Summary: Most extremophilic anaerobes possess a sulfur formation (Suf) system for Fe–S cluster biogenesis. In addition to its essential role in redox chemistry and stress responses of Fe–S cluster proteins, the Suf system may play an important role in keratin degradation by Fervidobacterium islandicum AW‐1. Comparative genomics of the order Thermotogales revealed that the feather‐degrading F. islandicum AW‐1 has a complete Suf‐like machinery (SufCBDSU) that is highly expressed in cells grown on native feathers in the absence of elemental sulfur (S ⁰ ). On the other hand, F. islandicum AW‐1 exhibited a significant retardation in the Suf system‐mediated keratin degradation in the presence of S ⁰ . Detailed differential expression analysis of sulfur assimilation machineries unveiled the mechanism by which an efficient sulfur delivery from persulfurated SufS to SufU is achieved during keratinolysis under sulfur starvation. Indeed, addition of SufS–SufU to cell extracts containing keratinolytic proteases accelerated keratin decomposition in vitro under reducing conditions. Remarkably, mass spectrometric analysis of extracellular and intracellular levels of amino acids suggested that redox homeostasis within cells coupled to extracellular cysteine and cystine recycling might be a prerequisite for keratinolysis. Taken together, these results suggest that the Suf‐like machinery including the SufS–SufU complex may contribute to sulfur availability for an extracellular reducing environment as well as intracellular redox homeostasis through cysteine released from keratin hydrolysate under starvation conditions.

Small cell lung cancer (SCLC) is a devastating disease, and current therapies have not greatly improved the 5-year survival rates. Topoisomerase (Top) inhibition is a treatment modality for SCLC; however, the response is short lived. Consequently, our research has focused on improving SCLC therapeutics through the identification of novel targets. Previously, we identified MNNG HOS transforming gene (MET) to be overexpressed and functional in SCLC. Herein, we investigated the therapeutic potential of combinatorial targeting of MET using SU11274 and Top1 using 7-ethyl-10-hydroxycamptothecin (SN-38). MET and TOP1 gene copy numbers and protein expression were determined in 29 patients with limited (n = 11) and extensive (n = 18) disease. MET gene copy number was significantly increased (>6 copies) in extensive disease compared with limited disease (P = 0.015). Similar TOP1 gene copy numbers were detected in limited and extensive disease. Immunohistochemical staining revealed a significantly higher Top1 nuclear expression in extensive (0.93) versus limited (0.15) disease (P = 0.04). Interestingly, a significant positive correlation was detected between MET gene copy number and Top1 nuclear expression (r = 0.5). In vitro stimulation of H82 cells revealed hepatocyte growth factor (HGF)–induced nuclear colocalization of p-MET and Top1. Furthermore, activation of the HGF/MET axis enhanced Top1 activity, which was abrogated by SU11274. Combination of SN-38 with SU11274 dramatically decreased SCLC growth as compared with either drug alone. Collectively, these findings suggest that the combinatorial inhibition of MET and Top1 is a potentially efficacious treatment strategy for SCLC. Mol Cancer Ther; 13(3); 576–84. ©2013 AACR.

Every year, the poultry business worldwide produces at least 8.5 billion tonnes of chicken feathers, making it one of the major landfill pollutants in the world. Biodegradation and recycling of native feathers is difficult due to the presence of numerous disulfide linkages in the feather’s major constituent, keratin. Denaturation of such recalcitrant protein is thermodynamically favored at high temperatures. Therefore, the lookout for the enzymes that degrade keratin (keratinases) from thermophilic bacteria resulted in the identification of thermostable enzymes favoring feather degradation at high temperatures. This review presents a comprehensive analysis of the biochemical properties and structural attributes of thermostable keratinases, emphasizing their catalytic mechanisms, stability at high temperatures, and substrate specificity. Our exploration of structural features enables us to understand the molecular architecture of these enzymes for protein engineering that might enhance the keratinolytic activity and thermostability further. As the field of protein engineering advances, there exists a pressing requirement for integration of structural data with pragmatic engineering applications. Our review addresses for the first time the detailed structural aspects of thermostable bacterial keratinolytic enzymes that will facilitate the development of modified keratinases through protein engineering for a broad range of industrial applications, such as in the production of biofuels, leather processing, and waste management. Keypoints: • Efficient eco-friendly bioremediation of feather landfill pollutant using thermophilic keratinases. • Detailed structural and biochemical aspects of different thermophilic bacterial keratinases. • Combinations of thermostable keratinases for the enhanced feather degradation process Graphical Feather waste degradation using bacterial keratinases: an eco-friendly bioprocess for degradation of keratin-rich feather wastes into nutrient-rich byproducts, biofertilizers, and animal feed, using bacterial keratinases. A recycling strategy, contributing to pollutant degradation and waste management.

The enzyme known as SortaseA(SrtA) is widespread present in gram-positive bacteria. SrtA is responsible for anchoring a large number of surface protein virulence factors to the cell wall. This enzyme is not involved in bacterial growth and is also present on the cell membrane, which makes it more accessible for the design of inhibitors. In the case of Enterococcus faecalis (Ef), which is responsible for a wide range of nosocomial infections, SrtA from this organism promotes development of biofilm, which in turn makes bacteria resistant to antibiotics. Numerous inhibitors have been identified and characterized against Ef-SrtA; however, none have been clinically approved till now. Natural compounds and their derivatives showed inhibition against Ef-SrtA. In this work, a flavanoids-based in-house natural library was screened against Ef-SrtA to see how these molecules bind to active site of Ef-SrtA. Furthermore, the absorption, distribution, metabolism and excretion (ADME) properties of the top five compounds, Abyssinones lii, Apigenin, Rutin, Fisetin and Kaemferol, were calculated, Additionally, the correlation between the structure and function of these top five compounds was analyzed using Density Functional Theory (DFT) studies.

Tuberculosis, caused by Mycobacterium tuberculosis ranks second globally in terms of infectious disease-related deaths, after HIV. The resistance of M. tuberculosis to existing beta-lactam antibiotics is primarily due to chromosomally encoded gene blaC, which can hydrolyse predominantly available beta-lactam antibiotics. Despite the available beta-lactamase inhibitors with beta-lactam ring such as clavulanate, being efficacious, they lead the bacteria to develop an inhibitor escape mechanism. In contrast, the natural product inhibitors without beta-lactam ring that might resist bacterial escape mechanisms have the additional advantage of fewer side effects, higher bioavailability, and better bioremediation towards environmental sustainability. This study identifies novel natural inhibitors against BlaC, from the Natural Products Atlas database of PubChem and ZINC comprising 10,000 compounds using molecular docking and Molecular Dynamics (MD) simulations. The virtual screening and docking experiments demonstrated that the top 10 compounds exhibited favourable docking scores in the range of -7.59 to -9.63 kcal/mol compared to the reference molecule, Doripenem (-7.35 kcal/mol). Following targeted docking and ADMET analysis, three lead compounds Lecanorafuran A, Tryptoquivaline K, and Deacetylisowortmin A were selected for MD simulations for a period of 100 ns to evaluate the stability of the protein-ligand complexes. Based on Root Mean Square Deviation, Root Mean Square Fluctuation, Radius of gyration and Solvent Accessible Surface Area, PCA, and FEL analysis, it was found that Tryptoquivaline K exhibited consistent stability throughout the simulation. Additionally, Molecular Mechanics/Poisson-Boltzmann Surface Area (MMPBSA) analysis was conducted to assess the binding affinity of the complex. All these analyses validate that the natural compound Tryptoquivaline K exhibits potential as a promising BlaC inhibitor but warrants further validation through experimental studies in this aspect.