Structural highlights
8ijl is a 2 chain structure with sequence from Rattus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
|
| Method: | Electron Microscopy, Resolution 2.62Å |
| Ligands: | , , , , , , , |
| Resources: | FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT |
Function
AT12A_RAT The catalytic subunit of a H(+)/K(+) ATPase and/or Na(+)/K(+) ATPase pump which transports K(+) ions in exchange for Na(+) and/or H(+) ions across the apical membrane of epithelial cells. Uses ATP as an energy source to pump K(+) ions into the cell while transporting Na(+) and/or H(+) ions to the extracellular compartment (PubMed:10644526, PubMed:7560093). Involved in the maintenance of electrolyte homeostasis through K(+) ion absorption in kidney and colon (By similarity). In the airway epithelium, may play a primary role in mucus acidification regulating its viscosity and clearance (By similarity).[UniProtKB:P54707][UniProtKB:Q9Z1W8][1] [2]
Publication Abstract from PubMed
The Na(+),K(+)-ATPase (NKA) and non-gastric H(+),K(+)- ATPase (ngHKA) share ~65 % sequence identity, and nearly identical catalytic cycles. These pumps alternate between inward-facing (E1) and outward-facing (E2) conformations and differ in their exported substrate (Na(+) or H(+)) and stoichiometries (3 Na(+):2 K(+) or 1 H(+):1 K(+)). We reported that structures of the NKA-mimetic ngHKA mutant K794S/A797P/W940/R949C (SPWC) with 2 K(+) occluded in E2-P(i) and 3 Na(+)-bound in E1.ATP states were nearly identical to NKA structures in equivalent states. Here we report the cryo-EM structures of K794A and K794S, two poorly-selective ngHKA mutants, under conditions to stabilize the E1.ATP state. Unexpectedly, the structures show a hybrid with both E1- and E2-like structural features. While transmembrane segments TM1-TM3 and TM4's extracellular half adopted an E2-like conformation, the rest of the protein assumed an E1 configuration. Two spherical densities, likely bound Na(+), were observed at cation-binding sites I and III, without density at site II. This explains the E2-like conformation of TM4's exoplasmic half. In NKA, oxygen atoms derived from the unwound portion of TM4 coordinated Na(+) at site II. Thus, the lack of Na(+) at site II of K794A/S prevents the luminal portion of TM4 from taking an E1-like position. The K794A structure also suggests that incomplete coordination of Na(+) at site III induces the halfway rotation of TM6, which impairs Na(+)-binding at the site II. Thus, our observations provide insight into the molecular mechanism of E2-E1 transition and cooperative Na(+)-binding in the NKA and other related cation pumps.
An unusual conformation from Na(+)-sensitive non-gastric proton pump mutants reveals molecular mechanisms of cooperative Na(+)-binding.,Abe K, Nishizawa T, Artigas P Biochim Biophys Acta Mol Cell Res. 2023 Oct;1870(7):119543. doi: , 10.1016/j.bbamcr.2023.119543. Epub 2023 Jul 22. PMID:37482134[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Sangan P, Thevananther S, Sangan S, Rajendran VM, Binder HJ. Colonic H-K-ATPase alpha- and beta-subunits express ouabain-insensitive H-K-ATPase. Am J Physiol Cell Physiol. 2000 Jan;278(1):C182-9. doi:, 10.1152/ajpcell.2000.278.1.C182. PMID:10644526 doi:http://dx.doi.org/10.1152/ajpcell.2000.278.1.C182
- ↑ Lee J, Rajendran VM, Mann AS, Kashgarian M, Binder HJ. Functional expression and segmental localization of rat colonic K-adenosine triphosphatase. J Clin Invest. 1995 Oct;96(4):2002-8. doi: 10.1172/JCI118247. PMID:7560093 doi:http://dx.doi.org/10.1172/JCI118247
- ↑ Abe K, Nishizawa T, Artigas P. An unusual conformation from Na(+)-sensitive non-gastric proton pump mutants reveals molecular mechanisms of cooperative Na(+)-binding. Biochim Biophys Acta Mol Cell Res. 2023 Oct;1870(7):119543. PMID:37482134 doi:10.1016/j.bbamcr.2023.119543
