title: Critical role of the central 139-loop in stability and binding selectivity of arrestin-1.
abstract: Arrestin-1 selectively binds active phosphorylated rhodopsin (P-Rh*), demonstrating much lower affinity for inactive phosphorylated (P-Rh) and unphosphorylated active (Rh*) forms. Receptor interaction induces significant conformational changes in arrestin-1, which include large movement of the previously neglected 139-loop in the center of the receptor binding surface, away from the incoming receptor. To elucidate the functional role of this loop, in mouse arrestin-1 we introduced deletions of variable lengths and made several substitutions of Lys-142 in it and Asp-72 in the adjacent loop. Several mutants with perturbations in the 139-loop demonstrate increased binding to P-Rh*, dark P-Rh, Rh*, and phospho-opsin. Enhanced binding of arrestin-1 mutants to non-preferred forms of rhodopsin correlates with decreased thermal stability. The 139-loop perturbations increase P-Rh* binding of arrestin-1 at low temperatures and further change its binding profile on the background of 3A mutant, where the C-tail is detached from the body of the molecule by triple alanine substitution. Thus, the 139-loop stabilizes basal conformation of arrestin-1 and acts as a brake, preventing its binding to non-preferred forms of rhodopsin. Conservation of this loop in other subtypes suggests that it has the same function in all members of the arrestin family.
authors.affiliation: Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Vishnivetskiy
authors.forename: Faiza
authors.initials: F
authors.lastname: Baameur
authors.forename: Kristen R
authors.initials: KR
authors.lastname: Findley
authors.forename: Vsevolod V
authors.initials: VV
authors.lastname: Gurevich
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D019390:Arrestins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002417:Cattle; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D011485:Protein Binding / Q000502:physiology; D055550:Protein Stability; D017433:Protein Structure, Secondary; D051381:Rats; D017299:Rod Opsins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D017299:Rod Opsins; D000071557:beta-Arrestins; C059623:phosphoopsin