Modification of (Na+,K+)-ATPase function by purified antibodies to the holoenzyme. Effects on enzyme activity and (3H)ouabain binding.

Antibodies (abys) raised to (Na+,K+)-ATPase were purified by elution methods and shown to be cross-reactive with anti-gamma-globulin and the original antigen. Abys were isolated from two different antisera and the effects on (Na+,K+)-ATPase hydrolytic activity and 3H]ouabain binding were measured. The antisera fractions differed as to their maximum level of inhibition of hydrolytic activity and maximal 3H]ouabain binding, but both fractions caused inhibition of maximal 3H]ouabain binding to the same quantitative extent as inhibition of hydrolytic activity. Variable effects on the rate of 3H]ouabain binding were noted which were highly dependent on ligand conditions. During the "turnover state conditions" of the enzyme, the abys stimulated the rate of 3H]ouabain binding to the (Na+,K+)-ATPase. We conclude that effects of aby-(Na+,K+)-ATPase interaction depend upon degree of purity of aby, specificity, aby/enzyme ratios, and ligand conditions.