Marrington Rachel, Small Elaine, Rodger Alison, Dafforn Timothy R, Addinall Stephen G
Department of Chemistry, University of Warwick, Coventry CV4 7AL, School of Biological Sciences, Michael Smith Building, Oxford Road, Manchester M13 9PT, United Kingdom.
J Biol Chem. 2004 Nov 19;279(47):48821-9. doi: 10.1074/jbc.M404944200. Epub 2004 Aug 23.
Polymer formation by the essential FtsZ protein plays a crucial role in the cytokinesis of most prokaryotes. Lateral associations between these FtsZ polymers to form bundles or sheets are widely predicted to be extremely important for FtsZ function in vivo. We have carried out a study in vitro of FtsZ polymer formation and bundling using linear dichroism (LD) to assess structural properties of the polymers. We demonstrate proof-of-principle experiments to show that LD can be used as a technique to follow FtsZ polymerization, and we present the LD spectra of FtsZ polymers. Our subsequent examination of FtsZ polymer bundling induced by calcium reveals a substantial increase in the LD signal indicative of increased polymer length and rigidity. We also detect a specific conformational change in the guanine moiety associated with bundling, whereas the conformation and configuration of the FtsZ monomers within the polymer remain largely unchanged. We demonstrate that other divalent cations can induce this conformational change in FtsZ-bound GTP coincident with polymer bundling. Therefore, we present "flipping" of the guanine moiety in FtsZ-bound GTP as a mechanism that explains the link between reduced GTPase activity, increased polymer stability, and polymer bundling.
必需的FtsZ蛋白形成聚合物在大多数原核生物的胞质分裂中起着关键作用。这些FtsZ聚合物之间形成束状或片状的横向关联被广泛认为对FtsZ在体内的功能极为重要。我们利用线性二色性（LD）对FtsZ聚合物的形成和聚集进行了体外研究，以评估聚合物的结构特性。我们进行了原理验证实验，表明LD可作为跟踪FtsZ聚合的技术，并给出了FtsZ聚合物的LD光谱。我们随后对钙诱导的FtsZ聚合物聚集的研究表明，LD信号大幅增加，表明聚合物长度和刚性增加。我们还检测到与聚集相关的鸟嘌呤部分的特定构象变化，而聚合物内FtsZ单体的构象和构型基本保持不变。我们证明其他二价阳离子可在聚合物聚集的同时诱导FtsZ结合的GTP发生这种构象变化。因此，我们提出FtsZ结合的GTP中鸟嘌呤部分的“翻转”作为一种机制，解释了GTP酶活性降低、聚合物稳定性增加和聚合物聚集之间的联系。
