Crystal structures of Ca2+-ATPase in various physiological states.

The structures of the Ca(2+)-ATPase (SERCA1a) in different physiological states were determined 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 Ca(2+) dissociation and binding and that they are mechanically linked with equally large movements of the cytoplasmic domains. The meaning of the rearrangement of the transmembrane helices becomes apparent by homology modeling of the Na(+)K(+)-ATPase.