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Biosynthesis and function of microbial methylmenaquinones.

Dennis Wilkens1, Jörg Simon2

  • 1Microbial Energy Conversion and Biotechnology, Department of Biology, Technical University of Darmstadt, Schnittspahnstraße 10, Darmstadt, Germany.

Advances in Microbial Physiology
|July 28, 2023
PubMed
Summary
This summary is machine-generated.

Methylmenaquinones (MMKs), essential redox mediators, are synthesized by specific enzymes like MqnK, MenK, and MenK2. This study identifies key motifs for these menaquinone methyltransferases, aiding in predicting microbial quinone pools from genomes.

Keywords:
Anaerobic respirationClass C radical SAM methyltransferaseMen and futalosine (Mqn) pathwaysMenaquinone (MK)Menaquinone methyltransferases MqnK, MenK and MenK2Methylmenaquinone (MMK)Quinone/quinol poolWolinella succinogenes

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Area of Science:

  • Microbiology
  • Biochemistry
  • Genomics

Background:

  • Membranous quinones, particularly menaquinone (MK), are vital for cellular respiration and microbial taxonomy.
  • Methylated menaquinones (MMKs) are found across diverse microbial phyla and are implicated in anaerobic respiration due to their low redox potentials.

Purpose of the Study:

  • To characterize the menaquinone methyltransferases (MqnK, MenK, MenK2) responsible for synthesizing MMKs.
  • To identify sequence motifs for discriminating MK/MMK methyltransferases and C-7 specific enzymes.
  • To enable prediction of microbial quinone pool composition from genomic data.

Main Methods:

  • Functional expression of MqnK, MenK, and MenK2 in Escherichia coli.
  • Biochemical characterization of methylation reactions at C-7 and C-8 positions.
  • Bioinformatic analysis including cluster and phylogenetic analyses of methyltransferase sequences.

Main Results:

  • MqnK, MenK, and MenK2 catalyze the synthesis of 8-methylmenaquinone (8-MMK), 7-MMK, and 7,8-dimethylmenaquinone (DMMK).
  • Signature motifs were identified to distinguish MenK/MqnK/MenK2 enzymes from other radical SAM enzymes.
  • The MenK2 subfamily was identified as C-7 specific menaquinone methyltransferases.

Conclusions:

  • The characterized enzymes and identified motifs provide a foundation for engineering quinone pools.
  • This knowledge facilitates the prediction of menaquinone/menaquinol methylation status in microbial species and communities directly from their genomes.