Mating type proteins are sequence specific DNA-binding proteins that act as master switches in yeast differentiation by controlling gene expression in a cell type-specific fashion. Transcriptional activator that induces the transcription of alpha-specific genes (By similarity). There are three genetic loci for mating type genes in K.delphensis. MAT is the expression locus that determines the mating type of the cell, whereas HML (containing HMLALPHA1 and HMLALPHA2) and HMR (containing HMRA1) represent silenced repositories of mating type information. The mating type is determined by the MAT locus, which contains either a copy of HML or of HMR. Diploid cells are usually heterozygous for the MAT locus. Belongs to the MATALPHA1 family.