Assembly Dynamics of Mycobacterium tuberculosis FtsZ

Department of Cell Biology, Duke University, Medical Center, Durham, North Carolina 27710, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 10/2007; 282(38):27736-43. DOI: 10.1074/jbc.M703788200
Source: PubMed


We have investigated the assembly of FtsZ from Mycobacterium tuberculosis (MtbFtsZ). Electron microscopy confirmed the previous observation that MtbFtsZ assembled into long, two-stranded filaments at pH 6.5. However, we found that assembly at pH 7.2 or 7.7 produced predominantly short, one-stranded protofilaments, similar to those of Escherichia coli FtsZ (EcFtsZ). Near pH 7, which is close to the pH of M. tuberculosis cytoplasm, MtbFtsZ formed a mixture of single- and two-stranded filaments. We developed a fluorescence resonance energy transfer assay to measure the kinetics of initial assembly and the dynamic properties at steady state. Assembly of MtbFtsZ reached a plateau after 60-100 s, about 10 times slower than EcFtsZ. The initial assembly kinetics were similar at pH 6.5 and 7.7, despite the striking difference in the polymer structures. Both were fit with a cooperative assembly mechanism involving a weak dimer nucleus, similar to EcFtsZ but with slower kinetics. Subunit turnover and GTPase at steady state were also about 10 times slower for MtbFtsZ than for EcFtsZ. Specifically, the half-time for subunit turnover in vitro at pH 7.7 was 42 s for MtbFtsZ compared with 5.5 s for EcFtsZ. Photobleaching studies in vivo showed a range of turnover half-times with an average of 25 s for MtbFtsZ as compared with 9 s for EcFtsZ.

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Available from: Yaodong Chen, Aug 23, 2014
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    • "Through this simple mechanism, which is basically energy neutral, we believe that the Zring is constantly exerting a constriction force on the membrane and that constriction finally occurs when the peptidoglycan remodeling permits the wall to follow this force [M€ oll et al., 2010]. A constant constriction force is consistent with the high turnover of FtsZ observed by F€ orster resonance energy transfer (FRET) [Chen et al., 2005, 2007]. Other FtsZ associated proteins may further fine tune the operation [Peters et al., 2007]. "
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    • "This is consistent with the absence of spatial regulation by Min system in mycobacteria. However, the FtsZ ring is still the determinant in establishing division site as previously reported (Dziadek et al. 2003; Chen et al. 2007). Despite either the asymmetric or random selection of the division site, the completion of division of mycobacteria produces predominantly normal sized cells with an intact genome content (in the absence of any nucleoidocclusion function). "
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    • "MtFtsZ has been reported to display a reduced GTPase activity (White et al. 2000) and a concomitant reduction in the rate of filament turnover in vivo (Chen et al. 2007). Consistently, rings and cables of MtFtsZ displayed a significant increase in t 1/2 in FRAP experiments (Fig. 1D,E; Supplemental Table 1), suggesting that MtFtsZ was potentially using similar mechanisms of assembly and polymerization in fission yeast. "
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