Abstract

FtsZ is a highly conserved cytoskeletal protein that is essential for organizing the cell division machinery in bacteria. The first observable step in cytokinesis, FtsZ forms a ring at the future division site. The FtsZ ring serves as a platform for recruitment of other division proteins. FtsZ has three major domains: a tubulin-like GTP binding core domain, an intrinsically disordered C-terminal linker (CTL), and a conserved ~11-residue motif known as the C-terminal peptide (CTP). The core domain is sufficient for head-to tail assembly of FtsZ polymers in vitro. The CTP interacts with modulatory proteins to coordinate division, while the CTL tethers the core and CTP together. Although the CTL is essential, it has no defined structure, nor is it conserved in sequence or length. Changes to the CTL can dramatically impact division, suggesting a role beyond a mere tether. I sought to understand what aspects of the CTL are essential for FtsZ function in a collaboration with the Pappu lab. While disordered regions lack typical 3D structures, sequence features such as the distribution of charged amino acids can be manipulated to change how these regions sample 3D space. To test the impact of CTL charge distribution on FtsZ function, we generated CTL mutants with varying degrees of mixed and segregated positive and negative amino acids. I found that even subtle changes to the CTL can dramatically change FtsZ assembly dynamics and Z ring architecture. Simulation data further revealed that the CTP is likely to transiently interact with the FtsZ core in a CTL-mediated fashion. During this study, we identified two CTL mutants, designated FtsZκ14 and FtsZκ53, that support B. subtilis division at protein levels that are 27% and 22% of wild type FtsZ (FtsZWT). This was surprising, as previous work establishes FtsZ assembly as a concentration dependent phenomenon. Based on these findings and other data, I hypothesized that FtsZκ14 and FtsZκ53 are able to form polymers at concentrations well below wild type FtsZ. My in vitro data support this model, indicating that subunit interaction is significantly improved over wild type for both FtsZκ14 and FtsZκ53 albeit through different mechanisms. Together, these data suggest that the ftsZκ14 and ftsZκ53 mutations compensate for their impact on protein stability by enhancing FtsZ assembly potential. My biochemical data further support our previous simulation data suggesting the C-terminal linker modulates contacts between the CTP and the core to regulate assembly kinetics.

Committee Chair

Petra Levin

Committee Members

Joe Jez; Ram Dixit; Silvia Jansen; Susan Dutcher

Degree

Doctor of Philosophy (PhD)

Author's Department

Biology & Biomedical Sciences (Plant & Microbial Biosciences)

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

4-17-2026

Language

English (en)

Author's ORCID

https://orcid.org/0000-0002-0888-8011

Download

Available for download on Friday, October 16, 2026

Included in

Microbiology Commons

Share

COinS