Conformation of receptor-bound visual arrestin.

Kim M, Vishnivetskiy SA, Van Eps N, Alexander NS, Cleghorn WM, Zhan X, Hanson SM, Morizumi T, Ernst OP, Meiler J, Gurevich VV, Hubbell WL
Proc Natl Acad Sci U S A. 2012 109 (45): 18407-12

PMID: 23091036 · PMCID: PMC3494953 · DOI:10.1073/pnas.1216304109

Arrestin-1 (visual arrestin) binds to light-activated phosphorylated rhodopsin (P-Rh*) to terminate G-protein signaling. To map conformational changes upon binding to the receptor, pairs of spin labels were introduced in arrestin-1 and double electron-electron resonance was used to monitor interspin distance changes upon P-Rh* binding. The results indicate that the relative position of the N and C domains remains largely unchanged, contrary to expectations of a "clam-shell" model. A loop implicated in P-Rh* binding that connects β-strands V and VI (the "finger loop," residues 67-79) moves toward the expected location of P-Rh* in the complex, but does not assume a fully extended conformation. A striking and unexpected movement of a loop containing residue 139 away from the adjacent finger loop is observed, which appears to facilitate P-Rh* binding. This change is accompanied by smaller movements of distal loops containing residues 157 and 344 at the tips of the N and C domains, which correspond to "plastic" regions of arrestin-1 that have distinct conformations in monomers of the crystal tetramer. Remarkably, the loops containing residues 139, 157, and 344 appear to have high flexibility in both free arrestin-1 and the P-Rh*complex.

MeSH Terms (15)

Arrestin Crystallography, X-Ray Electrons Models, Molecular Mutant Proteins Phosphorylation Protein Binding Protein Multimerization Protein Stability Protein Structure, Secondary Rhodopsin Sequence Deletion Solutions Staining and Labeling Temperature

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