Crystallization and preliminary X-ray crystallographic characterization of TrmFO, a folate-dependent tRNA methyltransferase from Thermotoga maritima

TrmFO, previously classified as GID, is a methyltransferase that catalyzes the formation of 5-methyluridine or ribothymidine (T) at position 54 in tRNA in some Gram-positive bacteria. To date, TrmFO is the only characterized tRNA methyltransferase that does not use S-adenosylmethionine as the methyl-group donor. Instead, the donor of the methyl group is N-5, N-10-methylenetetrahydrofolate. The crystallization and preliminary X-ray crystallographic studies of TrmFO are reported here. The recombinant protein, cloned from Thermotoga maritima genomic DNA, was overproduced in Esherichia coli and crystallized in 25%(v/v) PEG 4000, 100 mM NaCl and sodium citrate buffer pH 5.0 at 291 K using the hanging-drop vapor-diffusion method. The plate-shaped crystals diffracted to 2.6 angstrom and belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 79.94, b = 92.46, c = 127.20 angstrom.