ARRESTIN INTERACTIONS WITH G-PROTEIN-COUPLED RECEPTORS - DIRECT BINDING-STUDIES OF WILD-TYPE AND MUTANT ARRESTINS WITH RHODOPSIN, BETA(2)-ADRENERGIC, AND M2-MUSCARINIC CHOLINERGIC RECEPTORS

Arrestins play an important role in quenching signal transduction init iated by G protein-coupled receptors. To explore the specificity of ar restin-receptor interaction, we have characterized the ability of vari ous wildtype arrestins to bind to rhodopsin, the beta(2)-adrenergic re ceptor (beta(2)AR), and the m2 muscarinic cholinergic receptor (m2 mAC hR), Visual arrestin was found to be the most selective arrestin since it discriminated best between the three different receptors tested (h ighest binding to rhodopsin) as web as between the phosphorylation and activation state of the receptor (>10-fold higher binding to the phos phorylated Light-activated form of rhodopsin compared to any other for m of rhodopsin). While beta-arrestin and arrestin 3 were also found to preferentially bind to the phosphorylated activated form of a given r eceptor, they only modestly discriminated among the three receptors te sted. To explore the structural characteristics important in arrestin function, we constructed a series of truncated and chimeric arrestins. Analysis of the binding characteristics of the various mutant arresti ns suggests a common molecular mechanism involved in determining recep tor binding selectivity. Structural elements that contribute to arrest in binding include: 1) a C-terminal acidic region that serves a regula tory role in controlling arrestin binding selectivity toward the phosp horylated and activated form of a receptor, without directly participa ting in receptor interaction; 2) a basic N-terminal domain that direct ly participates in receptor interaction and appears to serve a regulat ory role via intramolecular interaction with the C-terminal acidic reg ion; and 3) two centrally localized domains that are directly involved in determining receptor binding specificity and selectivity. A compar ative structure-function model of all arrestins and a kinetic model of beta-arrestin and arrestin 3 interaction with receptors are proposed.