Ion pump in the movies

摘要

Insight into how membrane ion pumps work requires structural snapshots of various stages of their catalytic cycle. Now a fifth freeze-frame image of a calcium pump in action adds to a striking body of work on this protein. On page 361 of this issue, Toyoshima and colleagues reveal the latest in a series of high-resolution, three-dimensional snapshots of an ion pump at work. The pump in question is powered by adenosine triphosphate (ATP) molecules and moves calcium ions across biological membranes --an activity that is crucial for skeletal muscle to function. Comparison of this structural snapshot with images of other stages of the pump's catalytic cycle provides an almost-complete movie of its mechanism.