Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5914613 | Journal of Structural Biology | 2011 | 8 Pages |
The process of vision is initiated when the G protein-coupled receptor, rhodopsin (Rho), absorbs a photon and transitions to its activated Rhoâ form. Rhoâ binds the heterotrimeric G protein, transducin (Gt) inducing GDP to GTP exchange and Gt dissociation. Using nucleotide depletion and affinity chromatography, we trapped and purified the resulting nucleotide-free Rhoâ·Gt complex. Quantitative SDS-PAGE suggested a 2:1 molar ratio of Rhoâ to Gt in the complex and its mass determined by scanning transmission electron microscopy was 221 ± 12 kDa. A 21.6 à structure was calculated from projections of negatively stained Rhoâ·Gt complexes. The molecular envelope thus determined accommodated two Rho molecules together with one Gt heterotrimer, corroborating the heteropentameric structure of the Rhoâ·Gt complex.