Active sites of the cyclic GMP phosphodiesterase gamma-subunit of retinal rod outer segments.

Monoclonal antibodies were prepared to the gamma-subunit of the cGMP phosphodiesterase. One of them gamma p-1, suppresses the activation of phosphodiesterase through the alpha-subunit of transducin. The gamma-subunit fragment 24-45 rich in Arg and Lys residues is involved in gamma p-1 binding and is essential for the gamma-subunit interaction with transducin. Carboxypeptidase Y cleaves off seven amino acid residues from the C-terminus of the gamma-subunit resulting in phosphodiesterase activation. Thus, the C-terminal fragment of gamma-subunit participates in phosphodiesterase inhibition.