Publication Abstract from PubMed
Visual signal transduction is a nearly noise-free process that is exquisitely well regulated over a wide dynamic range of light intensity. A key component in dark/light adaptation is phosducin, a phosphorylatable protein that modulates the amount of transducin heterotrimer (Gt alpha beta gamma) available through sequestration of the beta gamma subunits (Gt beta gamma). The structure of the phosphophosducin/Gt beta gamma complex combined with mutational and biophysical analysis provides a stereochemical mechanism for the regulation of the phosducin-Gt beta gamma interaction. Phosphorylation of serine 73 causes an order-to-disorder transition of a 20-residue stretch, including the phosphorylation site, by disrupting a helix-capping motif. This transition disrupts phosducin's interface with Gt beta gamma, leading to the release of unencumbered Gt beta gamma, which reassociates with the membrane and Gt alpha to form a signaling-competent Gt alpha beta gamma heterotrimer.
A molecular mechanism for the phosphorylation-dependent regulation of heterotrimeric G proteins by phosducin.,Gaudet R, Savage JR, McLaughlin JN, Willardson BM, Sigler PB Mol Cell. 1999 May;3(5):649-60. PMID:10360181[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
