Open AccessThe solution structure and activation of visual arrestin studied by small‐angle X‐ray scattering
Author(s) -
Shilton Brian H.,
McDowell J. Hugh,
Smith W. Clay,
Hargrave Paul A.
Publication year - 2002
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2002.03071.x
Subject(s) - arrestin , phosphopeptide , small angle x ray scattering , rhodopsin , dimer , crystallography , chemistry , dissociation constant , biophysics , mutant , stereochemistry , phosphorylation , scattering , biochemistry , biology , signal transduction , receptor , g protein coupled receptor , physics , retinal , optics , organic chemistry , gene
Visual arrestin is converted from a ‘basal’ state to an ‘activated’ state by interaction with the phosphorylated C‐terminus of photoactivated rhodopsin (R*), but the conformational changes in arrestin that lead to activation are unknown. Small‐angle X‐ray scattering (SAXS) was used to investigate the solution structure of arrestin and characterize changes attendant upon activation. Wild‐type arrestin forms dimers with a dissociation constant of 60 µ m . Small conformational changes, consistent with local movements of loops or the mobile N‐ or C‐termini of arrestin, were observed in the presence of a phosphopeptide corresponding to the C‐terminus of rhodopsin, and with an R175Q mutant. Because both the phosphopeptide and the R175Q mutation promote binding to unphosphorylated R*, we conclude that arrestin is activated by subtle conformational changes. Most of the arrestin will be in a dimeric state in vivo . Using the arrestin structure as a guide [Hirsch, J.A., Schubert, C., Gurevich, V.V. & Sigler, P.B. (1999) Cell 97 , 257–269], we have identified a model for the arrestin dimer that is consistent with our SAXS data. In this model, dimerization is mediated by the C‐terminal domain of arrestin, leaving the N‐terminal domains free for interaction with phosphorylated R*.