Dominant-negative mutants of a yeast G-protein beta subunit identify two functional regions involved in pheromone signalling.

Abstract

The STE4 gene, which encodes the β subunit of the mating response G-protein in the yeast Saccharomyces cerevisiae, was subjected to a saturation mutagenesis using 'doped' oligodeoxynucleotides. We employed a genetic screen to select dominant-negative STE4 mutants, which when overexpressed from the GAL1 promoter, interfered with the signalling function of the wild type protein. The identified inhibitory amino acid alterations define two small regions that are crucially involved in transmitting the mating signal from Gβ to downstream components of the signalling pathway. These results underline the positive signalling role of yeast Gβ and assign for the first time the positive signalling function of a G-protein β subunit to specific structural features.