The sequence of arrestins from rod and cone photoreceptors in the frogs Rana catesbeiana and Rana pipiens. Localization of gene transcripts by reverse-transcription polymerase chain reaction on isolated photoreceptors.

Members of the arrestin protein family are known to participate in the inactivation of rhodopsin and other heptahelical receptors. Arrestins bind to the activated and phosphorylated state of these receptors, consequently blocking the ability of the receptors to activate the guanine-nucleotide-binding protein (G protein). We have determined the sequences of four retinal arrestins from two species of frog, Rana catesbeiana and Rana pipiens. Using polymerase chain reaction on reverse-transcribed mRNA isolated from single photoreceptor cells, we show that two of these arrestins are from rod photoreceptors and two rod photoreceptors and two are from cone photoreceptors. Comparison of these arrestins with the twenty known arrestin sequences identifies three regions of the protein that are well conserved across all phylogenetic groups. These regions may function in the binding of the arrestin to the heptahelical receptors. In addition, the Rana arrestins contain a uniquely acidic C-terminal sequence.