Agonist-specific conformational changes in the yeast alpha-factor pheromone receptor.

AUTOR(ES)

Büküşoğlu, G

RESUMO

The 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.

Documentos Relacionados

• Direct evidence for ligand-induced internalization of the yeast alpha-factor pheromone receptor.
• Saccharomyces cerevisiae mutants unresponsive to alpha-factor pheromone: alpha-factor binding and extragenic suppression.
• Elimination of defective alpha-factor pheromone receptors.
• Regulation of the G-protein-coupled alpha-factor pheromone receptor by phosphorylation.
• Structural determinants of agonist-specific kinetics at the ionotropic glutamate receptor 2