Nitric Oxide-Regulated Endogenous ADP-Ribosylation of Rod Outer Segment Proteins

Abstract

Both membrane and cytosolic fractions of retinal rod outer segments contain ADP-ribosylases that modify proteins in the respective fractions. Nitroprusside and endogenously produced NO regulate the activities of these ADP-robosylases. The ADP-ribosylation of the membrane proteins of molecular weight 116K, 66K and 46K is inhibited by NO and nitroprusside, while that of the 38K cytosolic protein and the 39K membrane-associated protein is activated. The 39K protein is identified as the α-subunit of G-protein. The ADP-ribosylation of this protein is activated 6 to 11-fold by NO suggesting that NO may play a significant role in modulating the activity of G-protein in visual transduction.