FIGURE 2.

Amino acid availability regulates cell growth at least in part through tRNA-related activities

Leu-tRNA (LRS) synthase forms a ternary complex with leucine and acts as a GAP for Rag-GTPases to promote TORC1 activity and, therefore, efficient protein translation and cell growth under nutrient-rich conditions. Note that tRNA binding may not be required for the activation of TORC1 by LRS (see text for details). During starvation, uncharged tRNAs accumulate, bind, and activate the protein kinase Gcn2 to reduce translation efficiency and cell growth.