Chromosomal location and cloning of the gene (trmD) responsible for the synthesis of tRNA (m1G) methyltransferase in Escherichia coli K-12

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Abstract
The trmD gene, which governs the formation of 1-methyl-guanosine (m1G) in transfer ribonucleic acid (tRNA), has been located by phage P1 transduction at 56 min on the chromosomal map of Escherichia coli. Cotransduction to tyrA at 56 min is 80%. From the Clarke and Carbon collection a ColE1-tyrA+ hybrid plasmid was isolated, which carried the trmD+ gene and was shown to over-produce the tRNA (m1G)methyltransferase. By subcloning restriction enzyme fragments in vitro, the trmD+ gene was located to a 3.4 kb DNA fragment 6.5 kb clockwise from the tyrA+ gene. The mutation trmD1, which renders the tRNA (m1G) methyltransferase temperaturesensitive both in vivo and in vitro could be complemented by trmD+ plasmids. These results suggest that the gene trmD+ is the structural gene for the tRNA (m1G)methyltransferase (EC 2.1.1.3.1).