2.A.1.1.19
Glucose transporter and low affinity sensor, Rgt2p (regulates glucose transport in conjunction with Snf3p). Rgt2 generates an intracellular signal in response to glucose that leads to inhibition of the Rgt1 transcriptional repressor and consequently to derepression of HXT genes encoding glucose transporters. They have unusually long C-terminal tails that bind to Mth1 and Std1, paralogous proteins that regulate the function of the Rgt1 transcription factor. Scharff-Poulsen et al. 2018 showed that the C-terminal tail of Rgt2 is not responsible for its inability to transport glucose. RGT2 mutations that cause constitutive signal generation alter evolutionarily-conserved amino acids in the transmembrane spanning regions involved in maintaining an outward-facing conformation or the substrate binding site. These mutations may cause Rgt2 to adopt inward-facing or occluded conformations that generate the glucose signal. The cytoplasmic C-terminal domains of the yeast cell surface receptors Rgt2 and Snf3 play multiple roles in glucose sensing and signaling (Kim et al. 2024).