Rapid in Vitro Assembly of Caulobacter crescentus FtsZ Protein at pH 6.5 and 7.2

FtsZ from most bacteria assembles rapidly in vitro , reaching a steady-state plateau in 5–10 s after addition of GTP. A recent study used a novel dynamic light-scattering technique to assay the assembly of FtsZ from Caulobacter crescentus (CcFtsZ) and reported that assembly required 10 min, ∼100 times slower than for related bacteria. Previous studies had indicated normal, rapid assembly of CcFtsZ. We have reinvestigated the assembly kinetics using a mutant L72W, where assembly of subunits into protofilaments results in a significant increase in tryptophan fluorescence. We found that assembly reached a plateau in 5–10 s and showed no change in the following 10 min. This was confirmed by 90° light scattering and negative-stain electron microscopy. The very slow kinetics in the dynamic light-scattering study may be related to a refractory state induced when the FtsZ protein is stored without nucleotide, a phenomenon that we had observed in a previous study of EcFtsZ. We conclude that CcFtsZ is not an outlier, but shows rapid assembly kinetics similar to FtsZ from related bacteria. Background: A recent study reported that Caulobacter crescentus FtsZ (CcFtsZ) required 10 min to reach a plateau, 10–100 times slower than other bacteria. Results: We assayed assembly of CcFtsZ and found that it reached steady state in 5–10 s. Conclusion: The slow kinetics in the previous study may have resulted from nucleotide deprivation. Significance: CcFtsZ assembly kinetics are similar to those of other bacteria.