Light-activated rhodopsin induces structural binding motif in G protein α subunit

• DOI: 10.1073/pnas.95.8.4270
• Publication Date: 2002-07-26T14:40:11Z
• Authors: Oleg G. Kisselev; Jeff Kao; Jay W. Ponder; Yang C. Fann; N. Gautam; Garland R. Marshall
• Keywords: Transducin; Structural motif; Conformational change; Helix (gastropod)

A large superfamily of transmembrane receptors control cellular responses to diverse extracellular signals by catalyzing activation specific types heterotrimeric GTP-binding proteins. How these recognize and promote nucleotide exchange on G protein α subunits initiate signal amplification is unknown. The three-dimensional structure the transducin (Gt) subunit C-terminal undecapeptide Gtα(340–350) IKENLKDCGLF was determined transferred nuclear Overhauser effect spectroscopy while it bound photoexcited rhodopsin. Light rhodopsin causes a dramatic shift from disordered conformation binding motif with helical turn followed an open reverse centered at Gly-348, helix-terminating C capping L type. Docking NMR GDP-bound x-ray Gt reveals that promotes formation continuous helix over residues 325–346 terminated cap unique cluster crucial hydrophobic side chains. molecular mechanism which activated can proteins through reversible conformational changes receptor–G interface demonstrated.