Johnson Jay E, Lackner Laura L, Hale Cynthia A, de Boer Piet A J
Department of Molecular Biology and Microbiology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4960, USA.
J Bacteriol. 2004 Apr;186(8):2418-29. doi: 10.1128/JB.186.8.2418-2429.2004.
The MinC division inhibitor is required for accurate placement of the septal ring at the middle of the Escherichia coli cell. The N-terminal domain of MinC ((Z)MinC) interferes with FtsZ assembly, while the C-terminal domain ((D)MinC) mediates both dimerization and complex formation with either MinD or DicB. Binding to either of these activators greatly enhances the division-inhibitory activity of MinC in the cell. The MinD ATPase plays a crucial role in the rapid pole-to-pole oscillation of MinC that is proposed to force FtsZ ring formation to midcell. DicB is encoded by one of the cryptic prophages on the E. coli chromosome (Qin) and is normally not synthesized. Binding of MinD or DicB to (D)MinC produces complexes that have high affinities for one or more septal ring-associated targets. Here we show that the FtsZ-binding protein ZipA is required for both recruitment of the (D)MinC/DicB complex to FtsZ rings and the DicB-inducible division block normally seen in MinC(+) cells. In contrast, none of the known FtsZ-associated factors, including ZipA, FtsA, and ZapA, appear to be specifically required for targeting of the (D)MinC/MinD complex to rings, implying that the two MinC/activator complexes must recognize distinct features of FtsZ assemblies. MinD-dependent targeting of MinC may occur in two steps of increasing topological specificity: (i) recruitment of MinC from the cytoplasm to the membrane, and (ii) specific targeting of the MinC/MinD complex to nascent septal ring assemblies on the membrane. Using membrane-tethered derivatives of MinC, we obtained evidence that both of these steps contribute to the efficiency of MinC/MinD-mediated division inhibition.
MinC分裂抑制剂对于隔膜环精确位于大肠杆菌细胞中部是必需的。MinC的N端结构域（(Z)MinC）干扰FtsZ组装，而C端结构域（(D)MinC）介导二聚化以及与MinD或DicB形成复合物。与这些激活因子中的任何一个结合都会大大增强MinC在细胞中的分裂抑制活性。MinD ATP酶在MinC的快速极到极振荡中起关键作用，这种振荡被认为可迫使FtsZ环在细胞中部形成。DicB由大肠杆菌染色体上的一个隐蔽原噬菌体（Qin）编码，通常不合成。MinD或DicB与(D)MinC结合产生对一个或多个与隔膜环相关的靶标具有高亲和力的复合物。我们在此表明，FtsZ结合蛋白ZipA对于将(D)MinC/DicB复合物募集到FtsZ环以及MinC(+)细胞中通常可见的DicB诱导的分裂阻滞都是必需的。相比之下，包括ZipA、FtsA和ZapA在内的所有已知FtsZ相关因子似乎都不是将(D)MinC/MinD复合物靶向到环所特别必需的，这意味着两种MinC/激活因子复合物必须识别FtsZ组装的不同特征。MinC的MinD依赖性靶向可能通过增加拓扑特异性的两个步骤发生：(i) 将MinC从细胞质募集到膜上，以及(ii) 将MinC/MinD复合物特异性靶向到膜上新生的隔膜环组装体。使用MinC的膜 tethered 衍生物，我们获得的证据表明这两个步骤都有助于MinC/MinD介导的分裂抑制效率。
