Binds to photoactivated, phosphorylated RHO and terminates RHO signaling via G-proteins by competing with G-proteins for the same binding site on RHO (PubMed:9333241, PubMed:16421323). May play a role in preventing light-dependent degeneration of retinal photoreceptor cells (PubMed:16421323). Monomer. Homodimer. Homotetramer (PubMed:21288033). Interacts with RHO (via the phosphorylated C-terminus) (PubMed:26200343, PubMed:28753425). Highly expressed in photoreceptor outer segments in light-exposed retina. Evenly distributed throughout rod photoreceptor cells in dark-adapted retina (By similarity). Predominantly dectected at the proximal region of photoreceptor outer segments, near disk membranes. Detected in retina (at protein level). The C-terminus interferes with binding to non-phosphorylated RHO. Interaction with phosphorylated RHO triggers displacement of the C-terminus and leads to a conformation change that mediates high-affinity RHO binding. The morphology of the retina is not affected when mice are kept in constant darkness. When mice are exposed to alternating 12 hour light and dark cycles, the rod photoreceptor outer segments are about 25% shorter than in wild-type, and the photoreceptor outer segments appear somewhat disordered (PubMed:9333241). After one year exposure to alternating 12 hour light and dark cycles, there are clear signs of photoreceptor degeneration with about 50% reduction in the number of photoreceptor nuclei in the outer layer of the retina (PubMed:16421323). Rod photoreceptor cells show normal flash sensitivity, but display prolonged RHO signaling, due to a strongly decreased rate of deactivation (PubMed:9333241, PubMed:16421323). Belongs to the arrestin family.