Thermotropic transition in the states of proteins in sarcoplasmic reticulum vesicles

Interaction between protein and phospholipid molecules in sarcoplasmic reticulum (SR) was studied by measurement of the conformational fluctuation of the protein using the kinetics of the hydrogen-deuterium exchange reaction. It was revealed that the state of SR ATPase undergoes a phase transition at about 18 degrees C with boundary lipids, corresponding to a discrete change in the activation energy of the Ca2+, Mg2+-ATPase reaction.