The properties of the binding of recombinant rat nucleoside diphosphate (NDP) kinase isoforms a and p (NDP kinase a and l$ respectively) to bleached bovine retinal rod outer segment (ROS) membranes were investigated. It was found that: (1) both NDP klnase isoforms interacted with ROS membranes in a pH-, cation-and GTP@dependent manner; (2) the retinal G-protein transducm was an obligatory factor for the interaction; (3) the apparent affhdty of NDP klnase a for ROS membranes was about loo-fold higher than that of NDP kinase fl; and (4) an a-isoform-specific peptlde, corresponding to the sequence of the N-terminal third (variable region), had the ability to displace bovine NDP khtase from ROS membranes. The results suggest the possible involvement of NDP kinases in cellular regulation via interaction with G-proteins and provide a structural basis for the possible differential roles of mammalian NDP khtase isoforms in the cell.

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