MECHANISM OF THERMAL UNCOUPLING OF THE SARCOPLASMIC-RETICULUM CA2-PUMP - CHANGE IN FUNCTIONAL-PROPERTIES AND STRUCTURAL STATE OF THE ENZYMEMOLECULE()

The effect of short thermal treatment resulting in uncoupling of hydro lytic and transport functions of skeletal muscle sarcoplasmic reticulu m Ca2+-ATPase on the conformational state of the enzyme and the physic ochemical parameters of the membrane lipid bilayer was investigated It was found that the main reason for the decrease in efficiency of the Ca2+-pump is the increase in membrane permeability for Ca2+. No change in Ca2+-ATPase hydrophilic domain conformation was found after therma l treatment. However, thermal treatment restricts the accessibility of the transmembrane hydrophobic domain of the enzyme to several compoun ds, decreases microviscosity of the lipid bilayer, and modifies protei n-lipid and protein-protein interactions in the membrane.