Primary Citation of Related Structures: 1B9X, 1B9Y
PubMed Abstract:
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) ...
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.
Related Citations:
Crystal structure of a G-protein beta gamma dimer at 2.1A resolution. Sondek, J., Bohm, A., Lambright, D.G., Hamm, H.E., Sigler, P.B. (1996) Nature 379: 369
Crystal structure at 2.4 angstroms resolution of the complex of transducin betagamma and its regulator, phosducin. Gaudet, R., Bohm, A., Sigler, P.B. (1996) Cell 87: 577
Organizational Affiliation:
Department of Molecular Biophysics, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06511, USA.
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