Type 1 glutamine amidotransferase (GATase1)-like domainType 1 glutamine amidotransferase (GATase1)-like domain. This group contains proteins similar to Class I glutamine amidotransferases, the intracellular PH1704 from Pyrococcus horikoshii, the C-terminal of the large catalase: Escherichia coli HP-II, Sinorhizobium meliloti Rm1021 ThuA, the A4 beta-galactosidase middle domain and peptidase E. The majority of proteins in this group have a reactive Cys found in the sharp turn between a beta strand and an alpha helix termed the nucleophile elbow. For Class I glutamine amidotransferases proteins which transfer ammonia from the amide side chain of glutamine to an acceptor substrate, this Cys forms a Cys-His-Glu catalytic triad in the active site. Glutamine amidotransferases activity can be found in a range of biosynthetic enzymes included in this cd: glutamine amidotransferase, formylglycinamide ribonucleotide, GMP synthetase, anthranilate synthase component II, glutamine-dependent carbamoyl phosphate synthase (CPSase), cytidine triphosphate synthetase, gamma-glutamyl hydrolase, imidazole glycerol phosphate synthase and, cobyric acid synthase. For Pyrococcus horikoshii PH1704, the Cys of the nucleophile elbow together with a different His and, a Glu from an adjacent monomer form a catalytic triad different from the typical GATase1 triad. Peptidase E is believed to be a serine peptidase having a Ser-His-Glu catalytic triad which differs from the Cys-His-Glu catalytic triad of typical GATase1 domains, by having a Ser in place of the reactive Cys at the nucleophile elbow. The E. coli HP-II C-terminal domain, S. meliloti Rm1021 ThuA and the A4 beta-galactosidase middle domain lack the catalytic triad typical GATaseI domains. GATase1-like domains can occur either as single polypeptides, as in Class I glutamine amidotransferases, or as domains in a much larger multifunctional synthase protein, such as CPSase. Peptidase E has a circular permutation in the common core of a typical GTAse1 domain.