SERCA clears calcium from the muscle cytoplasm after each contraction. It binds two calcium ions on the cytoplasmic side and closes a gate. It phosphorylates itself with ATP, then opens a second gate to the lumen. Protons move the other way. One protein chain does all of this. It swings three cytoplasmic domains and rearranges ten membrane helices.
- Where
- Sarcoplasmic reticulum membrane of skeletal and cardiac muscle. Sister isoforms work in the endoplasmic reticulum of most animal cells, and in plant cells.
- Power
- Hydrolysis of one cytoplasmic ATP per transport cycle, with Mg2+ as cofactor
1 H+ per Ca2+
Proton counter-transport
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