The role of the third extracellular loop of the Na+,K+-ATPase alpha subunit in a luminal gating mechanism.

Détails

ID Serval
serval:BIB_0CAB75E1B292
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
The role of the third extracellular loop of the Na+,K+-ATPase alpha subunit in a luminal gating mechanism.
Périodique
Journal of Physiology
Auteur(s)
Capendeguy O., Horisberger J.D.
ISSN
0022-3751
Statut éditorial
Publié
Date de publication
05/2005
Peer-reviewed
Oui
Volume
565
Numéro
Pt 1
Pages
207-218
Langue
anglais
Résumé
Na+,K+-ATPase is responsible for maintaining the cross-membrane Na+ and K+ gradients of animal cells. This P-type ATPase works via a complex transport cycle, during which it binds and occludes three intracellular Na+ ions and then two extracellular K+ ions, which it then releases on the other side of the membrane. The cation pathway through the protein, and the structures responsible for occluding cations inside the protein, have not yet been definitely identified. We used cysteine mutagenesis to explore the accessibility and the role of five conserved residues in the short third extracellular loop, between the fifth and the sixth transmembrane helices. The P801C and L802C mutants were not affected by extracellular sulfhydryl reagents. The presence of cysteine residues at three positions (G803C, T804C and V805C) conferred sensitivity to omeprazole, a known inhibitor of the gastric proton pump, and to [2-(trimethylammonium)-ethyl]methanethiosulphonate bromide (MTSET). The effects of omeprazole and MTSET were modulated by the presence of extracellular K+, indicating that the accessibility of these positions depended on the conformational state of the protein. MTSET binding to cysteine at position 803 partially inhibited the Na+,K+-pump function by decreasing its affinity towards extracellular K+, suggesting a restriction of the access of extracellular K+ ions to their binding sites. In contrast, MTSET binding to cysteine at position 805 partially inhibited the Na+,K+-pump function by reducing its maximum turnover rate, probably by slowing a rate-limiting conformational change. These residues occupy positions that are critical for either the cation pathway or the conformational modifications.
Mots-clé
Animals, Bufo marinus/genetics, Bufo marinus/metabolism, Cell Membrane/chemistry, Cell Membrane/physiology, Cells, Cultured, Cysteine/chemistry, Cysteine/metabolism, Ion Channel Gating/physiology, Membrane Potentials/physiology, Mutagenesis, Site-Directed, Oocytes/physiology, Protein Conformation, Protein Subunits, Recombinant Proteins/chemistry, Recombinant Proteins/metabolism, Sodium-Potassium-Exchanging ATPase/chemistry, Sodium-Potassium-Exchanging ATPase/genetics, Structure-Activity Relationship, Xenopus laevis
Pubmed
Web of science
Open Access
Oui
Création de la notice
24/01/2008 13:38
Dernière modification de la notice
20/08/2019 13:34
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