Structures of the methyltransferase component of Desulfitobacterium hafniense DCB-2 O-demethylase shed light on methyltetrahydrofolate formation.
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.
Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, England.
Hanno
H
Sjuts
Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, England.
Mark S
MS
Dunstan
Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, England.
Karl
K
Fisher
Manchester Institute of Biotechnology, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, England.
David
D
Leys
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D045858:Desulfitobacterium / Q000201:enzymology*; D008780:Methyltransferases / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013763:Tetrahydrofolates / Q000138:chemical synthesis*
D013763:Tetrahydrofolates; C030371:5,6,7,8-tetrahydrofolic acid; D008780:Methyltransferases
O-demethylation; crystal structure; methyltetrahydrofolate; methyltransferase