Structural highlights
Function
[ACSE_MOOTH] Methyltransferase that mediates the transfer of a N5-methyl group of (6S)-methyltetrahydrofolate to the 5-methoxybenzimidazolylcobamide cofactor of a corrinoid/Fe-S protein in the anaerobic acetyl-CoA pathway (Wood-Ljungdahl pathway) of carbon monoxide and carbon dioxide fixation.[1] [2] [3]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
BACKGROUND: Methyltetrahydrofolate, corrinoid iron-sulfur protein methyltransferase (MeTr), catalyzes a key step in the Wood-Ljungdahl pathway of carbon dioxide fixation. It transfers the N5-methyl group from methyltetrahydrofolate (CH3-H4folate) to a cob(I)amide center in another protein, the corrinoid iron-sulfur protein. MeTr is a member of a family of proteins that includes methionine synthase and methanogenic enzymes that activate the methyl group of methyltetra-hydromethano(or -sarcino)pterin. We report the first structure of a protein in this family. RESULTS: We determined the crystal structure of MeTr from Clostridium thermoaceticum at 2.2 A resolution using multiwavelength anomalous diffraction methods. The overall architecture presents a new functional class of the versatile triose phosphate isomerase (TIM) barrel fold. The MeTr tertiary structure is surprisingly similar to the crystal structures of dihydropteroate synthetases despite sharing less than 20% sequence identity. This homology permitted the methyl-H4folate binding site to be modeled. The model suggests extensive conservation of the pterin ring binding residues in the polar active sites of the methyltransferases and dihydropteroate synthetases. The most significant structural difference between these enzymes is in a loop structure above the active site. It is quite open in MeTr, where it can be modeled as the cobalamin binding site. CONCLUSIONS: The MeTr structure consists of a TIM barrel that embeds methyl-H4folate and cobamide. All related methyltransferases are predicted to fold into a similar TIM barrel pattern and have a similar pterin and cobamide binding site. The observed structure is consistent with either a 'front' (N5) or 'back' (C8a) side protonation of CH3-H4folate, a key step that enhances the electrophilic character of the methyl group, activating it for nucleophilic attack by Co(I).
Crystal structure of a methyltetrahydrofolate- and corrinoid-dependent methyltransferase.,Doukov T, Seravalli J, Stezowski JJ, Ragsdale SW Structure. 2000 Aug 15;8(8):817-30. PMID:10997901[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Doukov TI, Hemmi H, Drennan CL, Ragsdale SW. Structural and kinetic evidence for an extended hydrogen-bonding network in catalysis of methyl group transfer. Role of an active site asparagine residue in activation of methyl transfer by methyltransferases. J Biol Chem. 2007 Mar 2;282(9):6609-18. Epub 2006 Dec 15. PMID:17172470 doi:http://dx.doi.org/10.1074/jbc.M609828200
- ↑ Kung Y, Ando N, Doukov TI, Blasiak LC, Bender G, Seravalli J, Ragsdale SW, Drennan CL. Visualizing molecular juggling within a B(12)-dependent methyltransferase complex. Nature. 2012 Mar 14. doi: 10.1038/nature10916. PMID:22419154 doi:10.1038/nature10916
- ↑ Roberts DL, Zhao S, Doukov T, Ragsdale SW. The reductive acetyl coenzyme A pathway: sequence and heterologous expression of active methyltetrahydrofolate:corrinoid/iron-sulfur protein methyltransferase from Clostridium thermoaceticum. J Bacteriol. 1994 Oct;176(19):6127-30. PMID:7928975
- ↑ Doukov T, Seravalli J, Stezowski JJ, Ragsdale SW. Crystal structure of a methyltetrahydrofolate- and corrinoid-dependent methyltransferase. Structure. 2000 Aug 15;8(8):817-30. PMID:10997901
