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Abstract：
The FtsQBL is an essential molecular complex sitting midway through bacterial divisome assembly. To visualize and understand its structure, and the consequences of its membrane anchorage, we produced a model of the E. coli complex using the deep-learning prediction utility, AlphaFold 2. The heterotrimeric model was inserted into a 3-lipid model membrane and subjected to a 500-ns atomistic molecular dynamics simulation. The model is superb in quality and captures most experimentally derived structural features, at both the secondary structure and the side-chain levels. The model consists of a uniquely interlocking module contributed by the C-terminal regions of all three proteins. The functionally important constriction control domain residues of FtsB and FtsL are located at a fixed vertical position of ∼43-49 Å from the membrane surface. While the periplasmic domains of all three proteins are well-defined and rigid, the single transmembrane helices of each are flexible and their collective twisting and bending contribute to most structural variations, according to principal component analysis. Considering FtsQ only, the protein is more flexible in its free state relative to its complexed state-with the biggest structural changes located at the elbow between the transmembrane helix and the α-domain. The disordered N-terminal domains of FtsQ and FtsL associate with the cytoplasmic surface of the inner membrane instead of freely venturing into the solvent. Contact network analysis highlighted the formation of the interlocking trimeric module in FtsQBL as playing a central role in mediating the overall structure of the complex.
摘要：
FtsQBL是位于细菌分裂体组装中途的重要分子复合物。为了可视化和理解它的结构，以及它的膜锚定的后果，我们使用深度学习预测工具产生了大肠杆菌复合体的模型，AlphaFold2.将异源三聚体模型插入3脂质模型膜中，并进行500ns原子分子动力学模拟。该模型质量极好，捕获了大多数实验得出的结构特征，在二级结构和侧链水平。该模型由所有三种蛋白质的C末端区域贡献的独特互锁模块组成。FtsB和FtsL的功能上重要的收缩控制域残基位于距膜表面约43-49的固定垂直位置。虽然所有三种蛋白质的周质结构域都是明确的和刚性的，每个的单个跨膜螺旋都是柔性的，它们的集体扭曲和弯曲有助于大多数结构变化，根据主成分分析。仅考虑FtsQ，相对于其复合状态，该蛋白质在其自由状态下更灵活-最大的结构变化位于跨膜螺旋和α结构域之间的肘部。FtsQ和FtsL的无序N端结构域与内膜的细胞质表面缔合，而不是自由地进入溶剂。接触网络分析强调了FtsQBL中互锁三聚体模块的形成，在调节复合体的整体结构中起着核心作用。
