[Mechanism of ca(2+) pump as revealed by mutations, development of stable analogs of phosphorylated intermediates, and their structural analyses].
Sarco(endo)plasmic reticulum Ca(2+)-ATPase is a representative member of P-type cation transporting ATPases and catalyzes Ca(2+) transport coupled with ATP hydrolysis. The ATPase possesses three cytoplasmic domains (N, P, and A) and ten transmembrane helices (M1-M10). Ca(2+) binding at the transport sites in the transmembrane domain activates the ATPase and then the catalytic aspartate is auto-phosphorylated to form the phosphorylated intermediate (EP). Structural and functional studies have shown that, during the isomerization of EP in the Ca(2+) transport cycle, large motions of the three cytoplasmic domains take place, which then rearranges the transmembrane helices thereby destroying the Ca(2+) binding sites, opening the lumenal gate, and thus releasing the Ca(2+) into lumen. Stable structural analogues for the Ca(2+)-occluded and -released states of phosphorylated intermediates and for the transition and product states of the phosphorylation and dephosphorylation reactions were developed for biochemical and atomic-level structural studies to reveal the coupled changes in the catalytic and transport sites. Mutation studies identified the residues and structural regions essential for the structural changes and Ca(2+) transport function. Genetic dysfunction of Ca(2+)-ATPase causes various isoform-specific diseases. In this manuscript, recent understanding of the Ca-ATPase will be reviewed.
Suzuki
Hiroshi
H
Department of Biochemistry, Asahikawa Medical College, Hokkaido, Japan. hisuzuki@asahikawa-med.ac.jp
Yamasaki
Kazuo
K
Daiho
Takashi
T
Danko
Stefania
S
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D002384:Catalysis; D007644:Darier Disease / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006801:Humans; D009154:Mutation; D010766:Phosphorylation; D017434:Protein Structure, Tertiary
D000252:Calcium-Transporting ATPases; D002118:Calcium