9.B.45. The Fungal Mating-type Pheromone Receptor (MAT-PR) Family 

The MAT-PR family consists of proteins with 7 TMSs and is considered to comprise Class D GPCR receptors (Shalaeva et al. 2015). 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).  These two subfamilies within the MMAT-PR Family are very distantly related, but both are distantly related to other GPCRs in TC Family 9.A.14.  They are therefore members of the TOG superfamily (Yee et al. 2013).