The selectivity of visual arrestin for light-activated phosphorhodopsin is controlled by multiple nonredundant mechanisms.
Arrestin plays an important role in quenching phototransduction via its ability to bind to the phosphorylated light-activated form of the visual receptor rhodopsin (P-Rh*). Remarkable selectivity of visual arrestin toward this functional form is determined by an elegant sequential multisite binding mechanism. Previous structure-function studies have suggested that the COOH-terminal region of arrestin (residues 356-404) is not directly involved in rhodopsin interaction, but instead plays a regulatory role. This region supports basal arrestin conformation and ensures arrestin's transition into a high affinity rhodopsin-binding state upon an encounter with P-Rh*. Overall, our results corroborate this hypothesis and identify three functional subregions (residues 361-368, 369-378, and 379-404) and individual amino acids involved in the control of arrestin stability and binding selectivity. Two of the most potent mutants, arrestin(1-378) and arrestin(F375A,V376A, F377A) belong to a novel class of constitutively active arrestins with high affinity for P-Rh*, dark P-Rh, and Rh* (but not dark Rh), in contrast to earlier constructed mutants arrestin(R175E) and arrestin(Delta2-16) with high affinity for light-activated forms only. The implications of these findings for the mechanism of arrestin-rhodopsin interaction are discussed in light of the recently determined crystal structure of arrestin.
Gurevich
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Sun Health Research Institute, Sun City, Arizona 85372, USA. vgurevich@sunhealth.org
D000595:Amino Acid Sequence; D000818:Animals; D019393:Arrestin / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002417:Cattle; D018360:Crystallography, X-Ray; D005136:Eye Proteins; D051606:G-Protein-Coupled Receptor Kinase 1; D006801:Humans; D008027:Light; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism*; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
D019393:Arrestin; D005136:Eye Proteins; D012243:Rhodopsin; D011494:Protein Kinases; D051606:G-Protein-Coupled Receptor Kinase 1; C496764:GRK1 protein, human