Intracellular potassium promotes antibody binding to an antigen associated with the Na/K pump of sheep erythrocytes.
Anti-Lp antibody is known to bind to sheep red cells and to stimulate the Na/K pump. The antibody acts by reducing the affinity of the pumps for intracellular K as a noncompetitive inhibitor. We now show that intracellular K enhances the extent of anti-Lp binding to the pump-associated antigens. Cells made with approximately 60 mmol/1 K bound approximately 60% more anti-Lp than cells with O K; binding was assayed by measuring the extent of stimulation of the pump-mediated K influx.