MOLECULAR-CLONING AND CHARACTERIZATION OF RETINAL PHOTORECEPTOR GUANYLYL CYCLASE-ACTIVATING PROTEIN

Guanylyl cyclase-activating protein (GCAP) is thought to mediate Ca2+- sensitive regulation of guanylyl cyclase (GC), a key event in recovery of the dark state of rod photoreceptors following light exposure. Her e, we characterize GCAP from several vertebrate species by molecular c loning and provide evidence that GCAP contains a heterogeneously acyla ted N-terminal region that interacts with GC. Vertebrate GCAPs consist of 201-205 amino acids, and sequence analysis indicates the presence of three EF hand Ca2+-binding motifs. These results establish that GCA P is a novel photoreceptor-specific member of a large family of Ca2+-b inding proteins and suggest that it participates in the Ca2+-sensitive activation of GC.