Amino acids involved in conformational dynamics and G protein coupling of an odorant receptor: targeting gain-of-function mutation.
Thousands of different odorants are recognized and discriminated by odorant receptors (ORs) in the guanine nucleotide-binding protein (G protein)-coupled seven-transmembrane receptor family. Odorant-bound ORs stimulate Gs-type G proteins, Galphaolf, which in turn activates cAMP-mediated signaling pathway in olfactory sensory neurons. To better understand the molecular basis for OR activation and G protein coupling, we analyzed the effects of a series of site-directed mutations of mouse ORs, on function. Mutations of conserved amino acid residues in an intracellular loop or the C-terminus resulted in loss of activity without impairing ligand-binding activity, indicating that these residues are involved in Galphas/olf coupling. Moreover, mutation of the serine in KAFSTC, the OR-specific sequence motif, resulted in a dramatic increase in odorant responsiveness, suggesting that the motif is involved in a conformational change of the receptor that regulates G protein coupling efficiency. Our results provide insights into how ORs switch from an inactive to an active state, as well as where and how activated ORs interact with G proteins.
Kato
Aya
A
Department of Integrated Biosciences, The University of Tokyo, Chiba, Japan.
Katada
Sayako
S
Touhara
Kazushige
K
D000596:Amino Acids / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D005434:Flow Cytometry; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D016297:Mutagenesis, Site-Directed / Q000379:methods; D009154:Mutation; D017711:Nonlinear Dynamics; D017433:Protein Structure, Secondary; D018035:Receptors, Odorant / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014162:Transfection / Q000379:methods
D000596:Amino Acids; D018035:Receptors, Odorant; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D002118:Calcium