Involvement of the alpha-subunit N-terminus in the mechanism of the Na + ,K + -ATPase.

Autor: Lev B; School of Science, RMIT University, Melbourne, Vic, 3001, Australia., Chennath M; School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia., Cranfield CG; School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia., Cornelius F; Department of Biomedicine, University of Aarhus, DK-8000 Aarhus, C, Denmark., Allen TW; School of Science, RMIT University, Melbourne, Vic, 3001, Australia., Clarke RJ; School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, Sydney, NSW 2006, Australia. Electronic address: ronald.clarke@sydney.edu.au.
Jazyk: angličtina
Zdroj: Biochimica et biophysica acta. Molecular cell research [Biochim Biophys Acta Mol Cell Res] 2023 Oct; Vol. 1870 (7), pp. 119539. Date of Electronic Publication: 2023 Jul 20.
DOI: 10.1016/j.bbamcr.2023.119539
Abstrakt: Previous studies have shown that cytoplasmic K + release and the associated E2 → E1 conformational change of the Na + ,K + -ATPase is a major rate-determining step of the enzyme's ion pumping cycle and hence a prime site of acute regulatory intervention. From the ionic strength dependence of the enzyme's distribution between the E2 and E1 states, it has also been found that E2 is stabilized by an electrostatic attraction. Any disruption of this electrostatic attraction would, thus, have profound effects on the rate of ion pumping. The aim of this paper is to identify the location of this interaction. Using enhanced-sampling molecular dynamics simulations with a predicted N-terminal structure added to the X-ray crystal structure of the Na + ,K + -ATPase, a previously postulated salt bridge between Lys32 and Glu233 (rat sequence numbering) of the enzyme's α-subunit can be excluded. The residues never approach closely enough to form a salt bridge. In contrast, strong interactions with anionic lipid head groups were seen. To investigate the possibility of a protein-lipid interaction experimentally, the surface charge density of Na + ,K + -ATPase-containing membrane fragments was estimated from zeta potential measurements to be 0.019 (± 0.001) C m -2 . This is in good agreement with the charge density previously determined to be responsible for stabilization of the E2 state of 0.023 (± 0.009) C m -2 and the membrane charge density estimated here from published electron-microscopic images of 0.018C m -2 . The results are, therefore, consistent with an interaction of the Na + ,K + -ATPase α-subunit N-terminus with negatively-charged lipid head groups of the neighbouring cytoplasmic membrane surface as the origin of the electrostatic interaction stabilising the E2 state.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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