Mating-type pheromone α-receptor of 431 aas and 7 TMSs, STE2 (Nakayama et al. 1987).  The G protein-coupled receptors Ste2 and Ste3 bind α- and a-factor, respectively, in Saccharomyces cerevisiae. These receptors share a similar conformation, with seven transmembrane segments, three intracellular loops, a C-terminal tail, and three extracellular loops. However, the amino acid sequences of these two receptors bear little resemblance to each other, and the two ligands, α-factor and a-factor, have different sequences although both receptors activate the same G protein (Gastaldi et al. 2016).