Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, 725 N. Wolfe St, Baltimore, MD, 21205, USA.
ITQB NOVA, Universidade NOVA de Lisboa, Lisbon, Av. da República, 2780-157, Oeiras, Portugal.
Nat Commun. 2023 Jul 31;14(1):4585. doi: 10.1038/s41467-023-39921-4.
The bacterial divisome is a macromolecular machine composed of more than 30 proteins that controls cell wall constriction during division. Here, we present a model of the structure and dynamics of the core complex of the E. coli divisome, supported by a combination of structure prediction, molecular dynamics simulation, single-molecule imaging, and mutagenesis. We focus on the septal cell wall synthase complex formed by FtsW and FtsI, and its regulators FtsQ, FtsL, FtsB, and FtsN. The results indicate extensive interactions in four regions in the periplasmic domains of the complex. FtsQ, FtsL, and FtsB support FtsI in an extended conformation, with the FtsI transpeptidase domain lifted away from the membrane through interactions among the C-terminal domains. FtsN binds between FtsI and FtsL in a region rich in residues with superfission (activating) and dominant negative (inhibitory) mutations. Mutagenesis experiments and simulations suggest that the essential domain of FtsN links FtsI and FtsL together, potentially modulating interactions between the anchor-loop of FtsI and the putative catalytic cavity of FtsW, thus suggesting a mechanism of how FtsN activates the cell wall synthesis activities of FtsW and FtsI.
细菌分裂体是一种由 30 多种蛋白质组成的大分子机器，它控制着细胞分裂过程中的细胞壁收缩。在这里，我们提出了一个大肠杆菌分裂体核心复合物的结构和动力学模型，该模型得到了结构预测、分子动力学模拟、单分子成像和突变分析的支持。我们专注于由 FtsW 和 FtsI 形成的隔膜细胞壁合成酶复合物，以及其调节剂 FtsQ、FtsL、FtsB 和 FtsN。结果表明，在复合物的周质域的四个区域中存在广泛的相互作用。FtsQ、FtsL 和 FtsB 支持 FtsI 处于伸展构象，通过 C 末端结构域之间的相互作用，将 FtsI 转肽酶结构域从膜中抬起。FtsN 结合在 FtsI 和 FtsL 之间富含分裂前（激活）和显性负（抑制）突变的残基的区域。突变实验和模拟表明，FtsN 的必需结构域将 FtsI 和 FtsL 连接在一起，可能调节 FtsI 的锚环与 FtsW 的假定催化腔之间的相互作用，从而提出了 FtsN 如何激活 FtsW 和 FtsI 的细胞壁合成活性的机制。
