How processing of aspartylphosphate is coupled to lumenal gating of the ion pathway in the calcium pump
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
-
Contributed by Chikashi Toyoshima, October 19, 2007 (received for review October 5, 2007)
Abstract
Ca2+-ATPase of skeletal muscle sarcoplasmic reticulum is the best-studied member of the P-type or E1/E2 type ion transporting ATPases. It has been crystallized in seven different states that cover nearly the entire reaction cycle. Here we describe the structure of this ATPase complexed with phosphate analogs BeF3 − and AlF4 − in the absence of Ca2+, which correspond to the E2P ground state and E2∼P transition state, respectively. The luminal gate is open with BeF3 − and closed with AlF4 −. These and the E1∼P·ADP analog crystal structures show that a two-step rotation of the cytoplasmic A-domain opens and closes the luminal gate through the movements of the M1–M4 transmembrane helices. There are several conformational switches coupled to the rotation, and the one in the cytoplasmic part of M2 has critical importance. In the second step of rotation, positioning of one water molecule couples the hydrolysis of aspartylphosphate to closing of the gate.
Footnotes
- *To whom correspondence should be addressed. E-mail: ct{at}iam.u-tokyo.ac.jp
-
Author contributions: C.T. designed research; C.T., S.I., and T.T. performed research; C.T., Y.N., and H.O. analyzed data; and C.T. wrote the paper.
-
The authors declare no conflict of interest.
-
Data deposition: The atomic coordinates for E1· AlF4 −·ADP, E2·BeF3 −(−TG), E2·BeF3 −(TG), and E2·AlF4 −(TG) forms of Ca2+-ATPase have been deposited in the Protein Data Bank, www.pdb.org (PDB ID codes 2ZBD, 2ZBE, 2ZBF and 2ZBG, respectively).
-
This article contains supporting information online at www.pnas.org/cgi/content/full/0709978104/DC1.
- © 2007 by The National Academy of Sciences of the USA
