Roles of transmembrane segment M1 of Na(+),K (+)-ATPase and Ca (2+)-ATPase, the gatekeeper and the pivot.

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    In this review we summarize mutagenesis work on the structure-function relationship of transmembrane segment M1 in the Na(+),K(+)-ATPase and the sarco(endo)plasmic reticulum Ca(2+)-ATPase. The original hypothesis that charged residues in the N-terminal part of M1 interact with the transported cations can be rejected. On the other hand hydrophobic residues in the middle part of M1 turned out to play crucial roles in Ca(2+) interaction/occlusion in Ca(2+)-ATPase and K(+) interaction/occlusion in Na(+),K(+)-ATPase. Leu(65) of the Ca(2+)-ATPase and Leu(99) of the Na(+),K(+)-ATPase, located at homologous positions in M1, function as gate-locking residues that restrict the mobility of the side chain of the cation binding/gating residue of transmembrane segment M4, Glu(309)/Glu(329). A pivot formed between a pair of a glycine and a bulky residue in M1 and M3 seems critical to the opening of the extracytoplasmic gate in both the Ca(2+)-ATPase and the Na(+),K(+)-ATPase.
    Udgivelsesdato: 2007-Dec
    TidsskriftJournal of Bioenergetics and Biomembranes
    Sider (fra-til)357-366
    Antal sider9
    StatusUdgivet - 2007