PURIFIED RETINAL NITRIC-OXIDE SYNTHASE ENHANCES ADP-RIBOSYLATION OF ROD OUTER SEGMENT PROTEINS

Nitric oxide synthase is present in different cell layers of vertebrat e retina and seems to have neuromodulatory functions in the outer reti na, The enzyme, when purified from a bovine retina extract, has an app arent molecular mass of 160 kDa and resembles the neuronal constitutiv e NOS type I with respect to Ca2+-calmodulin sensitivity, K-m value an d inhibition by analogues of L-arginine. Retinal NOS is present in a p reparation of rod outer segments attached to parts of the inner segmen ts, but not in pure outer segments. We describe the enhancement of spe cific ADP-ribosylation of outer segment proteins by purified retinal N OS.