Abstract
The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery, and orchestrates membrane and peptidoglycan cell wall invagination. However, the mechanism for FtsZ regulation of peptidoglycan metabolism is unknown. The FtsZ GTPase domain is separated from its membrane-anchoring C-terminal conserved (CTC) peptide by a disordered C-terminal linker (CTL). Here, we investigate CTL function in Caulobacter crescentus. Strikingly, production of FtsZ lacking the CTL (ΔCTL) is lethal: cells become filamentous, form envelope bulges, and lyse, resembling treatment with β-lactam antibiotics. This phenotype is produced by FtsZ polymers bearing the CTC and a CTL shorter than 14 residues. Peptidoglycan synthesis still occurs downstream of ΔCTL, however cells expressing ΔCTL exhibit reduced peptidoglycan crosslinking and longer glycan strands than wildtype. Importantly, midcell proteins are still recruited to sites of ΔCTL assembly. We propose that FtsZ regulates peptidoglycan metabolism through a CTL-dependent mechanism that extends beyond simple protein recruitment.
Highlights
The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery and orchestrates membrane and peptidoglycan cell wall invagination
The FtsZ monomer can be divided into four regions: (i) a short N-terminal peptide, (ii) a conserved GTPase domain essential for polymerization, (iii) an intrinsically disordered C-terminal linker (CTL) and (iv) a C-terminal conserved peptide (CTC) that interacts with membranetethering proteins (Fig. 1a)[18]
To investigate the function of the CTL in C. crescentus, we engineered a panel of C. crescentus FtsZ CTL variants bearing the wild-type (WT) C. crescentus CTL (CcCTL), three other a-proteobacterial CTLs (from Hyphomonas neptunium (HnCTL), Rickettsia parkeri (RpCTL) or Magnetospirillum magneticum (MmCTL)), or the much shorter E. coli CTL (EcCTL) in place of the C. crescentus CTL (Table 1, Supplementary Fig. 1)
Summary
The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery and orchestrates membrane and peptidoglycan cell wall invagination. On the basis of these findings, a mechanical role for FtsZ in inner membrane constriction has been proposed It is not known whether force generation by FtsZ is required in vivo, nor is it clear how FtsZ-mediated force might be coupled to PG remodelling to coordinately invaginate the multiple layers of the cell envelope during cytokinesis[13]. We set out to understand the physiological significance of the long CTL in C. crescentus FtsZ, and in the process uncovered a surprising requirement for the FtsZ CTL in regulating specific aspects of PG remodelling From these findings, we propose that FtsZ regulates PG metabolism through a CTL-dependent mechanism that is in addition to its ability to recruit proteins to midcell
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