Localization of a K+ -binding site involved in dephosphorylation of the sarcoplasmic reticulum Ca2+ -ATPase
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Updated: Aug 22, 2026

Purification of the Sarco-Endoplasmic Reticulum Ca2+-ATPase from Rabbit Muscle
Published on: March 21, 2025
Thomas Lykke-Møller Sørensen1, Johannes D Clausen, Anne-Marie Lund Jensen
1Centre for Structural Biology, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Abstract:
K+ plays an important role for the function of the sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA), but its binding site within the molecule has remained unidentified. We have located the binding site for a K+ ion in the P-domain by means of x-ray crystallography using crystals prepared in the presence of the K+ congener Rb+. Backbone carbonyls from the loop containing residues 711-715 together with the side chain of Glu732 define the K+/Rb+ site in the Ca2+ -ATPase conformation with bound Ca2+, ADP, and AlF4-. Functional analysis of Ca2+ -ATPase mutants with alterations to Glu732 shows that this site is indeed important for the stimulatory effect of K+ on the dephosphorylation rate. Comparison with the Ca2+ -ATPase in a dephosphorylated E2 conformation suggests that the K+ site is involved in the correct movement and positioning of the A-domain during translocation and dephosphorylation.
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