The structure and interactions of Ca(2+)-ATPase.
Electron crystallographic studies on membrane crystals of Ca(2+)-ATPase reveal different patterns of ATPase-ATPase interactions depending on enzyme conformation. Physiologically relevant changes in Ca2+ concentration and membrane potential affect these interactions. Ca2+ induced difference FTIR spectra of Ca(2+)-ATPase triggered by photolysis of caged Ca2+ are consistent with changes in secondary structure and carboxylate groups upon Ca2+ binding; the changes are reversed during ATP hydrolysis suggesting that a phosphorylated enzyme form of low Ca2+ affinity is the dominant intermediate during Ca2+ transport. A two-channel model of Ca2+ translocation is proposed involving the membrane-spanning helices M2-M5 and M4, M5, M6 and M8 respectively, with separate but interacting Ca2+ binding sites.
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Department of Biochemistry and Molecular Biology, State University of New York, Syracuse 13210, USA.
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D011487:Protein Conformation
D000252:Calcium-Transporting ATPases