Inaugural Article: Structural role of countertransport revealed in Ca2+ pump crystal structure in the absence of Ca2+.Obara, K., Miyashita, N., Xu, C., Toyoshima, I., Sugita, Y., Inesi, G., Toyoshima, C.
(2005) Proc.Natl.Acad.Sci.USA 102: 14489-14496
- PubMed: 16150713
- DOI: 10.1073/pnas.0506222102
- Also Cited By: 2ZBG, 2ZBF, 2ZBE, 2ZBD, 2Z9R, 2EAU, 2EAT, 2EAS, 2EAR, 2DQS
- PubMed Abstract:
- Crystal structure of the calcium pump of sarcoplasmic reticulum at 2.6 A resolution
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Ca(2+)-ATPase of sarcoplasmic reticulum is an ATP-powered Ca(2+) pump but also a H(+) pump in the opposite direction with no demonstrated functional role. Here, we report a 2.4-A-resolution crystal structure of the Ca(2+)-ATPase in the absence of Ca( ...
Ca(2+)-ATPase of sarcoplasmic reticulum is an ATP-powered Ca(2+) pump but also a H(+) pump in the opposite direction with no demonstrated functional role. Here, we report a 2.4-A-resolution crystal structure of the Ca(2+)-ATPase in the absence of Ca(2+) stabilized by two inhibitors, dibutyldihydroxybenzene, which bridges two transmembrane helices, and thapsigargin, also bound in the membrane region. Now visualized are water and several phospholipid molecules, one of which occupies a cleft between two transmembrane helices. Atomic models of the Ca(2+) binding sites with explicit hydrogens derived by continuum electrostatic calculations show how water and protons fill the space and compensate charge imbalance created by Ca(2+)-release. They suggest that H(+) countertransport is a consequence of a requirement for maintaining structural integrity of the empty Ca(2+)-binding sites. For this reason, cation countertransport is probably mandatory for all P-type ATPases and possibly accompanies transport of water as well.
Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.