Glutamyl tRNA Amidotransferase Subunit E (GATE)

GatB and GatE are paralogous subunits having a tRNA-dependent kinase activity, while GatA and GatD are the glutaminase subunits of the AdT. For transamidation of Glu on the tRNAs, Glu-AdT catalyzes three sequential reactions. First, the GatB (or GatE) subunit uses ATP to phosphorylate the Glu moiety on the Glu-tRNAGln, forming a γ-phosphoryl-Glu-tRNAGln as an activated intermediate. Second, the GatA (or GatD) subunit catalyzes the liberation of ammonia from Gln as an amide donor. Finally, Glu-AdT amidates the activated intermediate using the liberated ammonia to form Gln-tRNAGln. In Saccharomyces cerevisiae, it is known that gatA and gatB orthologs encoded in nuclear genome are involved in mitochondrial function, although gatC ortholog was not identified. These observations strongly indicated that Gln-tRNAGln is formed via the indirect pathway in yeast mitochondria.