Menaquinone production in genetically engineered E. coli.

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Menaquinone (MK) is a crucial electron transporter in Escherichia coli, enabling survival in various conditions.
• Isoprenoid quinones with diverse side chain lengths are common in nature.
• Heterologous expression of polyprenyl diphosphate synthases (PDSs) has been explored for ubiquinone (UQ) production.

Purpose of the Study:

• To investigate menaquinone (MK) production in E. coli through the heterologous expression of various PDS genes.
• To compare the substrate specificity of prenyl transferases involved in MK and UQ biosynthesis.
• To identify genetic factors influencing MK production in E. coli.

Main Methods:

• Heterologous expression of prokaryotic and eukaryotic PDS genes (S. cerevisiae COQ1, H. influenzae hi0881, Synechocystis sp. slr0611, G. suboxydans ddsA) in E. coli.
• Detection and identification of specific MK isoforms using analytical techniques.
• Analysis of E. coli strains with mutations in menA and menC genes.

Main Results:

• Expression of HI0881, Slr0611, and DdsA led to the detection of MK7, MK9, and MK10, respectively.
• Expression of Coq1 resulted in minimal MK6 production, although UQ6 was detected, indicating narrower side chain acceptance by MenA compared to UbiA.
• Mutations in menA and menC were identified in specific E. coli strains.

Conclusions:

• The prenyl transferase MenA in the menaquinone pathway exhibits a more restricted substrate specificity for isoprenoid side chain lengths than UbiA in the ubiquinone pathway.
• Understanding these differences is key to engineering quinone production in E. coli.
• Genetic variations in menA and menC impact menaquinone biosynthesis.