Two dedicated class C radical S-adenosylmethionine methyltransferases concertedly catalyse the synthesis of 7,8-dimethylmenaquinone

Biochim Biophys Acta Bioenerg. 2018 Apr;1859(4):300-308. doi: 10.1016/j.bbabio.2018.01.010. Epub 2018 Feb 3.


Dimethylmenaquinone (DMMK), a prevalent menaquinone (MK) derivative of uncertain function, is characteristic for members of the class Coriobacteriia. Such bacteria are frequently present in intestinal microbiomes and comprise several pathogenic species. The coriobacterial model organism Adlercreutzia equolifaciens was used to investigate the enzymology of DMMK biosynthesis. A HemN-like class C radical S-adenosylmethionine methyltransferase (MenK2) from A. equolifaciens was produced in Wolinella succinogenes or Escherichia coli cells and found to methylate MK specifically at position C-7. In combination with a previously described MK methyltransferase (MqnK/MenK) dedicated to MK methylation at C-8, 7,8-DMMK6 was produced in W. succinogenes. The position of the two methyl groups was confirmed by two-dimensional NMR and midpoint redox potentials of 7-MMK6, 8-MMK6 and 7,8-DMMK6 were determined by cyclic voltammetry. A phylogenetic tree of MenK, MenK2 and HemN proteins revealed a Coriobacteriia-specific MenK2 clade. Using chimeric A. equolifaciens MenK/MenK2 proteins produced in E. coli it was shown that the combined linker and HemN domains determined the site-specificity of methylation. The results suggest that the use of MenK2 as a biomarker allows predicting the ability of DMMK synthesis in microbial species.

Keywords: Coriobacteriia; Dimethylmenaquinone; Menaquinone; Methylmenaquinone; Radical SAM methyltransferase; Redox potential.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinobacteria / classification
  • Actinobacteria / enzymology*
  • Actinobacteria / genetics
  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Biocatalysis
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Gene Expression
  • Genetic Vectors / chemistry
  • Genetic Vectors / metabolism
  • Isoenzymes / chemistry
  • Isoenzymes / classification
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Kinetics
  • Oxidation-Reduction
  • Phylogeny
  • Protein Binding
  • Protein O-Methyltransferase / chemistry*
  • Protein O-Methyltransferase / classification
  • Protein O-Methyltransferase / genetics
  • Protein O-Methyltransferase / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • S-Adenosylmethionine / chemistry*
  • S-Adenosylmethionine / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Vitamin K 2 / metabolism*
  • Wolinella / classification
  • Wolinella / enzymology*
  • Wolinella / genetics


  • Bacterial Proteins
  • Isoenzymes
  • Recombinant Proteins
  • Vitamin K 2
  • S-Adenosylmethionine
  • Protein O-Methyltransferase