Abstract of the PDB Structure's related Publication:
Methylaminomethyl modification of uridine or 2-thiouridine (mnm5U34 or mnm5s2U34) at the wobble position of tRNAs specific for glutamate, lysine and arginine are observed in Escherichia coli and allow for specific recognition of codons ending in A or G. In the biosynthetic pathway responsible for this post-transcriptional modification, the bifunctional enzyme MnmC catalyzes the conversion of its hypermodified substrate carboxymethylaminomethyl uridine (cmnm5U34) to mnm5U34. MnmC catalyzes the flavin adenine dinucleotide (FAD)-dependent oxidative cleavage of carboxymethyl group from cmnm5U34 via an imine intermediate to generate aminomethyl uridine (nm5U34), which is subsequently methylated by S-adenosyl-L-methionine (SAM) to yield methylaminomethyl uridine (mnm5U34).
Homologue of E. coli MnmCD. In E.coli (and many other bacteria) it is a bifunctional enzyme, composed of two domains that catalyze two successive reactions at the uridine wobble position 34 in tRNA: first a deacetylation reaction of cmnm5U into nm5U, then methylation of the amine group of nm5U to form mnm5U. In other organisms they may be unlinked (separate proteins), then identified as MnmC for the deacetylase and MnmD for the methylase. In certain bacteria, the catalytic domain for the deacetylation reaction is absent in their genome and only the gene coding for MnmD is present. In other bacteria, MnmC and MnmD are both present.