Visual arrestin activity may be regulated by self-association.

Schubert C, Hirsch JA, Gurevich VV, Engelman DM, Sigler PB, Fleming KG
J Biol Chem. 1999 274 (30): 21186-90

PMID: 10409673 · DOI:10.1074/jbc.274.30.21186

Visual arrestin is the protein responsible for rapid quenching of G-protein-coupled receptor signaling. Arrestin exists as a latent inhibitor which must be 'activated' upon contact with a phosphorylated receptor. X-ray crystal structures of visual arrestin exhibit a tetrameric arrangement wherein an asymmetric dimer with an extensive interface between conformationally different subunits is related to a second asymmetric dimer by a local two-fold rotation axis. To test the biological relevance of this molecular organization in solution, we carried out a sedimentation equilibrium analysis of arrestin at both crystallographic and physiological protein concentrations. While the tetrameric form can exist at the high concentrations used in crystallography experiments, we find that arrestin participates in a monomer/dimer equilibrium at concentrations more likely to be physiologically relevant. Solution interaction analysis of a proteolytically modified, constitutively active form of arrestin shows diminished dimerization. We propose that self-association of arrestin may provide a mechanism for regulation of arrestin activity by (i) ensuring an adequate supply for rapid quenching of the visual signal and (ii) limiting the availability of active monomeric species, thereby preventing inappropriate signal termination.

MeSH Terms (11)

Animals Arrestin Crystallography, X-Ray Escherichia coli Eye Proteins GTP-Binding Proteins Protein Conformation Recombinant Proteins Signal Transduction Structure-Activity Relationship Visual Perception

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