Activation of rhodopsin: new insights from structural and biochemical studies.
G-protein-coupled receptors (GPCRs) are involved in a vast variety of cellular signal transduction processes from visual, taste and odor perceptions to sensing the levels of many hormones and neurotransmitters. As a result of agonist-induced conformation changes, GPCRs become activated and catalyze nucleotide exchange within the G proteins, thus detecting and amplifying the signal. GPCRs share a common heptahelical transmembrane structure as well as many conserved key residues and regions. Rhodopsins are prototypical GPCRs that detect photons in retinal photoreceptor cells and trigger a phototransduction cascade that culminates in neuronal signaling. Biophysical and biochemical studies of rhodopsin activation, and the recent crystal structure determination of bovine rhodopsin, have provided new information that enables a more complete mechanism of vertebrate rhodopsin activation to be proposed. In many aspects, rhodopsin might provide a structural and functional template for other members of the GPCR family.
Okada
T
T
Dept of Ophthalmology, University of Washington, Seattle, WA 98195, USA.
Ernst
O P
OP
Palczewski
K
K
Hofmann
K P
KP
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D003593:Cytoplasm / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017785:Photons; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism; D012164:Retinal Diseases / Q000378:metabolism; D012243:Rhodopsin / Q000737:chemistry* / Q000378:metabolism*; D015398:Signal Transduction
D020662:Guanine Nucleotide Exchange Factors; D011956:Receptors, Cell Surface; D012243:Rhodopsin; D019204:GTP-Binding Proteins