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

Summary 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).