NKCC and KCC transporters mediate coupled transport of Na⁺+K⁺+Cl⁻ and K⁺+Cl⁻ across the plasma membrane, thus regulating cell Cl⁻ concentration and cell volume and playing critical roles in transepithelial salt and water transport and in neuronal excitability. The function of these transporters has been intensively studied, but a mechanistic understanding has awaited structural studies of the transporters. Here, we present the cryo-electron microscopy (cryo-EM) structures of the two neuronal cation-chloride cotransporters human NKCC1 (SLC12A2) and mouse KCC2 (SLC12A5), along with computational analysis and functional characterization. These structures highlight essential residues in ion transport and allow us to propose mechanisms by which phosphorylation regulates transport activity.

Structures of eukaryotic ribonuclease P: Ribonuclease P (RNase P) is a ribozyme that processes transfer RNA (tRNA) precursors and is found in all three kingdoms of life. Now, Lan et al. report the structures of yeast RNase P (see the Perspective by Scott and Nagai). The aporibozyme structure reveals how the protein components stabilize the RNA and explains how the structural roles of bacterial RNA elements have been delegated to the protein components in RNase P of higher organisms during evolution. The structure of yeast RNase P in complex with its natural substrate, a tRNA precursor, demonstrates the structural basis for substrate recognition and provides insights into its catalytic mechanism. Science , this issue p. eaat6678 ; see also p. 644

Telomerase, a multi-subunit ribonucleoprotein complex, is a unique reverse transcriptase that catalyzes the processive addition of a repeat sequence to extend the telomere end using a short fragment of its own RNA component as the template. Despite recent structural characterizations of human and Tetrahymena telomerase, it is still a mystery how telomerase repeatedly uses its RNA template to synthesize telomeric DNA. Here, we report the cryo-EM structure of human telomerase holoenzyme bound with telomeric DNA at resolutions of 3.5 Å and 3.9 Å for the catalytic core and biogenesis module, respectively. The structure reveals that a leucine residue Leu980 in telomerase reverse transcriptase (TERT) catalytic subunit functions as a zipper head to limit the length of the short primer–template duplex in the active center. Moreover, our structural and computational analyses suggest that TERT and telomerase RNA (hTR) are organized to harbor a preformed active site that can accommodate short primer–template duplex substrates for catalysis. Furthermore, our findings unveil a double-fingers architecture in TERT that ensures nucleotide addition processivity of human telomerase. We propose that the zipper head Leu980 is a structural determinant for the sequence-based pausing signal of DNA synthesis that coincides with the RNA element-based physical template boundary. Functional analyses unveil that the non-glycine zipper head plays an essential role in both telomerase repeat addition processivity and telomere length homeostasis. In addition, we also demonstrate that this zipper head mechanism is conserved in all eukaryotic telomerases. Together, our study provides an integrated model for telomerase-mediated telomere synthesis.

Background: Robot-assisted surgery is increasingly used in children. While robot-assisted surgery in children has been proved to be safe and feasible, use in infants is controversial. The purpose of this study was to present a study of robot-assisted abdominal surgery in children less than5 months of age. Materials and methods: A retrospective analysis of 111 patients less than 5 months of age who underwent abdominal surgery from April 2020 to December 2022 in our hospital. The data included clinical information, operative details, and postoperative outcomes. Results: Among these 111 patients, 67 underwent robot-assisted surgery and 44 underwent laparoscopic-assisted surgery, the robot-assisted group includes 40 patients with Hirschsprung disease, 20 patients with choledochal cysts, and 7 patients with intestinal duplication, the laparoscopic-assisted group includes 26 patients with Hirschsprung disease, 9 patients with choledochal cysts, and 9 patients with intestinal duplication. For Hirschsprung disease, the operation time was significantly longer (P=0.013) and the intraoperative bleeding was significantly less (P=0.000) in the robot-assisted group than the laparoscopic assisted group. For choledochal cysts, the median operation time of 180 mins for the robot-assisted group was not significantly longer than the laparoscopic assisted surgery group at 160 mins (P=0.153). For intestinal duplication, the operation time was significantly longer (P=0.002) in the robot-assisted group than the laparoscopic assisted group. For these three diseases, the hospitalization expense was significantly higher (P0.05). Conclusion: Robot-assisted abdominal surgery in children less than 5 months of age is safe and feasible. This study showed that the surgical indications for the Da Vinci robot system in children can be extended to infants.

Enzymatic breakdown of sphingomyelin by sphingomyelinase (SMase) is the main source of the membrane lipids, ceramides, which are involved in many cellular physiological processes. However, the full-length structure of human neutral SMase has not been resolved; therefore, its catalytic mechanism remains unknown. Here, we resolve the structure of human full-length neutral SMase, sphingomyelinase 1 (SMPD2), which reveals that C-terminal transmembrane helices contribute to dimeric architecture of hSMPD2 and that D111 − K116 loop domain is essential for substrate hydrolysis. Coupled with molecular docking, we clarify the binding pose of sphingomyelin, and site-directed mutagenesis further confirms key residues responsible for sphingomyelin binding. Hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamic (MD) simulations are utilized to elaborate the catalysis of hSMPD2 with the reported in vitro substrates, sphingomyelin and lyso-platelet activating fator (lyso-PAF). Our study provides mechanistic details that enhance our knowledge of lipid metabolism and may lead to an improved understanding of ceramide in disease and in cancer treatment.