Figure 10. Amino Acid Substitutions in Mutants of the Yeast G-αq Protein Gpa1.

A theoretical three-dimensional structure of the yeast Gpa1 G-α protein in complex with the Ste4 protein (G-β) is shown. The position of four amino acid substitutions with phenotypes of interest is indicated by circles. Two alpha helices are indicated by yellow highlighting of the protein backbone. In higher eukaryotes, these helices are considered to form the interface with G-αq downstream effector proteins. Three mutations affecting adaptation to mating pheromone lie on this face: E355K and E364K both hyper-adapt while the M362I allele described in this work is hypo-adaptive. For reference, the position of a mutation affecting sensitivity to RGS GAP activity, G302S, is also shown.