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:8003967, PubMed:25205354). May play a role in preventing light-dependent degeneration of retinal photoreceptor cells (By similarity). Monomer (PubMed:21288033). Homodimer (PubMed:21288033, PubMed:10219246, PubMed:26510463). Homotetramer (PubMed:21288033, PubMed:10219246). Self-association is cooperative (PubMed:21288033). Isoform A and isoform B interact with RHO (via phosphorylated C-terminus) (PubMed:8003967, PubMed:10219246, PubMed:23604253, PubMed:25205354). Highly expressed in photoreceptor outer segments in light-exposed retina (PubMed:7515057). Evenly distributed throughout rod photoreceptor cells in dark-adapted retina (PubMed:7515057). Predominantly dectected at the proximal region of photoreceptor outer segments, near disk membranes (By similarity). Detected in retina, in rod photoreceptor cells (at protein level) (PubMed:7515057, PubMed:8003967). The C-terminus of isoform A 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. Isoform B is C-terminally truncated and is therefore already in the optimal conformation for RHO binding. Belongs to the arrestin family.