Disruption of salt bridge interactions in the inter-domain cleft of the tubulin-like protein FtsZ of Escherichia coli makes cells sensitive to the cell division inhibitor PC190723.

FtsZ forms a ring-like assembly at the site of division in bacteria. It is the first protein involved in the formation of the divisome complex to split the cell into two halves, indicating its importance in bacterial cell division. FtsZ is an attractive target for developing new anti-microbial drugs to overcome the challenges of antibiotic resistance. The most potent inhibitor against FtsZ is PC190723, which is effective against all strains and species of Staphylococcus, including the methicillin- and multi-drug-resistant Staphylococcus aureus and strains of Bacillus. However, FtsZs from bacteria such as E. coli, Streptococcus, and Enterococcus were shown to be resistant to this inhibitor. In this study, we provide further evidence that the three pairwise bridging interactions, between residues S227 and G191, R307 and E198 and D299 and R202, between S7, S9, S10 β-strands and the H7 helix occlude the inhibitor from binding to E. coli FtsZ. We generated single, double and triple mutations to disrupt those bridges and tested the effectiveness of PC190723 directly on Z-ring assembly in vivo. Our results show that the disruption of S227-G191 and R307-E198 bridges render EcFtsZ highly sensitive to PC190723 for Z-ring assembly. Ectopic expression of the double mutants, FtsZ S227I R307V results in hypersensitivity of the susceptible E. coli imp4213 strain to PC190723. Our studies could further predict the effectiveness of PC190723 or its derivatives towards FtsZs of other bacterial genera.