6sk4
Methyltransferase MtgA from Desulfitobacterium hafniense in complex with methyl-tetrahydrofolate (P21)
Structural highlights
FunctionMTGA_DESHY Methyltransferase able to catalyze the transfer of a methyl group from methylcobalamin (methylCbl) to tetrahydrofolate (THF) in vitro, to generate methyl-THF and cob(I)alamin. In vivo, the methyl group probably comes from the adjacently encoded methylated corrinoid protein DSY3155. The methyl group may then be ultimately converted to carbon dioxide, and its oxidation would also provide reducing equivalents for anaerobic respiration. Thus, may function in the pathway that allows anaerobic methylotrophic growth of D.hafniense using glycine betaine.[1] Publication Abstract from PubMedEnzymes orchestrating methylation between tetrahydrofolate (THF) and cobalamin (Cbl) are abundant among all domains of life. During energy production in Desulfitobacterium hafniense, MtgA catalyzes the methyl transfer from methylcobalamin (Cbl-CH3 ) to THF in the catabolism of glycine betaine (GB). Despite its lack of sequence identity with known structures, we could show that MtgA forms a homodimeric complex of two TIM barrels. Atomic crystallographic insights into the interplay of MtgA with THF as well as analysis of a trapped reaction intermediate (THF-CH3 )(+) reveal conformational rearrangements during the transfer reaction. Whereas residues for THF methylation are conserved, the binding mode for the THF glutamyl-p-aminobenzoate moiety (THF tail) is unique. Apart from snapshots of individual reaction steps of MtgA, structure-based mutagenesis combined with enzymatic activity assays allowed a mechanistic description of the methyl transfer between Cbl-CH3 and THF. Altogether, the THF-tail-binding motion observed in MtgA is unique compared to other THF methyltransferases and therefore contributes to the general understanding of THF-mediated methyl transfer. Structures in Tetrahydrofolate Methylation in Desulfitobacterial Glycine Betaine Metabolism at Atomic Resolution.,Badmann T, Groll M Chembiochem. 2019 Sep 13. doi: 10.1002/cbic.201900515. PMID:31518049[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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