Elucidation of IP6 and Heparin Interaction Sites and Conformational Changes in Arrestin-1 by Solution NMR

摘要

Arrestins specifically bind activated and phosphorylated G protein-coupled receptors, and orchestrate both receptor trafficking, and channel signaling to G protein-independent pathways via direct interactions with numerous non-receptor partners. Here we report the first successful use of solution NMR to map the binding sites in arrestin-1 (visual arrestin) for two polyanionic compounds that mimic phosphorylated light-activated rhodopsin: inositol hexaphosphate (IP6) and heparin. This yielded a more complete identification of residues involved in the binding with these ligands than has previously been feasible. IP6 and heparin appear to bind to the same site on arrestin-1, centered on a positively charged region in the N-domain. We present the first direct evidence that both IP6 and heparin induced a complete release of the arrestin C-tail. These observations provide novel insight into the nature of arrestin transition from basal to active state and demonstrate the potential of NMR-based methods in the study of protein-protein interactions involving members of the arrestin family.