Cooperative behavior of Escherichia coli cell-division protein FtsZ assembly involves the preferential cyclization of long single-stranded fibrils
Cooperative behavior of Escherichia coli cell-division protein FtsZ assembly involves the preferential cyclization of long single-stranded fibrils
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DOI：
10.1073/pnas.0409517102
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发表时间：
2005-02-08
影响因子：
11.1
通讯作者：
Rivas, G
中科院分区：
文献类型：
--
作者：
González, JM;Vélez, M;Rivas, G
提出了一种非合作（等键）组装与长聚合物优先环化相结合的机制，以解释之前提出的细菌细胞分裂蛋白FtsZ的单链细丝如何以明显合作的方式组装的问题。该建议是基于GTP介导的组装FtsZ从大肠杆菌，研究了在生理相关的稳态溶液条件下的沉降速度，原子力和电子显微镜，和沉淀试验的方法，包括测量的组合的结果。在多个蛋白质浓度进行的沉降速度实验揭示了一个基本上是双峰分布的缓慢沉降的物种和一个相对较窄的分布的快速沉降的物种，只出现在一个明显的“临界浓度”的蛋白质。在沉淀测定中，沉淀的蛋白质的量与在沉淀速度实验中观察到的快速沉淀物质的分数相关，随着超过临界浓度的蛋白质的总浓度线性增加。快速沉降部分的沉降系数与单链环状低聚物的存在定性一致，其大小范围约为50 -150个原聚体，类似于在原子力和电子显微镜照片中观察到的聚合物单链环。该模型与实验观测结果符合雅阁。
A mechanism of noncooperative (isodesmic) assembly coupled with preferential cyclization of long polymers is proposed to explain the previously posed question of how a single-stranded filament of the bacterial cell-division protein FtsZ can assemble in an apparently cooperative manner. This proposal is based on results of GTP-mediated assembly of FtsZ from Escherichia coli that was studied under physiologically relevant steady-state solution conditions by a combination of methods including measurement of sedimentation velocity, atomic force and electron microscopy, and precipitation assays. Sedimentation-velocity experiments carried out at multiple protein concentrations reveal an essentially bimodal distribution of slowly sedimenting species and a relatively narrow distribution of rapidly sedimenting species that appears only above an apparent "critical concentration" of protein. In a precipitation assay, the amount of protein that pellets, which correlates with the fraction of rapidly sedimenting species observed in sedimentation-velocity experiments, increases linearly with the total concentration of protein in excess of the critical concentration. Sedimentation coefficients of the rapidly sedimenting fraction are qualitatively consistent with the presence of single-stranded cyclic oligomers with a size range of approximate to50-150 protomers, similar to polymeric single-stranded rings observed in atomic force and electron micrographs. The proposed model is in accord with the results obtained from our experimental observations.