Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. Plays a role in pathogenicity, specifically in appressorium formation in rice blast disease. Also involved in mating. G proteins are composed of 3 units; alpha, beta and gamma. The alpha chain contains the guanine nucleotide binding site. Belongs to the G-alpha family. G(q) subfamily.