Electron crystallographic studies on membrane crystals of Ca2+-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 Ca2+-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.
Review Article| October 01 1995
The structure and interactions of Ca2+-ATPase
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Anthony N. Martonosi; The structure and interactions of Ca2+-ATPase. Biosci Rep 1 October 1995; 15 (5): 263–281. doi: https://doi.org/10.1007/BF01788359
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