Agonist-specific conformational changes in the yeast alpha-factor pheromone receptor
UMass Chan AffiliationsDepartment of Molecular Genetics and Microbiology
Graduate School of Biomedical Sciences
KeywordsAmino Acid Sequence; Fungal Proteins; GTP-Binding Proteins; Ligands; Molecular Sequence Data; Peptides; Protein Binding; *Protein Conformation; Receptors, Mating Factor; Receptors, Peptide; *Transcription Factors
Medicine and Health Sciences
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AbstractThe yeast alpha-factor pheromone receptor is a member of the G-protein-coupled receptor family. Limited trypsin digestion of yeast membranes was used to investigate ligand-induced conformational changes in this receptor. The agonist, alpha-factor, accelerated cleavage in the third intracellular loop, whereas the antagonist, desTrp1,Ala3-alpha-factor, reduced the cleavage rate. Thus, the enhanced accessibility of the third intracellular loop is specific to the agonist. alpha-Factor inhibited cleavage weakly at a second site near the cytoplasmic terminus of the seventh transmembrane helix, whereas the antagonist showed a stronger inhibition of cleavage at this site and at another site in the C-terminal domain of the receptor. The alpha-factor-induced conformational changes appeared to be inherent properties of the receptor, as they were retained in G-protein-deficient mutants. Moreover, a mutant receptor (ste2-L236H) that affects the third loop and is defective for G-protein coupling retained the ability to undergo the agonist-induced conformational changes. These results are consistent with a model in which G-protein activation is limited by the availability of specific contacts between the G protein and the third intracellular loop of the receptor. The antagonist appears to promote a distinct conformational state that differs from either the unoccupied or the agonist-occupied state.
Mol Cell Biol. 1996 Sep;16(9):4818-23.
Permanent Link to this Itemhttp://hdl.handle.net/20.500.14038/32958