In vitro assembly studies of FtsZ/tubulin-like proteins (TubZ) from Bacillus plasmids: evidence for a capping mechanism.
Proteins with a weak sequence similarity to tubulin and FtsZ are expressed from large plasmids of Bacillus anthracis and Bacillus thuringiensis and are probably involved in plasmid segregation. Previously designated RepX and TubZ, we designate them here as TubZ-Ba and TubZ-Bt. We have expressed and purified the proteins for in vitro studies. TubZ-Ba and TubZ-Bt share only 21% amino acid identity, but they have remarkably similar biochemical properties. They both assemble into two-stranded filaments and larger bundles above a critical concentration, and they hydrolyze GTP at a very high rate, approximately 20 GTP min(-1) TubZ(-1). Assembly is also supported by GTPgammaS. A tiny amount of GTPgammaS stabilizes polymers assembled in GTP and inhibits the GTPase by a mechanism involving cooperativity. The nucleotide in the polymers is almost 100% GDP, which is similar to microtubules but very different from the 20-30% GDP in FtsZ polymers. This suggests that the TubZ polymers have a capping mechanism that may be related to the GTP cap that produces dynamic instability of microtubules.
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- Tubulin
- Plasmids
- Microscopy, Electron
- Guanosine Triphosphate
- GTP Phosphohydrolases
- Escherichia coli Proteins
- Cytoskeletal Proteins
- Biochemistry & Molecular Biology
- Bacterial Proteins
- Bacillus thuringiensis
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- Tubulin
- Plasmids
- Microscopy, Electron
- Guanosine Triphosphate
- GTP Phosphohydrolases
- Escherichia coli Proteins
- Cytoskeletal Proteins
- Biochemistry & Molecular Biology
- Bacterial Proteins
- Bacillus thuringiensis