[Protein inhibitor of the retinal cyclic nucleotide phosphodiesterase: its localization in the outer segment of a photoreceptor].

The content of a protein inhibitor of the cyclic nucleotides phosphodiesterase (PDE) in different retinal preparations as well as its distribution in the subfractions of rod outer segments (ROS) was studied. The content of protein inhibitor of PDE in different preparations of the retina was found to correlate with the rhodopsin content. The distribution of this protein over different ROS subfractions appeared to be exactly the same as that of rhodopsin, the content of protein inhibitor of PDE being more than a half of its content in the native ROS. The protein inhibitor of PDE could be easily washed out from the ROS fractions. It is concluded that the cattle protein inhibitor of PDE is localized in ROS, and is absent in the other retinal layers.