PptT in the spotlight: deciphering the mechanism of action of an essential enzyme from Mycobacterium tuberculosis

PptT, a 4′-phosphopantetheinyl transferase from Mycobacterium tuberculosis, is an essential enzyme involved in the synthesis of complex mycobacterial lipids that contribute to the virulence and pathogenicity of the bacillus. In an recently published article in ACS Catalysis, researchers have deciphered the mechanism by which PptT activates megasynthases involved in the production of these lipids. The results of this research enhance our understanding of PKS modification and represent significant progress in the development of anti-TB drugs.

Figure: Schematic representation of the activation cycle of PptT from Mycobacterium tuberculosis.

Metabolites synthesized by fatty acid synthases (FAS), polyketide synthases (PKS), and non-ribosomal peptide synthetases (NRPS) encompass a wide variety of complex organic compounds, which are extensively explored for their biological activities in the discovery of new therapeutic agents. In contrast, species of the genus Mycobacterium utilize their FAS systems in combination with PKS to produce essential components of the cell envelope and lipid virulence factors.

A crucial step in the biosynthesis of these metabolites is the post-translational modification of the acyl carrier protein (ACP) domain of these multi-enzyme systems. This modification is catalyzed by a 4′-phosphopantetheinyl transferase (PPTase), which transfers the phosphopantetheine (Ppant) moiety from a coenzyme A (CoA) molecule onto a strictly conserved serine residue of an ACP in the presence of Mg2+ or Mn2+ metal ions. The SH group at the extremity of the approximately 20 Å long Ppant then serves as an anchor for the elongation and modification of intermediates through interactions with other domains possessing distinct catalytic activities.

Although three-dimensional structures of PPTases, including PptT, are known, questions remained regarding the sequence of events preceding the activation of an ACP domain and the mechanism of Ppant transfer. This study provides a unique opportunity to retrace these events by combining an in-depth biophysical and structural analysis of the key steps in the Ppant transfer process with molecular dynamics simulations using a QM/MM force field, conducted in collaboration with researchers at LAAS.

Reference

Catalytic Cycle of Type II 4´-Phosphopantetheinyl Transferases. Sabine Gavalda*, Alexandre Faille*, Simone Fioccola*, Minh Chau Nguyen, Coralie Carivenc, Karine Rottier, Yann Rufin, Stéphane Saitta, Georges Czaplicki, Christophe Guilhot, Christian Chalut, Marie Brut#, Lionel Mourey# & Jean-Denis Pedelacq#. ACS Catalysis (2024) https://doi.org/10.1021/acscatal.3c06249

Contacts

CNRS Scientist | Jean-Denis Pedelacq | jean-denis.pedelacq@ipbs.fr
IPBS press | Françoise Viala | T +33 6 01 26 52 59 | communication@ipbs.fr

PptT in the spotlight: deciphering the mechanism of action of an essential enzyme from Mycobacterium tuberculosis