In vitro assembly studies of FtsZ/Tubulin-like proteins (TubZ) from Bacillus plasmids -: Evidence for a capping mechanism
In vitro assembly studies of FtsZ/Tubulin-like proteins (TubZ) from Bacillus plasmids -: Evidence for a capping mechanism
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DOI：
10.1074/jbc.m709163200
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发表时间：
2008-03-28
影响因子：
4.8
通讯作者：
Erickson, Harold P.
中科院分区：
文献类型：
--
作者：
Chen, Yaodong;Erickson, Harold P.
在炭疽芽孢杆菌和苏云金芽孢杆菌的大质粒中表达了与微管蛋白和FtsZ序列相似性较弱的蛋白，这些蛋白可能参与了质粒分离。以前被指定为RepX和TubZ，我们在这里将它们指定为TubZ- ba和TubZ- bt。我们已经表达和纯化了用于体外研究的蛋白质。TubZ-Ba和TubZ-Bt只有21%的氨基酸相同，但它们具有非常相似的生化特性。在临界浓度以上，它们都聚集成两股细丝和更大的束，并且它们以非常高的速率水解GTP，类似于20 GTP min(-1) TubZ（-1）。GTP γ S也支持组装，少量的GTP γ S稳定组装在GTP中的聚合物，并通过一种涉及协同作用的机制抑制GTP酶。聚合物中的核苷酸几乎是100%的GDP，这与微管相似，但与FtsZ聚合物中的20-30%的GDP有很大不同。这表明TubZ聚合物具有一种封盖机制，可能与GTP封盖有关，该封盖会产生微管的动态不稳定性。
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, similar to 20 GTP min(-1) TubZ(-1). Assembly is also supported by GTP gamma S. A tiny amount of GTP gamma S 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.