Bacterial Chromatin
Bacterial Chromatin
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细菌染色质
DOI：
10.1007/978-90-481-3473-1_4
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Hayes F
中科院分区：
文献类型：
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作者：
Hayes F
质粒是广泛分布于真细菌、古细菌和低等真核生物中的染色体外元件。质粒赋予携带它们的物种额外的遗传可塑性，但也具有重要的临床意义，因为抗生素抗性、毒力和其他疾病相关基因通常驻留在这些高度流动的元件上。此外，质粒是可塑性和信息丰富的模型，可以提高对细菌基因组分离的理解：细菌 DNA 分离的分子机制最适合描述低拷贝数质粒。分离体是驱动精确质粒分配的核蛋白复合物。该复合物通常包括： (i) 着丝粒类似物，其上发生segrosome组装； (ii) 多种位点特异性 DNA 结合因子之一，其识别其同源着丝粒并与其形成特定结构的核蛋白结构； (iii) ATP 结合蛋白，可以是肌动蛋白样，或更常见的是 ParA 超家族的 Walker 型 ATP 酶，它是原核生物特有的，并且组装成成熟的segrosome。 ATP 介导的肌动蛋白样分离蛋白聚合成双极纺锤体，引发双向丝状生长，在胞质分裂前以相反方向推动附着的质粒。质粒编码的 ParA 蛋白也会响应 ATP 结合而聚合，尽管支撑这种行为的分子机制以及这种聚合如何介导细胞内质粒运输仍有待充分阐明。最近对分离体组装和作用的深入的生化、结构和细胞生物学分析继续揭示了质粒分离的基本方面。
Plasmids are extrachromosomal elements that are widely distributed in eubacteria, as well as in archaea and lower eukaryotes. Plasmids confer additional genetic plasticity on species that harbour them, but also are of major clinical significance because antibiotic resistance, virulence, and other disease-associated genes often reside on these highly mobile elements. Moreover, plasmids are malleable and informative models to improve understanding of bacterial genome segregation: the molecular mechanisms of bacterial DNA segregation are best described for low copy number plasmids. The segrosome is the nucleoprotein complex that drives accurate plasmid partitioning. The complex typically includes: (i) a centromere analogue on which segrosome assembly occurs; (ii) one of a diverse array of site-specific DNA binding factors that recognizes its cognate centromere and with which it forms a nucleoprotein structure of specific architecture; and (iii) an ATP binding protein, either actin-like or, more commonly, a Walker-type ATPase of the ParA superfamily that is unique to prokaryotes and which assembles into the mature segrosome. ATP-mediated polymerization of actin-like segregation proteins into a bipolar spindle elicits bidirectional filament growth, propelling attached plasmids in opposing directions prior to cytokinesis. Plasmid-encoded ParA proteins also polymerize in response to ATP binding, although the molecular mechanisms that underpin this behaviour and how this polymerization mediates intracellular plasmid trafficking remain to be fully elucidated. Recent insightful biochemical, structural and cell biological analyses of segrosome assembly and action continue to unravel fundamental aspects of plasmid segregation.