Protein scaffold involving MSMEG_1285 maintains cell wall organization and mediates penicillin sensitivity in mycobacteria.

Protein-protein interactions are key in mycobacterial physiology, notably during the biosynthesis of the very peculiar mycobacterial cell wall. In this paper, we demonstrate that MSMEG_1285 interacts with PonA1, a bifunctional penicillin-binding protein involved in peptidoglycan biosynthesis. Deletion of MSMEG_1285 enhances Mycobacterium smegmatis resistance to penicillin antibiotics, a phenotype that is exacerbated by the additional deletion of hbhA. This also led to a substantial decrease in the amounts of porins in the cell wall, which are necessary for the import of small and hydrophilic β-lactams. Deletion of both MSMEG_1285 and hbhA provoked an over-representation of several enzymes involved in peptidoglycan degradation. Thus, we propose that MSMEG_1285 is part of a protein scaffold, which also involves PonA1 and HbhA, and that it is responsible for the tight regulation of peptidoglycan hydrolysis. This study provides a better understanding of the mycobacterial physiology, which is an essential step for strengthening the action of drugs that specifically target peptidoglycan biosynthesis.