<i>Mycobacterium tuberculosis</i> FtsB and PerM interact via a C-terminal helix in FtsB to modulate cell division

Latent infection by <i>Mycobacterium tuberculosis</i> (Mtb) impedes effective tuberculosis therapy and eradication. The protein PerM is essential for chronic Mtb infections in mice and acts via the divisome protein FtsB to modulate cell division. Using transgenic co-expression in <i>Escherichia coli</i>, we studied the Mtb PerM-FtsB interaction in isolation from other Mtb proteins, engineering PerM to enhance expression in the <i>E. coli</i> membrane. Using fluorescence microscopy in <i>E. coli</i>, we observed that the previously reported PerM-dependent instability of Mtb FtsB required a segment of FtsB predicted to bind cell-division proteins FtsL and FtsQ. Furthermore, we found that the stability of membrane-localized PerM hinged on its interaction with a conserved, C-terminal helix in FtsB. We also observed that removing this helix disrupted PerM-FtsB interaction using single-molecule tracking. Molecular dynamics results supported the observation that FtsB stabilized PerM and suggested that interactions at the PerM-FtsB interface differ from our initial structure prediction in a way that is consistent with PerM sequence conservation. Although narrowly conserved, the PerM-FtsB interaction emerges as a potential therapeutic target for persistent infections by disrupting the regulation of cell division. Integrating protein structure prediction, molecular dynamics, and single-molecule microscopy, our approach is primed to screen potential inhibitors of the PerM-FtsB interaction and can be straightforwardly adapted to explore other putative interactions.IMPORTANCEOur research reveals significant insights into the dynamic interaction between the proteins PerM and FtsB within <i>Mycobacterium tuberculosis</i>, contributing to our understanding of bacterial cell division mechanisms crucial for infection persistence. By combining innovative fluorescence microscopy and molecular dynamics, we established that the stability of these proteins is interdependent; molecular dynamics placing PerM-FtsB in the context of the mycobacterial divisome shows how disrupting PerM-FtsB interactions can plausibly impact bacterial cell wall synthesis. These findings highlight the PerM-FtsB interface as a promising target for novel therapeutics aimed at combating persistent bacterial infections. Importantly, our approach can be adapted for similar studies in other bacterial systems, suggesting broad implications for microbial biology and antibiotic development.