GTPase involved in activation of the TORC1 signaling pathway, which promotes growth and represses autophagy in nutrient-rich conditions (PubMed:28993463). Also required for TORC1 inactivation during nitrogen starvation (PubMed:28993463). Required for intracellular sorting of GAP1 out of the endosome (By similarity). Functionally associated with the inorganic phosphate transporter PHO84, and may be involved in regulating its function or localization (By similarity). Heterodimer; with GTR2 (By similarity). Component of the GSE complex composed of GTR1, GTR2, SLM4, MEH1 and LTV1 (By similarity). Interacts with GTR2; the interaction is direct (By similarity). Interacts with TOR1 (By similarity). Sensitive to rapamycin (TORC1 signaling-inhibitor) (PubMed:28993463). Simultaneous disruption of GTR2 results in abnormal localization of TOR1 and PIB2 to vacuoles and abnormal activation of TORC1 in nitrogen-replete conditions (glutamine or leucine nitrogen source) (PubMed:28993463). Belongs to the GTR/RAG GTP-binding protein family.