Structure of a TrmA-RNA complex: A consensus RNA fold contributes to substrate selectivity and catalysis in m5U methyltransferases.

ABSTRACT: TrmA catalyzes S-adenosylmethionine (AdoMet)-dependent methylation of U54 in most tRNAs. We solved the structure of the Escherichia coli 5-methyluridine (m(5)U) 54 tRNA methyltransferase (MTase) TrmA in a covalent complex with a 19-nt T arm analog to 2.4-A resolution. Mutation of the TrmA catalytic base Glu-358 to Gln arrested catalysis and allowed isolation of the covalent TrmA-RNA complex for crystallization. The protein-RNA interface includes 6 nt of the T loop and two proximal base pairs of the stem. U54 is flipped out of the loop into the active site. A58 occupies the space of the everted U54 and is part of a collinear base stack G53-A58-G57-C56-U55. The RNA fold is different from T loop conformations in unbound tRNA or T arm analogs, but nearly identical to the fold of the RNA loop b

SUBMITTER: Alian A 

PROVIDER: S-EPMC2383949 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature