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Spectroscopy
Volume 22 (2008), Issue 2-3, Pages 63-82
http://dx.doi.org/10.3233/SPE-2008-0342

Structural dynamics of the Ca2+-ATPase studied by time-resolved infrared spectroscopy

Andreas Barth

Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, S-106 91 Stockholm, Sweden

Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This review discusses the contribution of time-resolved infrared spectroscopy to the understanding of the Ca2+ pump in the sarcoplasmic reticulum membrane of skeletal muscle cells (SERCA1a). The focus is on interactions of the substrate ATP with the ATPase and on the bond parameters of the phosphoenzyme phosphate group. Functional groups throughout the ATP molecule are important for stabilising the closed conformation of the ATP–ATPase complex and for fast phosphorylation of the ATPase. Dissociation of the reaction product ADP after phosphorylation leads to a more open average conformation of the enzyme and does not trigger the transition from the first phosphoenzyme Ca2E1P to the second E2P. The P–O bond between phosphate and aspartyl moieties is weaker in Ca2E1P and E2P than in acetyl phosphate in aqueous solution, which explains the high reactivity of the phosphoenzymes. This ground state property of the phosphoenzymes prepares for a phosphate transfer reaction with dissociative character.