Table 3.

Transamidase activity of the M. thermautotrophicus (M.t.) GatCAB and GatDE, and the H. pylori (H.p.) GatCAB with different mischarged tRNA substrates ^*

	Transamidase activity (ktrans, s−1)
aa-tRNAa	M.t. GatCABb	M.t. GatDEc	H.p. GatCABd
M.t. GlutRNAGln	NDe	0.98 ± 0.27	0.08 ± 0.02
H.p. Glu-tRNAGln	0.08 ± 0.02	0.01 ± <0.01	3.12 ± 0.09
B.s. Glu-tRNAGln	0.004 ± 0.003	0.01 ± <0.01	2.2 ± 0.1
C.t. Asp-tRNAAsn	0.09 ± 0.01	NDe	1.27 ± 0.01
M.t. Asp-tRNAAsn	0.11 ± 0.01	NDe	0.01 ± <0.01

^*Measurements were from three to four separate experiments. Standard deviations are reported. Reactions were carried out at 37 °C in the presence of ATP (4 mM), amide donor (4 mM), and aa-tRNA (10 µM) indicated. For reactions with the GatCAB enzymes, Gln was provided as the amide donor. In reactions with GatDE, Asn was the donor.

^aThe aa-tRNA substrates tested were the M. thermautotrophicus (M.t.), H. pylori (H.p.), and B. subtilis (B.s.) Glu-tRNA^Gln, and the C. trachomatis (C.t.) and M. thermautotrophicus (M.t.) Asp-tRNA^Asn.

^bIn reactions with M.t. GatCAB, enzyme concentrations ranged from 20 nM to 1 µM.

^cIn reactions with M.t. GatDE, enzyme concentrations ranged from 20 nM to 1 µM.

^dIn reactions with H.p. GatCAB, enzyme concentrations ranged from 10 nM to 100 nM.

^eND stands for no-detectable activity under conditions assayed.