SAM (sterile alpha motif) domain of Ste50 fungal subfamily is a protein-protein interaction domain. Proteins of this subfamily have SAM domain at the N-terminus and Ras-associated UBQ superfamily domain at the C-terminus. They participate in regulation of mating pheromone response, invasive growth and high osmolarity growth response, and contribute to cell wall integrity in vegetative cells. Ste50 of S.cerevisiae acts as an adaptor protein between G protein and MAP triple kinase Ste11. Ste50 proteins are able to form homooligomers, binding each other via their SAM domains, as well as heterodimers and heterogeneous complexes with SAM domain or SAM homodimers of MAPKKK Ste11 protein kinase.
Comment:The end-helix (EH) surface of SAM domain of Ste50 protein interacts with the mid-loop (ML) surface of SAM of Ste11 protein in head-to-tail manner (based on mutagenesis, NMR analysis and gel filtration experiments).
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