Synthetic mycolates derivatives to decipher protein mycoloylation, a unique post-translational modification in...

Area of Science:

• Microbiology
• Biochemistry
• Structural Biology

Background:

• Protein mycoloylation is a unique post-translational modification (PTM) found in Corynebacteriales, impacting bacterial envelope structure.
• The mycomembrane, composed of mycolic acids, is a defining feature of these bacteria, including human pathogens.
• PorA is a mycomembrane protein recently identified as being covalently modified by mycolic acids.

Purpose of the Study:

• To identify the specific mycoloyltransferase responsible for protein mycoloylation.
• To elucidate the substrate specificity and mechanism of the mycoloylation process.
• To determine the structural basis of mycoloyltransferase activity.

Main Methods:

• Synthesis of trehalose monomycolate (TMM) analogs and trehalose dimycolate (TDM).
• Biochemical assays to assess MytC activity and substrate specificity.
• X-ray crystallography to determine the structure of MytC in complex with a mycolic acid moiety.

Main Results:

• MytC was confirmed as the mycoloyltransferase catalyzing protein mycoloylation.
• Trehalose monomycolate (TMM) was identified as the specific mycolate donor for PorA mycoloylation.
• The structure of MytC revealed conformational flexibility in its active site during the reaction cycle, showing covalent linkage to a mycolic acid.

Conclusions:

• MytC plays a crucial role in protein mycoloylation, a novel PTM involving mycolic acids.
• Understanding MytC's mechanism provides insights into the broader family of mycoloyltransferases, including essential enzymes in Mycobacteria.
• The findings open avenues for further research into bacterial envelope biogenesis and potential therapeutic targets.