Interaction of phosphoglycerate kinase with human erythrocyte membranes

The purpose of this study was to investigate the interaction of phosphoglycerate kinase with the human erythrocyte ghost membrane. Ghosts prepared in 0.1 mM EDTA and 17 mM Tris buffer (pH 7.5) have about 230 molecules of phosphoglycerate kinase/ghost. No additional binding is observed after incubating soluble enzyme with these leaky ghosts. This binding is tight but reversible with Kd = 7.1 x 10^-10 M. The enzyme can be eluted significantly from the membrane by incubation with 0.15 M NaCl and it rebinds to the membrane when the depleted ghosts are incubated with rabbit muscle phosphoglycerate kinase. Ligand binding studies show that NADH and NAD have opposite effects on the binding of the enzyme to the membrane; NAD (1.0 mM) favors binding while NADH (0.25 mM) does not. Similarly, ADP (0.2 mM) favors binding while ATP does not. ATP elutes the membrane-bound enzyme with Kd = 0.058 mM. MgSO₄ also stimulates dissociation of the mebrane-bound phosphoglycerate kinase (Kd = 0.36 mM), an effect which appears to be due to the magnesium ion. ADP (0.2 mM) can counteract the negative effect of MgSO₄ (1.0 mM) on binding of phosphoglycerate kinase to the membrane. We have been unable so far to find tight coupling of the (Na⁺-K⁺)-ATPase with the membrane-bound phosphoglycerate kinase.