This family represents the shorter, B, chain of the homo-dimeric structure which is a guanine nucleotide-binding protein that binds and hydrolyses GTP. TrmE is homologous to the tetrahydrofolate-binding domain of N,N-dimethylglycine oxidase and indeed binds formyl-tetrahydrofolate. TrmE actively participates in the formylation reaction of uridine and regulates the ensuing hydrogenation reaction of a Schiff's base intermediate. This B chain is the N-terminal portion of the protein consisting of five beta-strands and three alpha helices and is necessary for mediating dimer formation within the protein [1].

1: The structure of the TrmE GTP-binding protein and its implications for tRNA modification. Scrima A, Vetter IR, Armengod ME, Wittinghofer A; EMBO J. 2005;24:23-33. PMID:15616586