This family of proteins includes the known homologues STD1 (also known as MSN3) and MTH1. Both STD1 and MTH1 are involved in modulating the expression of glucose-regulated genes in yeast, but have been shown to function by slightly different methods. It has been suggested that both STD1 and MTH1 are required to repress the hexose transporter genes in low glucose conditions [1]. STD1 has also been shown to stimulate SNF1 kinase through interaction with the catalytic domain of SNF1, antagonising auto-inhibition and promoting an active conformation of the kinase [2].

1: Std1 and Mth1 proteins interact with the glucose sensors to control glucose-regulated gene expression in Saccharomyces cerevisiae. Schmidt MC, McCartney RR, Zhang X, Tillman TS, Solimeo H, Wolfl S, Almonte C, Watkins SC; Mol Cell Biol. 1999;19:4561-4571. PMID:10373505

2: Std1p (Msn3p) positively regulates the Snf1 kinase in Saccharomyces cerevisiae. Kuchin S, Vyas VK, Kanter E, Hong SP, Carlson M; Genetics. 2003;163:507-514. PMID:12618390