Department of Chemical and Biomolecular Engineering, Johns Hopkins Physical Sciences in Oncology Center, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA.
Mol Microbiol. 2010 Nov;78(3):651-68. doi: 10.1111/j.1365-2958.2010.07352.x. Epub 2010 Sep 20.
A key event in bacterial cytokinesis is the formation of the Z ring, which serves as a mechanical scaffold that recruits other cytokinetic proteins to establish functional divisomes. This scaffolding function of Z rings is essential throughout cytokinesis, but the underlying molecular interactions are poorly understood. Here we report that a widely conserved FtsZ binding protein, ZapA, has cytological, biochemical and biophysical properties that argue for the importance of cross-linking interactions between FtsZ polymers in the coherence of Z rings. Escherichia coli zapA null mutant cells have Z rings that are structurally looser and many helical precursors of Z rings fail to coalesce into coherent rings. Biophysical behaviour of FtsZ in the presence of ZapA reveals that ZapA not only bundles, but also cross-links FtsZ polymers, which makes it the first cross-linking protein of the bacterial cytoskeleton. Cross-linking in vitro occurs at the stoichiometry of FtsZ-ZapA interaction at the Z rings in vivo, where nearly all intracellular ZapA is dynamically associated. ZapA also stabilizes longitudinal bonds between FtsZ monomers since it promotes the polymerization of FtsZ mutants with lesions at the polymerization interface and since it reverses the inhibitory effects of SulA, a known antagonist of FtsZ longitudinal interactions.
在细菌胞质分裂过程中，一个关键事件是 Z 环的形成，它作为机械支架招募其他胞质分裂蛋白来建立功能性分裂体。Z 环的这种支架功能在胞质分裂过程中是必不可少的，但基础的分子相互作用还知之甚少。在这里，我们报告了一种广泛保守的 FtsZ 结合蛋白 ZapA，具有细胞学、生物化学和生物物理特性，表明 FtsZ 聚合物之间的交联相互作用对于 Z 环的连贯性非常重要。Escherichia coli zapA 缺失突变体细胞的 Z 环结构较松散，许多 Z 环的螺旋前体未能融合成连贯的环。在 ZapA 存在的情况下，FtsZ 的生物物理行为表明，ZapA 不仅可以束集 FtsZ 聚合物，还可以交联 FtsZ 聚合物，这使其成为细菌细胞骨架的第一个交联蛋白。体外交联发生在体内 Z 环处 FtsZ-ZapA 相互作用的化学计量比，其中几乎所有的细胞内 ZapA 都是动态相关的。ZapA 还稳定了 FtsZ 单体之间的纵向键，因为它促进了在聚合界面处具有病变的 FtsZ 突变体的聚合，并且它逆转了 SulA 的抑制作用，SulA 是 FtsZ 纵向相互作用的已知拮抗剂。
