Treadmilling of a prokaryotic tubulin-like protein, TubZ, required for plasmid stability in Bacillus thuringiensis
Treadmilling of a prokaryotic tubulin-like protein, TubZ, required for plasmid stability in Bacillus thuringiensis
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DOI：
10.1101/gad.1546107
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发表时间：
2007-06-01
影响因子：
10.5
通讯作者：
Pogliano, Joe
中科院分区：
文献类型：
--
作者：
Larsen, Rachel A.;Cusumano, Christina;Pogliano, Joe
原核生物依赖于远距离微管蛋白同系物FtsZ来组装细胞分裂所必需的细胞动力学环，但通常认为其缺乏参与DNA分离等过程的微管蛋白样聚合物.在这里，我们表征的蛋白质（TubZ）从苏云金芽孢杆菌毒力质粒pBtoxis，这是一个成员的微管蛋白/ FtsZ的GTubulin超家族，但只有远亲FtsZ和微管蛋白。TubZ组装动态的线性聚合物，这些聚合物具有正负端的定向聚合、通过螺旋研磨的移动以及组装的临界浓度。改变T7环内高度保守的催化残基的点突变（D269 A）完全消除了反式研磨并允许在比野生型蛋白低得多的蛋白浓度下形成稳定的聚合物。当以反式表达时，TubZ（D269 A）与野生型TubZ共组装并显著降低pBtoxis的稳定性，证明TubZ动力学与质粒维持之间的直接相关性。tubZ基因与tubR在一个操纵子中，tubR编码一种推定的DNA结合蛋白，调节TubZ水平。我们的研究结果表明，TubZ是一类新的原核细胞骨架蛋白质的代表，重要的质粒稳定性，很久以前从古老的微管蛋白/ FtsZ祖先分歧。
Prokaryotes rely on a distant tubulin homolog, FtsZ, for assembling the cytokinetic ring essential for cell division, but are otherwise generally thought to lack tubulin- like polymers that participate in processes such as DNA segregation. Here we characterize a protein (TubZ) from the Bacillus thuringiensis virulence plasmid pBtoxis, which is a member of the tubulin/ FtsZ GTPase superfamily but is only distantly related to both FtsZ and tubulin. TubZ assembles dynamic, linear polymers that exhibit directional polymerization with plus and minus ends, movement by treadmilling, and a critical concentration for assembly. A point mutation (D269A) that alters a highly conserved catalytic residue within the T7 loop completely eliminates treadmilling and allows the formation of stable polymers at a much lower protein concentration than the wild- type protein. When expressed in trans, TubZ(D269A) coassembles with wild-type TubZ and significantly reduces the stability of pBtoxis, demonstrating a direct correlation between TubZ dynamics and plasmid maintenance. The tubZ gene is in an operon with tubR, which encodes a putative DNA- binding protein that regulates TubZ levels. Our results suggest that TubZ is representative of a novel class of prokaryotic cytoskeletal proteins important for plasmid stability that diverged long ago from the ancient tubulin/ FtsZ ancestor.