Bacteriophage Kil peptide folds into a predicted helix-turn-helix structure to disrupt Escherichia coli cell division

FtsZ, a eukaryotic tubulin homolog and an essential component of the bacterial divisome, is the target of numerous antimicrobial compounds as well as proteins and peptides, most of which inhibit FtsZ polymerization dynamics. We previously showed that the Kil peptide from bacteriophage lambda; inhibits Escherichia coli cell division by disrupting FtsZ ring assembly, and this inhibition requires the presence of the essential FtsZ membrane anchor protein ZipA. To investigate the Kil molecular mechanism further, we employed truncation mutants and molecular modeling to identify the minimal residues necessary for its activity. Modeling suggests that the Kil core segment folds into a helix-turn-helix (HTH) structure. Deleting either the C-terminal 11 residues or the N-terminal 5 residues of Kil still allowed inhibition of E. coli cell division, but removing both termini nearly abolished this activity, indicating that a minimal region within the Kil HTH core is essential for its function. Another Kil-like peptide from a closely related enterobacterial phage also disrupts FtsZ ring assembly and requires ZipA for this activity. Consistent with its broader activity against FtsZ, lambda Kil was able to efficiently inhibit cell division of a uropathogenic E. coli (UPEC) strain. Understanding the function of Kil and similar peptides can potentially reveal how FtsZ functions in bacterial cell division and additional ways to target FtsZ for antimicrobial therapies.