GLU-TRNA(GLN) AMIDOTRANSFERASE - A NOVEL HETEROTRIMERIC ENZYME REQUIRED FOR CORRECT DECODING OF GLUTAMINE CODONS DURING TRANSLATION

The three genes, gatC, gatA, and gatB, which constitute the transcript ional unit of the Bacillus subtilis glutamyl-tRNA(Gln) amidotransferas e have been cloned, Expression of this transcriptional unit results in the production of a heterotrimeric protein that has been purified to homogeneity, The enzyme furnishes a means for formation of correctly c harged Gln-tRNA(Gln) through the transamidation of misacylated Glu-tRN A(Gln), functionally replacing the lack of glutaminyl-tRNA synthetase activity in Gram-positive eubacteria, cyanobacteria, Archaea, and orga nelles. Disruption of this operon is lethal, This demonstrates that tr ansamidation is the only pathway to Gln-tRNA(Gln) in B. subtilis and t hat glutamyl-tRNA(Gln) amidotransferase is a novel and essential compo nent of the translational apparatus.