Affinity labeling of the (Na+ + Mg2+)-ATPase from Acholeplasma laidlawii B membranes by the 2',3'-dialdehyde derivative of adenosine 5'-triphosphate

The (Na+ + Mg2+)-ATPase of the Acholeplasma laidlawii B plasma membrane was inactivated by the 2',3'-dialdehyde derivative of ATP (oATP). oATP behaved as a reversible competitive inhibitor of this ATPase and was slowly hydrolyzed by the enzyme. In addition, oATP induced an irreversible inactivation of the enzyme. A 62% inactivation of the enzyme correlated with the binding of 16 moles of oATP per mole of the enzyme. In the presence of 5'-adenylyl imidodiphosphate, a non-hydrolyzable substrate analogue, the stoichiometry was 8 moles oATP per mole of ATPase. By SDS-polyacrylamide gel electrophoresis, U-14C]oATP was found to bind covalently to four of the five subunits of the enzyme, but specific labeling was highest for the gamma-subunit of the ATPase.