Effect of detergents on the chicken liver F1-ATPase: functional and structural aspects

The hydrolytic activity of the chicken liver F1-ATPase is strongly inhibited by detergents. The inhibition is concentration dependent and the highest value is obtained at the critical micelle concentration. Cationic and anionic detergents are good inhibitor of the enzyme, however the inhibition is correlated rather with the micelle size than the charge of the detergent as demonstrated by the inhibition observed with the non-ionic beta-D-alkyl glucosides. The effect of detergents upon subunits interactions was studied by trypsin limited proteolysis. Incubation with cholate results in the proteolytic cleavage of the alpha and gamma subunits whereas in the presence of DTAB also the beta subunit is digested. The small subunits delta and epsilon instead are not accessible when the enzyme is treated with both detergents. The results may suggest that hydrophobic areas of defined size located at the interface among alpha, beta and gamma subunit are crucial for the catalytic activity of the enzyme.