title: Temperature-induced change in the Ca2+-dependent ATPase activity and in the state of the ATPase protein of sarcoplasmic reticulum membrane.
abstract: The temperature dependence of the Ca2+-dependent ATPase activity and of the conformational fluctuation of the ATPase molecule has been measured for four kinds of preparations: fragmented sarcoplasmic reticulum, MacLennan's enzyme (purified ATPase preparation), and DOL and egg PC-ATPase (purified ATPase preparations in which lipids are replaced with dioleoyllecithin and egg yolk lecithin, respectively). It has been found that Arrhenius plots of the Ca2+-dependent ATPase activity show a break at about 18 degrees C for all the preparations. Hydrogen--deuterium exchange kinetics of the peptide NH protons were used to measure the conformational fluctuation of the protein molecules. Van't Hoff plots of the conformational fluctuation amplitude of a region near the surface of the ATPase molecule also show a break at about 18 degrees C for all the preparations. It is concluded that the break at around 18 degrees C is not related to a gel-liquid crystalline transition of lipids but to a change in the conformation of the ATPase molecule existing in fluid lipids.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D007425:Intracellular Membranes / Q000201:enzymology; D007700:Kinetics; D009132:Muscles / Q000201:enzymology; D010743:Phospholipids / Q000032:analysis; D011487:Protein Conformation; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013696:Temperature
chemical_list: D010743:Phospholipids; D000251:Adenosine Triphosphatases; D000252:Calcium-Transporting ATPases