Akiyoshi NakamuraMin YaoSarin ChimnaronkNaoki SakaiIsao TanakaHokkaido UniversityMahidol University2018-08-202018-08-202006-06-30Science. Vol.312, No.5782 (2006), 1954-195810959203003680752-s2.0-33745596803https://repository.li.mahidol.ac.th/handle/20.500.14594/23943The formation of glutaminyl transfer RNA (Gln-tRNAGln) differs among the three domains of life. Most bacteria employ an indirect pathway to produce Gln-tRNAGln by a heterotrimeric glutamine amidotransferase CAB (GatCAB) that acts on the misacylated Glu-tRNAGln. Here, we describe a series of crystal structures of intact GatCAB from Staphylococcus aureus in the apo form and in the complexes with glutamine, asparagine, Mn 2+, and adenosine triphosphate analog. Two identified catalytic centers for the glutaminase and transamidase reactions are markedly distant but connected by a hydrophilic ammonia channel 30 Å in length. Further, we show that the first U-A base pair in the acceptor stem and the D loop of tRNAGln serve as identity elements essential for discrimination by GatCAB and propose a complete model for the overall concerted reactions to synthesize Gln-tRNAGln.Mahidol UniversityMultidisciplinaryArticleSCOPUS10.1126/science.1127156