A constitutively active G-protein-coupled receptor causes mating self-compatibility in the mushroom Coprinus

In the mushroom Coprinus cinereus, the multiallelic B mating type genes are predicted to encode a large family of seven-transmembrane domain receptors and CaaX-modified pheromones. We have shown that a single amino acid chang e Q229P in transmembrane domain VI of one receptor confers a self-compatibl e mating phenotype, Using a heterologous yeast assay, we have demonstrated that this C.cinereus pheromone receptor is a G-protein-coupled receptor and that the Q229P mutation is constitutively activating. A C.cinereus pheromo ne precursor was processed to an active species specifically in yeast MATa cells and activated the co-expressed wild-type receptor. Yeast cells expres sing the wild-type receptor were used to test the activity of synthetic pep tides, enabling us to predict the structure of the mature C.cinereus pherom one and to show that the Q229P mutation does not compromise normal receptor function.