Structural Polymorphism of the ParM Filament and Dynamic Instability
Structural Polymorphism of the ParM Filament and Dynamic Instability
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DOI：
10.1016/j.str.2009.07.008
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发表时间：
2009-09-09
期刊：
影响因子：
5.7
通讯作者：
Egelman, Edward H.
中科院分区：
文献类型：
--
作者：
Galkin, Vitold E.;Orlova, Albina;Egelman, Edward H.
细菌中R1质粒的分离依赖于ParM，一种肌动蛋白同源物，通过在聚合和解聚循环之间切换来分离质粒。我们发现在ATP或GTP存在下相似的聚合动力学和稳定性，并且ATP比GTP有10倍的亲和偏好。我们使用电子冷冻显微镜来评估ParM细丝的异质性。除了变扭外，ParM还具有变轴向升，并且这两个参数是耦合的。在相同的ParM纤维中，亚基可以以两种不同的结构状态存在，核苷酸结合间隙关闭或打开，并且结合的核苷酸会影响状态的分布。在这两种状态下，原蛋白之间的界面是不同的，并且在这两种状态下它都不类似于f -肌动蛋白。我们的研究结果表明，裂缝的闭合状态是ParM聚合所必需的，但不是充分的，并为ParM长丝的动态不稳定性提供了结构基础。
Segregation of the R1 plasmid in bacteria relies on ParM, an actin homolog that segregates plasmids by switching between cycles of polymerization and depolymerization. We find similar polymerization kinetics and stability in the presence of either ATP or GTP and a 10-fold affinity preference for ATP over GTP. We used electron cryo-microscopy to evaluate the heterogeneity within ParM filaments. In addition to variable twist, ParM has variable axial rise, and both parameters are coupled. Subunits in the same ParM filaments can exist in two different structural states, with the nucleotide-binding cleft closed or open, and the bound nucleotide biases the distribution of states. The interface between protomers is different between these states, and in neither state is it similar to F-actin. Our results suggest that the closed state of the cleft is required but not sufficient for ParM polymerization, and provide a structural basis for the dynamic instability of ParM filaments.