title: Saturation transfer electron spin resonance study on the rotational diffusion of calcium- and magnesium-dependent adenosine triphosphatase in sarcoplasmic reticulum membranes.
abstract: The technique of saturation transfer electron spin resonance has been applied to study the rotational diffusion of spin-labeled Ca2+, Mg2+-dependent ATPase molecules in the membranes of sarcoplasmic reticulum vesicles. Comparison of the present data with those for spin-labeled hemoglobin undergoing isotropic rotation leads to a value of 2 X 10(-4) s for the apparent rotational correlation time at 20 degrees C for the membrane-bound protein. Consideration of the anisotropy of the Brownian rotation of the membrane-bound ATPase suggests that the true correlation time for the expected axial rotation may be somewhat smaller than the apparent value. An Arrhenius plot of the rotational motion shows a break, which is interpreted as indicating the occurrence of a conformational change of the ATPase molecule at about 15 degrees C.
mesh_terms: D000251:Adenosine Triphosphatases; D000818:Animals; D000252:Calcium-Transporting ATPases; D004578:Electron Spin Resonance Spectroscopy; D007425:Intracellular Membranes / Q000201:enzymology; D008274:Magnesium / Q000494:pharmacology; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013113:Spin Labels; D013696:Temperature
chemical_list: D013113:Spin Labels; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases; D008274:Magnesium