Large-Scale Structural Changes in the Sarcoplasmic Reticulum ATP-ASE are Essential for Calcium Active Transport
The active (energy-dependent) transport of calcium from the cytoplasm across the sarcoplasmic reticulum (SR) membrane into the sarcotubular system by the membrane Ca2+ATPase is responsible for the relaxation phase of the contraction-relaxation cycle in striated and cardiac muscle (Ebashi et al., 1969). Since the sarcoplasmic retículum membrane can be isolated in the form of closed unilamellar vesicles in which the Ca2+ATPase comprises over 90% of the membrane protein (Meissner et al., 1973), the enzyme catalyzed chemical reactions involved in the calcium active transport process (DeMeis and Vienna, 1979), and the structure and organization of the membrane components (Blasie et al., 1985) have been relatively well characterized. As a result, this system provides an excellent prototype for the study of the critical structure-function relationships involved in the active transport of ions across biological membranes.
KeywordsSarcoplasmic Reticulum Flash Photolysis Sarcoplasmic Reticulum Membrane Membrane Profile Stanford Synchrotron Radiation Laboratory
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