National Center for
4O1E: Structure Of A Methyltransferase Component In Complex With Mthf Involved In O-demethylation
Structures of the methyltransferase component of Desulfitobacterium hafniense DCB-2 O-demethylase shed light on methyltetrahydrofolate formation
Acta Crystallogr. D Biol. Crystallogr. (2015) 71 p.1900-1908
O-Demethylation by acetogenic or organohalide-respiring bacteria leads to the formation of methyltetrahydrofolate from aromatic methyl ethers. O-Demethylases, which are cobalamin-dependent, three-component enzyme systems, catalyse methyl-group transfers from aromatic methyl ethers to tetrahydrofolate via methylcobalamin intermediates. In this study, crystal structures of the tetrahydrofolate-binding methyltransferase module from a Desulfitobacterium hafniense DCB-2 O-demethylase were determined both in complex with tetrahydrofolate and the product methyltetrahydrofolate. While these structures are similar to previously determined methyltransferase structures, the position of key active-site residues is subtly altered. A strictly conserved Asn is displaced to establish a putative proton-transfer network between the substrate N5 and solvent. It is proposed that this supports the efficient catalysis of methyltetrahydrofolate formation, which is necessary for efficient O-demethylation.