[Methylation of 3',5'-cGMP phosphodiesterase in retinal photoreceptor membranes]

It was found that the level of methylation of phosphodiesterase (EC 3.1.4.17) and of proteins with Mr 61000 and 21000-26000 Da in isolated preparations of bovine retinal outer segments was sharply increased in the presence of cGMP, but not with cAMP. Preparations of the outer segment phosphodiesterase protein inhibitor, which inhibits the cyclic nucleotide hydrolysis, significantly decreased the methylation level. The degree of the enzyme methylation depended on the functional state of the outer segments: in light-induced preparations it was higher that in the dark ones.