Structural basis of ion pumping by Ca(2+)-ATPase of sarcoplasmic reticulum.

The structures of the Ca(2+)-ATPase (SERCA1a) have been determined for five different states by X-ray crystallography. Detailed comparison of the structures in the Ca(2+)-bound form and unbound (but thapsigargin-bound) form reveals that very large rearrangements of the transmembrane helices take place accompanying Ca2+ dissociation and binding and that they are mechanically linked with equally large movements of the cytoplasmic domains. The meanings of the rearrangements of the transmembrane helices and those of the cytoplasmic domains, and the mechanistic roles of the phosphorylation are now becoming clear.