Interaction of nucleoside diphosphate kinase with membranes of the bleached bovine retinal rod outer segments. effect of pH, salts, and guanine nucleotides

摘要

It was shown that soluble nucleoside diphosphate (NDP) kinase in the purified bovine retinal rod outer segment (ROS) preparations exhibits equilibrium binding to the bleached photoreceptor membranes. The binding is under the control of pH and concentration of salts (NaCl, KCl, CaCl_2, or MgCl_2). Acidic pH and low ionic strength favor the membrane-bound form. The membrane-bound NDP kinase is released in the presence of low concentrations of guanosine 5'-O-(3-thio)triphosphate (GTP[S]), GTP, and other related compounds. Whereas adenosine 5'-(#beta#, #gamma#-imino)triphosphate is ineffective under the similar conditions. The binding of NDP kinase to the bleached ROS membranes required the presence ROS G-protein transducin (G_t). G_t-depleted ROS membranes were still able to bind NDP kinase, whereas its apparent affinity was weak and unaffected by GTP[S]. These results imply that GTP[S]-dependent interaction of NDP kinase with the mebranes in the presence the bleached visual pigment rhodopsin is mediated by G_t. The possibility of participation of NDP kinase in extremely rapid photoactivation of G_t in living ROS is duscussed.