Participates in the process of sexual differentiation and the determination of cell shape. Essential for mating and for recognition of the mating pheromone, but not for vegetative growth. Does not regulate the intracellular cAMP level. Regulates two downstream pathways, namely the byr2/byr1/spk1 mitogen-activated protein kinase cascade and the cdc42 small G protein pathway. The former is relevant to mating and sporulation, whereas the latter is relevant to mating, cell growth and cell morphology. GTP + H2O = GDP + H(+) + phosphate Alternates between an inactive form bound to GDP and an active form bound to GTP. Activated by a guanine nucleotide-exchange factor (GEF) and inactivated by a GTPase-activating protein (GAP). Scd1, scd2, cdc42, and ras1, in its GTP-bound state, act cooperatively to form a protein complex. Palmitoylated by the erf2-erf4 complex. Belongs to the small GTPase superfamily. Ras family.