences of the ProM units, revealing that the relative helix stability is mainly governed by an interplay of main‐chain preorganization, ring‐flip preference, adaptability, and steric effects. Triple helix integrity was proven by crystal structure analysis and binding to HSP47.
Andreas Maaßen; Jan M. Gebauer; Elena Theres Abraham; Isabelle Grimm; Jörg‐Martin Neudörfl; Ronald Kühne; Dr. Ines Neundorf; Dr. Ulrich Baumann; Dr. Hans‐Günther Schmalz. Triple‐Helix‐Stabilizing Effects in Collagen Model Peptides Containing PPII‐Helix‐Preorganized Diproline Modules. Angewandte Chemie 2020, 132, 5796 -5804.
AMA StyleAndreas Maaßen, Jan M. Gebauer, Elena Theres Abraham, Isabelle Grimm, Jörg‐Martin Neudörfl, Ronald Kühne, Dr. Ines Neundorf, Dr. Ulrich Baumann, Dr. Hans‐Günther Schmalz. Triple‐Helix‐Stabilizing Effects in Collagen Model Peptides Containing PPII‐Helix‐Preorganized Diproline Modules. Angewandte Chemie. 2020; 132 (14):5796-5804.
Chicago/Turabian StyleAndreas Maaßen; Jan M. Gebauer; Elena Theres Abraham; Isabelle Grimm; Jörg‐Martin Neudörfl; Ronald Kühne; Dr. Ines Neundorf; Dr. Ulrich Baumann; Dr. Hans‐Günther Schmalz. 2020. "Triple‐Helix‐Stabilizing Effects in Collagen Model Peptides Containing PPII‐Helix‐Preorganized Diproline Modules." Angewandte Chemie 132, no. 14: 5796-5804.
RTX proteins are a large family of polypeptides of mainly Gram-negative origin that are secreted into the extracellular medium by a type I secretion system featuring a non-cleavable C-terminal secretion signal, which is preceded by a variable number of nine-residue tandem repeats. The three-dimensional structure forms a parallel β-roll, where β-strands of two parallel sheets are connected by calcium-binding linkers in such a way that a right-handed spiral is built. The Ca2+ ions are an integral part of the structure, which cannot form without them. The structural determinants of this unique architecture will be reviewed with its conservations and variations together with the implication for secretion and folding of these proteins. The general purpose of the RTX domains appears to act as an internal chaperone that keeps the polypeptide unfolded in the calcium-deprived cytosol and triggers folding in the calcium-rich extracellular medium. A rather recent addition to the structural biology of the RTX toxin is a variant occurring in a large RTX adhesin, where this non-canonical β-roll binds to ice and diatoms.
Ulrich Baumann. Structure–Function Relationships of the Repeat Domains of RTX Toxins. Toxins 2019, 11, 657 .
AMA StyleUlrich Baumann. Structure–Function Relationships of the Repeat Domains of RTX Toxins. Toxins. 2019; 11 (11):657.
Chicago/Turabian StyleUlrich Baumann. 2019. "Structure–Function Relationships of the Repeat Domains of RTX Toxins." Toxins 11, no. 11: 657.
Pro-Pro endopeptidase-1 (PPEP-1) is a secreted metalloprotease from the bacterial pathogen Clostridium difficile that cleaves two endogenous adhesion proteins. PPEP-1 is therefore important for bacterial motility and hence for efficient gut colonization during infection. PPEP-1 exhibits a unique specificity for Pro-Pro peptide bonds within the consensus sequence VNP↓PVP. In this study, we combined information from crystal and NMR structures with mutagenesis and enzyme kinetics to investigate the mechanism and substrate specificity of PPEP-1. Our analyses revealed that the substrate-binding cleft of PPEP-1 is shaped complementarily to the major conformation of the substrate in solution. We found that it possesses features that accept a tertiary amide and help discriminate P1′ residues by their amide hydrogen bond-donating potential. We also noted that residues Lys-101, Trp-103, and Glu-184 are crucial for proteolytic activity. Upon substrate binding, these residues position a flexible loop over the substrate-binding cleft and modulate the second coordination sphere of the catalytic zinc ion. On the basis of these findings, we propose an induced-fit model in which prestructured substrates are recognized followed by substrate positioning within the active-site cleft and a concomitant increase in the Lewis acidity of the catalytic Zn2+ ion. In conclusion, our findings provide detailed structural and mechanistic insights into the substrate recognition and specificity of PPEP-1 from the common gut pathogen C. difficile.
Christian Pichlo; Linda Juetten; Fabian Wojtalla; Magdalena Schacherl; Dolores Diaz; Ulrich Baumann. Molecular determinants of the mechanism and substrate specificity of Clostridium difficile proline-proline endopeptidase-1. Journal of Biological Chemistry 2019, 294, 11525 -11535.
AMA StyleChristian Pichlo, Linda Juetten, Fabian Wojtalla, Magdalena Schacherl, Dolores Diaz, Ulrich Baumann. Molecular determinants of the mechanism and substrate specificity of Clostridium difficile proline-proline endopeptidase-1. Journal of Biological Chemistry. 2019; 294 (30):11525-11535.
Chicago/Turabian StyleChristian Pichlo; Linda Juetten; Fabian Wojtalla; Magdalena Schacherl; Dolores Diaz; Ulrich Baumann. 2019. "Molecular determinants of the mechanism and substrate specificity of Clostridium difficile proline-proline endopeptidase-1." Journal of Biological Chemistry 294, no. 30: 11525-11535.
In this study, we report on the modification of a 3,4-diaryl-isoxazole-based CK1 inhibitor with chiral pyrrolidine scaffolds to develop potent and selective CK1 inhibitors. The pharmacophore of the lead structure was extended towards the ribose pocket of the adenosine triphosphate (ATP) binding site driven by structure-based drug design. For an upscale compatible multigram synthesis of the functionalized pyrrolidine scaffolds, we used a chiral pool synthetic route starting from methionine. Biological evaluation of key compounds in kinase and cellular assays revealed significant effects of the scaffolds towards activity and selectivity, however, the absolute configuration of the chiral moieties only exhibited a limited effect on inhibitory activity. X-ray crystallographic analysis of ligand-CK1δ complexes confirmed the expected binding mode of the 3,4-diaryl-isoxazole inhibitors. Surprisingly, the original compounds underwent spontaneous Pictet-Spengler cyclization with traces of formaldehyde during the co-crystallization process to form highly potent new ligands. Our data suggests chiral “ribose-like” pyrrolidine scaffolds have interesting potential for modifications of pharmacologically active compounds.
Andreas Luxenburger; Dorian Schmidt; Chiara Ianes; Christian Pichlo; Marc Krüger; Thorsten Von Drathen; Elena Brunstein; Graeme J. Gainsford; Ulrich Baumann; Uwe Knippschild; Christian Peifer. Design, Synthesis and Biological Evaluation of Isoxazole-Based CK1 Inhibitors Modified with Chiral Pyrrolidine Scaffolds. Molecules 2019, 24, 873 .
AMA StyleAndreas Luxenburger, Dorian Schmidt, Chiara Ianes, Christian Pichlo, Marc Krüger, Thorsten Von Drathen, Elena Brunstein, Graeme J. Gainsford, Ulrich Baumann, Uwe Knippschild, Christian Peifer. Design, Synthesis and Biological Evaluation of Isoxazole-Based CK1 Inhibitors Modified with Chiral Pyrrolidine Scaffolds. Molecules. 2019; 24 (5):873.
Chicago/Turabian StyleAndreas Luxenburger; Dorian Schmidt; Chiara Ianes; Christian Pichlo; Marc Krüger; Thorsten Von Drathen; Elena Brunstein; Graeme J. Gainsford; Ulrich Baumann; Uwe Knippschild; Christian Peifer. 2019. "Design, Synthesis and Biological Evaluation of Isoxazole-Based CK1 Inhibitors Modified with Chiral Pyrrolidine Scaffolds." Molecules 24, no. 5: 873.
COMP (cartilage oligomeric matrix protein) is a member of the thrombospondin family and forms homopentamers as well as mixed heterooligomers with its closely related family member TSP-4. COMP is long known to bind to collagens and to influence collagen fibril formation. Recent work indicates that already intracellular interaction with collagen is important for collagen secretion. However, the exact binding site of COMP on the collagen triple helix has not been described up to now. In this study we have identified a GXKGHR motif on the collagen II helix to bind to COMP, using a recombinantly expressed collagen II peptide library. This binding sequence is conserved throughout evolution and we demonstrate that TSP-4 binds to the same sequence. The identified binding motif overlaps with the recognition sites of many other collagen-binding partners (e.g. PEDF, Heparin) and also spans the lysine residues, which form collagen cross-links. COMP might thereby protect collagen helices from premature modification and cross-linking. Interestingly, this motif is only found in classical fibrillar collagens, although COMP is known to also bind other types. This might indicate that COMP has a unique interface for fibrillar collagens, thus making it an interesting target for the development of antifibrotic drugs.
Jan M. Gebauer; Anna Köhler; Helen Dietmar; Monika Gompert; Ines Neundorf; Frank Zaucke; Manuel Koch; Ulrich Baumann. COMP and TSP-4 interact specifically with the novel GXKGHR motif only found in fibrillar collagens. Scientific Reports 2018, 8, 17187 .
AMA StyleJan M. Gebauer, Anna Köhler, Helen Dietmar, Monika Gompert, Ines Neundorf, Frank Zaucke, Manuel Koch, Ulrich Baumann. COMP and TSP-4 interact specifically with the novel GXKGHR motif only found in fibrillar collagens. Scientific Reports. 2018; 8 (1):17187.
Chicago/Turabian StyleJan M. Gebauer; Anna Köhler; Helen Dietmar; Monika Gompert; Ines Neundorf; Frank Zaucke; Manuel Koch; Ulrich Baumann. 2018. "COMP and TSP-4 interact specifically with the novel GXKGHR motif only found in fibrillar collagens." Scientific Reports 8, no. 1: 17187.
Tetranuclear complexes [M4(LR)4] with M = Ni(II) or Zn(II), with a [2 × 2] grid-type structure, were assembled in good yields and purity from the easily accessible but unprecedented pyrazine-bridged bis(thiosemicarbazone) protoligands (ligand precursors) H2LR (1,4-pyrazine-2,5-bis(R-carbaldehyde-thiosemicarbazone); R = Me, Et, iPr, or Ph). The complexes were characterised in solution by NMR, MS, IR, and UV-Vis absorption spectroscopy and (spectro)electrochemical methods. HR-MS spectra unequivocally reveal that the tetranuclear species are very stable in solution and any measurements represent these species. Only at higher temperatures (fragmentation in solution: MS and in the solid: TG-DTA) or upon the addition of protons (acidic UV-Vis titrations) can the tetrameric entities be decomposed. Single crystal XRD measurement remained preliminary. Rapid loss of co-crystallised solvent molecules within the [2 × 2] grid-type structures resulted in crystals of very poor quality, but the results were qualitatively in line with spectroscopy, electrochemistry, and quantum chemical (DFT) calculations. IR and NMR spectroscopy point clearly to a thiolate coordination of dianionic (deprotonated) ligands. The electrochemistry reveals four electronically coupled and reversible one-electron reductions centred largely at the pyrazine bridges. EPR and UV-Vis spectroelectrochemical measurements in combination with DFT calculation support the assignment.
Natalia Arefyeva; Aaron Sandleben; Alexander Krest; Ulrich Baumann; Mathias Schäfer; Maxim Kempf; Axel Klein. [2 × 2] Molecular Grids of Ni(II) and Zn(II) with Redox-Active 1,4-Pyrazine-Bis(thiosemicarbazone) Ligands. Inorganics 2018, 6, 51 .
AMA StyleNatalia Arefyeva, Aaron Sandleben, Alexander Krest, Ulrich Baumann, Mathias Schäfer, Maxim Kempf, Axel Klein. [2 × 2] Molecular Grids of Ni(II) and Zn(II) with Redox-Active 1,4-Pyrazine-Bis(thiosemicarbazone) Ligands. Inorganics. 2018; 6 (2):51.
Chicago/Turabian StyleNatalia Arefyeva; Aaron Sandleben; Alexander Krest; Ulrich Baumann; Mathias Schäfer; Maxim Kempf; Axel Klein. 2018. "[2 × 2] Molecular Grids of Ni(II) and Zn(II) with Redox-Active 1,4-Pyrazine-Bis(thiosemicarbazone) Ligands." Inorganics 6, no. 2: 51.
The identification of initial lead conditions for successful protein crystallization is crucial for structural studies using X-ray crystallography. In order to reduce the number of false-negative conditions, an emerging number of fluorescence-based methods have been developed which allow more efficient identification of protein crystals and help to distinguish them from salt crystals. Detection of the native tryptophan fluorescence of protein crystals is one of the most widely used methods. However, this method can fail owing to the properties of the crystallized protein or the chemical composition of the crystallization trials. Here, a simple, fast and cost-efficient method employing 2,2,2-trichloroethanol (TCE) has been developed. It can be performed with a standard UV-light microscope and can be applied to cases in which detection of native tryptophan fluorescence fails. In four test cases this method had no effect on the diffraction properties of the crystals and no structural changes were observed. Further evidence is provided that TCE can be added to crystallization trials during their preparation, making this method compatible with high-throughput approaches.
Christian Pichlo; Christine Toelzer; Konrad Chojnacki; Sinan Öcal; Matthias Uthoff; Sabine Ruegenberg; Thomas Hermanns; Magdalena Schacherl; Martin S. Denzel; Kay Hofmann; Karsten Niefind; Ulrich Baumann. Improved protein-crystal identification by using 2,2,2-trichloroethanol as a fluorescence enhancer. Acta Crystallographica Section F Structural Biology Communications 2018, 74, 307 -314.
AMA StyleChristian Pichlo, Christine Toelzer, Konrad Chojnacki, Sinan Öcal, Matthias Uthoff, Sabine Ruegenberg, Thomas Hermanns, Magdalena Schacherl, Martin S. Denzel, Kay Hofmann, Karsten Niefind, Ulrich Baumann. Improved protein-crystal identification by using 2,2,2-trichloroethanol as a fluorescence enhancer. Acta Crystallographica Section F Structural Biology Communications. 2018; 74 (5):307-314.
Chicago/Turabian StyleChristian Pichlo; Christine Toelzer; Konrad Chojnacki; Sinan Öcal; Matthias Uthoff; Sabine Ruegenberg; Thomas Hermanns; Magdalena Schacherl; Martin S. Denzel; Kay Hofmann; Karsten Niefind; Ulrich Baumann. 2018. "Improved protein-crystal identification by using 2,2,2-trichloroethanol as a fluorescence enhancer." Acta Crystallographica Section F Structural Biology Communications 74, no. 5: 307-314.
Inherited point mutations in collagen II in humans affecting mainly cartilage are broadly classified as chondrodysplasias. Most mutations occur in the glycine (Gly) of the Gly-X-Y repeats leading to destabilization of the triple helix. Arginine to cysteine substitutions that occur at either the X or Y position within the Gly-X-Y cause different phenotypes like Stickler syndrome and congenital spondyloepiphyseal dysplasia (SEDC). We investigated the consequences of arginine to cysteine substitutions (X or Y position within the Gly-X-Y) towards the N and C terminus of the triple helix. Protein expression and its secretion trafficking were analyzed. Substitutions R75C, R134C and R704C did not alter the thermal stability with respect to wild type; R740C and R789C proteins displayed significantly reduced melting temperatures (Tm) affecting thermal stability. Additionally, R740C and R789C were susceptible to proteases; in cell culture, R789C protein was further cleaved by matrix metalloproteinases (MMPs) resulting in expression of only a truncated fragment affecting its secretion and intracellular retention. Retention of misfolded R740C and R789C proteins triggered an ER stress response leading to apoptosis of the expressing cells. Arginine to cysteine mutations towards the C-terminus of the triple helix had a deleterious effect, whereas mutations towards the N-terminus of the triple helix (R75C and R134C) and R704C had less impact.
Salin A. Chakkalakal; Juliane Heilig; Ulrich Baumann; Mats Paulsson; Frank Zaucke. Impact of Arginine to Cysteine Mutations in Collagen II on Protein Secretion and Cell Survival. International Journal of Molecular Sciences 2018, 19, 541 .
AMA StyleSalin A. Chakkalakal, Juliane Heilig, Ulrich Baumann, Mats Paulsson, Frank Zaucke. Impact of Arginine to Cysteine Mutations in Collagen II on Protein Secretion and Cell Survival. International Journal of Molecular Sciences. 2018; 19 (2):541.
Chicago/Turabian StyleSalin A. Chakkalakal; Juliane Heilig; Ulrich Baumann; Mats Paulsson; Frank Zaucke. 2018. "Impact of Arginine to Cysteine Mutations in Collagen II on Protein Secretion and Cell Survival." International Journal of Molecular Sciences 19, no. 2: 541.
The involvement of protein kinase CK1δ in the pathogenesis of severe disorders such as Alzheimer’s disease, amyotrophic lateral sclerosis, familial advanced sleep phase syndrome, and cancer has dramatically increased interest in the development of effective small molecule inhibitors for both therapeutic application and basic research. Unfortunately, the design of CK1 isoform-specific compounds has proved to be highly complicated due to the existence of six evolutionarily conserved human CK1 members that possess similar, different, or even opposite physiological and pathophysiological implications. Consequently, only few potent and selective CK1δ inhibitors have been reported so far and structurally divergent approaches are urgently needed in order to establish SAR that might enable complete discrimination of CK1 isoforms and related p38α MAPK. In this study we report on design and characterization of optimized 4,5-diarylimidazoles as highly effective ATP-competitive inhibitors of CK1δ with compounds 11b (IC50 CK1δ = 4 nM, IC50 CK1ε = 25 nM), 12a (IC50 CK1δ = 19 nM, IC50 CK1ε = 227 nM), and 16b (IC50 CK1δ = 8 nM, IC50 CK1ε = 81 nM) being among the most potent CK1δ-targeting agents published to date. Inhibitor compound 11b, displaying potential as a pharmacological tool, has further been profiled over a panel of 321 protein kinases exhibiting high selectivity. Cellular efficacy has been evaluated in human pancreatic cancer cell lines Colo357 (EC50 = 3.5 µM) and Panc89 (EC50 = 1.5 µM). SAR is substantiated by X-ray crystallographic analysis of 16b in CK1δ and 11b in p38α.
Jakob Halekotte; Lydia Witt; Chiara Ianes; Marc Krüger; Mike Bührmann; Daniel Rauh; Christian Pichlo; Elena Brunstein; Andreas Luxenburger; Ulrich Baumann; Uwe Knippschild; Joachim Bischof; Christian Peifer. Optimized 4,5-Diarylimidazoles as Potent/Selective Inhibitors of Protein Kinase CK1δ and Their Structural Relation to p38α MAPK. Molecules 2017, 22, 522 .
AMA StyleJakob Halekotte, Lydia Witt, Chiara Ianes, Marc Krüger, Mike Bührmann, Daniel Rauh, Christian Pichlo, Elena Brunstein, Andreas Luxenburger, Ulrich Baumann, Uwe Knippschild, Joachim Bischof, Christian Peifer. Optimized 4,5-Diarylimidazoles as Potent/Selective Inhibitors of Protein Kinase CK1δ and Their Structural Relation to p38α MAPK. Molecules. 2017; 22 (4):522.
Chicago/Turabian StyleJakob Halekotte; Lydia Witt; Chiara Ianes; Marc Krüger; Mike Bührmann; Daniel Rauh; Christian Pichlo; Elena Brunstein; Andreas Luxenburger; Ulrich Baumann; Uwe Knippschild; Joachim Bischof; Christian Peifer. 2017. "Optimized 4,5-Diarylimidazoles as Potent/Selective Inhibitors of Protein Kinase CK1δ and Their Structural Relation to p38α MAPK." Molecules 22, no. 4: 522.
Heat shock protein 47 is an ER (endoplasmic reticulum) resident collagen-specific chaperone and essential for proper formation of the characteristic collagen triple helix. It preferentially binds to the folded conformation of its clients and accompanies them from the ER to the Golgi compartment where it releases them and is recycled back to the ER. Unlike other chaperones, the binding and release cycles are not governed by nucleotide exchange and hydrolysis, but presumably the dissociation of the HSP47-procollagen complex is triggered by the lower pH in the Golgi (6.3) compared to the ER (7.4). Histidine residues have been suggested as triggers owing to their approximate textbook pKa value of 6.1 for their side-chains. We present here an extensive theoretical and experimental study of the 14 histidine residues present in canine HSP47, where we have mutated all histidine residues in the collagen binding interface and additionally all those which were predicted to undergo a significant change in protonation state between pH 7 and 6. These mutants were characterized by biolayer interferometry for their pH‑dependent binding to a collagen model. One mutant (H238N) loses binding, which can be explained by a rearrangement of the Arg222 and Asp385 residues, which are crucial for specific collagen recognition. Most of the other mutants were remarkably silent, but a double mutant with His273 and His274 exchanged for asparagines exhibits a much less pronounced pH-dependency of collagen binding. This effect is mainly caused by a lower kOFF at the low pH values.
Sinan Oecal; Eileen Socher; Matthias Uthoff; Corvin Ernst; Frank Zaucke; Heinrich Sticht; Ulrich Baumann; Jan M. Gebauer. The pH-dependent Client Release from the Collagen-specific Chaperone HSP47 Is Triggered by a Tandem Histidine Pair. Journal of Biological Chemistry 2016, 291, 12612 -12626.
AMA StyleSinan Oecal, Eileen Socher, Matthias Uthoff, Corvin Ernst, Frank Zaucke, Heinrich Sticht, Ulrich Baumann, Jan M. Gebauer. The pH-dependent Client Release from the Collagen-specific Chaperone HSP47 Is Triggered by a Tandem Histidine Pair. Journal of Biological Chemistry. 2016; 291 (24):12612-12626.
Chicago/Turabian StyleSinan Oecal; Eileen Socher; Matthias Uthoff; Corvin Ernst; Frank Zaucke; Heinrich Sticht; Ulrich Baumann; Jan M. Gebauer. 2016. "The pH-dependent Client Release from the Collagen-specific Chaperone HSP47 Is Triggered by a Tandem Histidine Pair." Journal of Biological Chemistry 291, no. 24: 12612-12626.
Pathogenic bacteria secrete proteases to evade host defense and to acquire nutrients. In this issue of Structure, Arolas et al. (2016) describe the structural basis of activation and latency of InhA, a major secreted protease of Bacillus anthracis.
Magdalena Schacherl; Ulrich Baumann. Feeding Anthrax: The Crystal Structure of Bacillus anthracis InhA Protease. Structure 2016, 24, 1 -2.
AMA StyleMagdalena Schacherl, Ulrich Baumann. Feeding Anthrax: The Crystal Structure of Bacillus anthracis InhA Protease. Structure. 2016; 24 (1):1-2.
Chicago/Turabian StyleMagdalena Schacherl; Ulrich Baumann. 2016. "Feeding Anthrax: The Crystal Structure of Bacillus anthracis InhA Protease." Structure 24, no. 1: 1-2.
The U32 family is a collection of over 2500 annotated peptidases in the MEROPS database with unknown catalytic mechanism. They mainly occur in bacteria and archaea, but a few representatives have also been identified in eukarya. Many of the U32 members have been linked to pathogenicity, such as proteins from Helicobacter and Salmonella. The first crystal structure analysis of a U32 catalytic domain from Methanopyrus kandleri (gene mk0906) reveals a modified ()8 TIM-barrel fold with some unique features. The connecting segment between strands 7 and 8 is extended and helix 7 is located on top of the C-terminal end of the barrel body. The protein exhibits a dimeric quaternary structure in which a zinc ion is symmetrically bound by histidine and cysteine side chains from both monomers. These residues reside in conserved sequence motifs. No typical proteolytic motifs are discernible in the three-dimensional structure, and biochemical assays failed to demonstrate proteolytic activity. A tunnel in which an acetate ion is bound is located in the C-terminal part of the -barrel. Two hydrophobic grooves lead to a tunnel at the C-terminal end of the barrel in which an acetate ion is bound. One of the grooves binds to a Strep-Tag II of another dimer in the crystal lattice. Thus, these grooves may be binding sites for hydrophobic peptides or other ligands.
Magdalena Schacherl; Angelika A. M. Montada; Elena Brunstein; Ulrich Baumann. The first crystal structure of the peptidase domain of the U32 peptidase family. Acta Crystallographica Section D Biological Crystallography 2015, 71, 2505 -2512.
AMA StyleMagdalena Schacherl, Angelika A. M. Montada, Elena Brunstein, Ulrich Baumann. The first crystal structure of the peptidase domain of the U32 peptidase family. Acta Crystallographica Section D Biological Crystallography. 2015; 71 (12):2505-2512.
Chicago/Turabian StyleMagdalena Schacherl; Angelika A. M. Montada; Elena Brunstein; Ulrich Baumann. 2015. "The first crystal structure of the peptidase domain of the U32 peptidase family." Acta Crystallographica Section D Biological Crystallography 71, no. 12: 2505-2512.
Summary Clostridium difficile is a pathogenic bacterium causing gastrointestinal diseases from mild diarrhea to toxic megacolon. In common with other pathogenic bacteria, C. difficile secretes proteins involved in adhesion, colonization, and dissemination. The recently identified Zmp1 is an extracellular metalloprotease showing a unique specificity for Pro-Pro peptide bonds. The endogenous substrates of Zmp1 are two surface proteins implicated in adhesion of C. difficile to surface proteins of human cells. Thus, Zmp1 is believed to be involved in the regulation of the adhesion-motility balance of C. difficile. Here, we report crystal structures of Zmp1 from C. difficile in its unbound and peptide-bound forms. The structure analysis revealed a fold similar to Bacillus anthracis lethal factor. Crystal structures in the open and closed conformation of the S-loop shed light on the mode of binding of the substrate, and reveal important residues for substrate recognition and the strict specificity of Zmp1 for Pro-Pro peptide bonds.
Magdalena Schacherl; Christian Pichlo; Ines Neundorf; Ulrich Baumann. Structural Basis of Proline-Proline Peptide Bond Specificity of the Metalloprotease Zmp1 Implicated in Motility of Clostridium difficile. Structure 2015, 23, 1632 -1642.
AMA StyleMagdalena Schacherl, Christian Pichlo, Ines Neundorf, Ulrich Baumann. Structural Basis of Proline-Proline Peptide Bond Specificity of the Metalloprotease Zmp1 Implicated in Motility of Clostridium difficile. Structure. 2015; 23 (9):1632-1642.
Chicago/Turabian StyleMagdalena Schacherl; Christian Pichlo; Ines Neundorf; Ulrich Baumann. 2015. "Structural Basis of Proline-Proline Peptide Bond Specificity of the Metalloprotease Zmp1 Implicated in Motility of Clostridium difficile." Structure 23, no. 9: 1632-1642.
The crystal structure of a truncated, soluble quadruple mutant of FtsH from Aquifex aeolicus comprising the AAA and protease domains has been determined at 2.96 Å resolution in space group I222. The protein crystallizes as a hexamer, with the protease domain forming layers in the ab plane. Contacts between these layers are mediated by the AAA domains. These are highly disordered in one crystal form, but are clearly visible in a related form with a shorter c axis. Here, adenosine diphosphate (ADP) is bound to each subunit and the AAA ring exhibits twofold symmetry. The arrangement is different from the ADP-bound state of an analogously truncated, soluble FtsH construct from Thermotoga maritima. The pore is completely closed and the phenylalanine residues in the pore line a contiguous path. The protease hexamer is very similar to those described for other FtsH structures. To resolve certain open issues regarding a conserved glycine in the linker between the AAA and protease domains, as well as the active-site switch β-strand, mutations have been introduced in the full-length membrane-bound protein. Activity analysis of these point mutants reveals the crucial importance of these residues for proteolytic activity and is in accord with previous interpretation of the active-site switch and the importance of the linker glycine residue.
Marina Vostrukhina; Alexander Popov; Elena Brunstein; Martin A. Lanz; Renato Baumgartner; Christoph Bieniossek; Magdalena Schacherl; Ulrich Baumann. The structure of Aquifex aeolicus FtsH in the ADP-bound state reveals a C 2-symmetric hexamer. Acta Crystallographica Section D Biological Crystallography 2015, 71, 1307 -1318.
AMA StyleMarina Vostrukhina, Alexander Popov, Elena Brunstein, Martin A. Lanz, Renato Baumgartner, Christoph Bieniossek, Magdalena Schacherl, Ulrich Baumann. The structure of Aquifex aeolicus FtsH in the ADP-bound state reveals a C 2-symmetric hexamer. Acta Crystallographica Section D Biological Crystallography. 2015; 71 (6):1307-1318.
Chicago/Turabian StyleMarina Vostrukhina; Alexander Popov; Elena Brunstein; Martin A. Lanz; Renato Baumgartner; Christoph Bieniossek; Magdalena Schacherl; Ulrich Baumann. 2015. "The structure of Aquifex aeolicus FtsH in the ADP-bound state reveals a C 2-symmetric hexamer." Acta Crystallographica Section D Biological Crystallography 71, no. 6: 1307-1318.
Murein recycling is a process in which microorganisms recover peptidoglycan-degradation products in order to utilize them in cell wall biosynthesis or basic metabolic pathways. Methanogens such asMethanopyrus kandlericontain pseudomurein, which differs from bacterial murein in its composition and branching. Here, four crystal structures of the putative sugar kinase MK0840 fromM. kandleriin apo and nucleotide-bound states are reported. MK0840 shows high similarity to bacterial anhydro-N-acetylmuramic acid kinase, which is involved in murein recycling. The structure shares a common fold with panthothenate kinase and the 2-hydroxyglutaryl-CoA dehydratase component A, both of which are members of the ASKHA (acetate and sugar kinases/Hsc70/actin) superfamily of phosphotransferases. Local conformational changes in the nucleotide-binding site between the apo and holo forms are observed upon nucleotide binding. Further insight is given into domain movements and putative active-site residues are identified.
Magdalena Schacherl; Sandro Waltersperger; Ulrich Baumann. Structural characterization of the ribonuclease H-like type ASKHA superfamily kinase MK0840 fromMethanopyrus kandleri. Acta Crystallographica Section D Biological Crystallography 2013, 69, 2440 -2450.
AMA StyleMagdalena Schacherl, Sandro Waltersperger, Ulrich Baumann. Structural characterization of the ribonuclease H-like type ASKHA superfamily kinase MK0840 fromMethanopyrus kandleri. Acta Crystallographica Section D Biological Crystallography. 2013; 69 (12):2440-2450.
Chicago/Turabian StyleMagdalena Schacherl; Sandro Waltersperger; Ulrich Baumann. 2013. "Structural characterization of the ribonuclease H-like type ASKHA superfamily kinase MK0840 fromMethanopyrus kandleri." Acta Crystallographica Section D Biological Crystallography 69, no. 12: 2440-2450.
Capítulo en: Rawlings, Neil D.; Salvesen, Guy (eds.). Handbook of Proteolytic Enzymes. 3rd ed. London: Academic Press, 2013, vol. 1, chapter 270, p.1208-1211. ISBN 978-0-12-382219-2. ISBN (V1) 978-0-12-407744-7Peer Reviewe
Ulrich Baumann; F. Xavier Gomis-Rüth. Ulilysin (Methanosarcina acetivorans). Handbook of Proteolytic Enzymes 2012, 1208 -1211.
AMA StyleUlrich Baumann, F. Xavier Gomis-Rüth. Ulilysin (Methanosarcina acetivorans). Handbook of Proteolytic Enzymes. 2012; ():1208-1211.
Chicago/Turabian StyleUlrich Baumann; F. Xavier Gomis-Rüth. 2012. "Ulilysin (Methanosarcina acetivorans)." Handbook of Proteolytic Enzymes , no. : 1208-1211.
Milton T. Stubbs; Ulrich Baumann. No end in sight: the development of protein crystallography in Martinsried. Biological Chemistry 2012, 393, 1025 -1026.
AMA StyleMilton T. Stubbs, Ulrich Baumann. No end in sight: the development of protein crystallography in Martinsried. Biological Chemistry. 2012; 393 (10):1025-1026.
Chicago/Turabian StyleMilton T. Stubbs; Ulrich Baumann. 2012. "No end in sight: the development of protein crystallography in Martinsried." Biological Chemistry 393, no. 10: 1025-1026.