Mechanism of action of the calcium pump of sarcoplasmic reticulum of skeletal muscle.

The Ca2+-adenosine triphosphatase (ATPase) of skeletal muscle sarcoplasmic reticulum is a single protein species that pumps calcium ions at the expense of adenosine triphosphate (ATP). The reaction cycle includes phosphorylated intermediates which change the affinity and orientation of calcium sites. The monomer appears to be fully functional. Cross-linking and fluorescence studies indicate that ATP binds to a domain that approaches the phosphorylation site and becomes occluded during the reaction cycle. Interactions between these and the calcium channel, possibly via an energy transduction domain, ensure efficient coupling of catalytic and transport cycles.