Fig. 2.

Amino acid-induced TORC1 activation in yeast. Gtr1p and Gtr2p in yeast are orthologs of mammalian Rag A/B and Rag C/D GTPases, respectively. Gtr1p^GTP-Gtr2p^GDP forms an active heterodimer to mediate amino acid-induced TORC1 activation. Gtr1p^GTP-Gtr2p^GDP heterodimer interacts with Ltv1, Ego1, and Ego3, and forms an EGO/GSE complex, which is localized to the vacuole surface via N-terminal myristoylation of Ego1. Vam6 interacts with Gtr1p and functions as a GEF for Gtr1p. Cdc60, a leucine sensor, binds to Gtr1p^GDP and prevents GTP from hydrolysis, and therefore activates TORC1