MinC Protein Shortens FtsZ Protofilaments by Preferentially Interacting with GDP-bound Subunits

Evidence That Bacteriophage λ Kil Peptide Inhibits Bacterial Cell Division by Disrupting FtsZ Protofilaments and Sequestering Protein Subunits

“…Parallel analysis in which the diffusion time and contribution of the free dye were allowed to flow did not significantly affect the relative contributions and diffusion times of the other components in the fit. Traces acquired for samples containing unlabeled Kil peptide in addition to FtsZ-GTP were found to be well described by this three-component model, allowing calculation of an average diffusion coefficient ͗D͘ as a weighted mean of the D i corresponding to the FtsZ species, as described previously for samples containing other antagonists (21). This ͗D͘ was normalized by the difference between values corresponding to FtsZ-GDP samples and FtsZ-GTP samples lacking Kil peptide, thus obtaining a D norm value (21).…”

“…For each sample, five autocorrelation traces were acquired for 1 min each and globally analyzed using FFS Data Processor software (version 2.4 extended, Scientific Software Technologies Center, Belarus) (43), essentially as described previously for equivalent traces of FtsZ-GDP and FtsZ-GTP obtained under two photon excitation (8,21,33). In addition to the diffusion components, a term for the time-dependent population and depopulation of the tracer triplet state was also included in this case as shown in Equation 1,…”

“…As in previous studies (8,21,33), a model involving two diffusion components assigned to free dye ( i independently determined and fixed and F i Ͻ0.2) and to unassembled FtsZ protein (D i ϭ 55 Ϯ 5 m 2 s Ϫ1 ) was used for FtsZ-GDP samples. For the FtsZ-GTP samples, a three-component model was used, with components assigned to free dye (F i fixed to that determined from analysis of the FtsZ-GDP traces), unassembled FtsZ ( i fixed to that determined for FtsZ-GDP), and protofilaments ( i and F i were free parameters in the fits).…”

“…The molecular mechanism underlying FtsZ polymerization inhibition by MinC has been widely studied using biochemical, biophysical, and structural approaches (18 -21). This antagonist reduces the size of FtsZ protofilaments maintaining a narrow distribution of sizes, likely affecting subunit turnover (21). All published studies agree that MinC does not modify FtsZ GTPase activity (17,21).…”

“…This antagonist reduces the size of FtsZ protofilaments maintaining a narrow distribution of sizes, likely affecting subunit turnover (21). All published studies agree that MinC does not modify FtsZ GTPase activity (17,21). Nucleoid occlusion is mediated by SlmA, a sequence-specific DNA-binding protein that interferes with FtsZ assembly preventing Z-ring formation in the vicinity of the nucleoid (22).…”