Crystal structure of methionyl-tRNA(f)(Met) transformylase complexed with the initiator formylmethionyl-tRNA(f)(Met)

The crystal structure of Escherichia coli methionyl-tRNA(f)(Met) transformy lase complexed with formyl-methionyI-tRNA(f)(Met) was solved at 2.8 Angstro m resolution. The formylation reaction catalyzed by this enzyme irreversibl y commits methionyl-tRNA(f)(Met) to initiation of translation in eubacteria . In the three-dimensional model, the methionyl-tRNA(f)(Met) formyltransfer ase fills in the inside of the L-shaped tRNA molecule on the D-stem side. T he anticodon stem and loop are away from the protein. An enzyme loop is wed ged in the major groove of the acceptor helix. As a result, the C1-A72 mism atch characteristic of the initiator tRNA is split and the 3' arm bends ins ide the active centre. This recognition mechanism is markedly distinct from that of elongation factor Tu, which binds the acceptor arm of aminoacylate d elongator tRNAs on the T-stem side.