Mutations in cell division proteins FtsZ and FtsA inhibit phiX174 protein-E-mediated lysis of Escherichia coli.

Electron microscopic studies emphasized that the protein-E-specific transmembrane tunnel structure, which permeabilizes Escherichia coli, is not randomly distributed over the cell envelope but is restricted to areas of potential division sites. These sites were located predominantly in the middle of the cell, but approximately one-third of these structures are found at the polar sites. Therefore, E. coli mutant strains with defects in cell division components were tested for their sensitivity to protein-E-mediated lysis. The ftsZ84 and the ftsA12 cell division mutant strains of E. coli were tolerant to protein-E-mediated lysis, whereas the ftsA3 mutant strain was lysed by protein E under conditions nonpermissive for division. The protein-E-tolerant phenotype of ftsZ84 and ftsA12 and the lysis-sensitive phenotype of other components of the septosome (e.g., ftsA3, ftsQ, and ftsI) suggest that initiation of cell division - rather than specific functions of cell division - plays an essential role in protein-E-mediated lysis. SulA-overproducing cells had a lysis-positive phenotype, the ring structure - but not the GTPase function - of FtsZ was impaired.