High-affinity low glucose sensor that is part of the sensor/receptor-repressor (SSR) glucose-signaling pathway, which detects extracellular glucose and induces expression of glucose transporters that bring glucose into the cell (PubMed:8901598, PubMed:9564039). The transporter-like sensor generates an intracellular signal in the presence of low levels of glucose to promote low glucose-induced expression of HXT2 (PubMed:9564039). Binding of glucose to the SNF3 transmembrane domain activates a downstream signaling cascade, leading to phosphorylation of the RGT1 corepressors MTH1 and STD1, targeting them for SCF(Grr1)-dependent ubiquitination and degradation. Depletion of the corepressors robs RGT1 of its ability to repress expression of HXT genes, leading to accumulation of glucose transporters in the plasma membrane (By similarity). SNF3 is involved as well in the transport of mannose and fructose (PubMed:20014043). Even though SNF3 is similar to glucose transporters, it appears to be unable to transport glucose (PubMed:9564039). Glucose-repressible. The C-terminal cytoplasmic domain seems to be important for SNF3 regulatory function. Phosphorylated in the C-terminal tail on Yck consensus sites in a yeast casein kinases YCK1 and YCK2 (Yck)-dependent manner. This phosphorylation is required for interaction with HXT corepressors MTH1 and STD1 and ultimately HXT expression. Belongs to the major facilitator superfamily. Sugar transporter (TC 2.A.1.1) family.