Recognition mechanism of tRNA with tRNA(guanosine-2')methyltransferase from Thermus thermophilus HB 27.

rRNA(Gm)methyltransferase from an extreme thermophile, Thermus thermophilus HB 27 specifically methylates the 2'-OH of the ribose ring of G18 in the invariant G18-G19 sequence in the D loop of tRNA. The interaction site on tRNA was presumed to be the D loop and stem structure. Destruction of tertiary structure of tRNA caused by heat resulted in a great decrease in the acceptor activity of methyl group. It was suggested by CD measurement that a conformational change of tRNA occurs when it forms an equimolar complex with Gm-methylase.