<p>In <taxon tax_id="562">Escherichia coli</taxon>, the protein previously designated YfcK is now identified as the bifunctional enzyme MnmC. It acts, following the action of the heterotetramer of GidA and MnmE, in the modification of U-34 of certain tRNA to 5-methylaminomethyl-2-thiouridine (mnm5s2U). In other bacteria, the corresponding proteins are usually but always found as a single polypeptide chain, but occasionally as the product of tandem genes. This entry represents the C-terminal region of the multifunctional protein.</p>