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首页> 外文期刊>Journal of bacteriology >The Structure and Assembly Dynamics of Plasmid Actin AlfA Imply a Novel Mechanism of DNA Segregation
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The Structure and Assembly Dynamics of Plasmid Actin AlfA Imply a Novel Mechanism of DNA Segregation

机译：质粒肌动蛋白AlfA的结构和组装动力学暗示DNA分离的新机制。

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Bacterial cytoskeletal proteins participate in a variety of processes, including cell division and DNA segregation. Polymerization of one plasmid-encoded, actin-like protein, ParM, segregates DNA by pushing two plasmids in opposite directions and forms the current paradigm for understanding active plasmid segregation. An essential feature of ParM assembly is its dynamically instability, the stochastic switching between growth and disassembly. It is unclear whether dynamic instability is an essential feature of all actin-like protein-based segregation mechanisms or whether bacterial filaments can segregate plasmids by different mechanisms. We expressed and purified AlfA, a plasmid-segregating actin-like protein from Bacillus subtilis, and found that it forms filaments with a unique structure and biochemistry; AlfA nucleates rapidly, polymerizes in the presence of ATP or GTP, and forms highly twisted, ribbon-like, helical filaments with a left-handed pitch and protomer nucleotide binding pockets rotated away from the filament axis. Intriguingly, AlfA filaments spontaneously associate to form uniformly sized, mixed-polarity bundles. Most surprisingly, our biochemical characterization revealed that AlfA does not display dynamic instability and is relatively stable in the presence of diphosphate nucleotides. These results (i) show that there is remarkable structural diversity among bacterial actin filaments and (ii) indicate that AlfA filaments partition DNA by a novel mechanism.
机译：细菌细胞骨架蛋白参与各种过程，包括细胞分裂和DNA分离。一种质粒编码的肌动蛋白样蛋白ParM的聚合通过向相反方向推动两个质粒来分离DNA，形成了理解活性质粒分离的当前范例。 ParM组装的基本特征是它的动态不稳定，增长与分解之间的随机切换。目前尚不清楚动态不稳定性是否是所有基于肌动蛋白的蛋白质分离机制的基本特征，还是细菌细丝是否可以通过不同机制分离质粒。我们从枯草芽孢杆菌中表达并纯化了一个质粒分离的肌动蛋白样蛋白AlfA，发现它形成具有独特结构和生化特性的细丝。 AlfA迅速成核，在ATP或GTP存在下聚合，并形成高度扭曲的，带状螺旋状细丝，其左旋螺距和远离细丝轴旋转的原核核苷酸结合口袋。有趣的是，AlfA细丝自发地结合形成均匀大小的混合极性束。最令人惊讶的是，我们的生化特征表明AlfA不会显示动态不稳定性，并且在存在二磷酸核苷酸的情况下相对稳定。这些结果（i）表明细菌肌动蛋白丝之间存在显着的结构多样性，并且（ii）表明AlfA丝通过新的机理分配DNA。

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