Department of Biomedical Engineering, McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA; Center for Science & Engineering of Living Systems (CSELS), McKelvey School of Engineering, Washington University in St. Louis St. Louis, MO 63130, USA.
Center for Science & Engineering of Living Systems (CSELS), McKelvey School of Engineering, Washington University in St. Louis St. Louis, MO 63130, USA; Department of Biology, Washington University in St. Louis St. Louis, MO 63130, USA.
J Mol Biol. 2020 May 1;432(10):3205-3221. doi: 10.1016/j.jmb.2020.03.008. Epub 2020 Mar 18.
FtsZ is a bacterial GTPase that is central to the spatial and temporal control of cell division. It is a filament-forming enzyme that encompasses a well-folded core domain and a disordered C-terminal tail (CTT). The CTT is essential for ensuring proper assembly of the cytokinetic ring, and its deletion leads to mis-localization of FtsZ, aberrant assembly, and cell death. In this work, we dissect the contributions of modules within the disordered CTT to assembly and enzymatic activity of Bacillus subtilis FtsZ (Bs-FtsZ). The CTT features a hypervariable C-terminal linker (CTL) and a conserved C-terminal peptide (CTP). Our in vitro studies show that the CTL weakens the driving forces for forming single-stranded active polymers and suppresses lateral associations of these polymers, whereas the CTP promotes the formation of alternative assemblies. Accordingly, in full-length Bs-FtsZ, the CTL acts as a spacer that spatially separates the CTP sticker from the core, thus ensuring filament formation through core-driven polymerization and lateral associations through CTP-mediated interactions. We also find that the CTL weakens GTP binding while enhancing the catalytic rate, whereas the CTP has opposite effects. The joint contributions of the CTL and CTP make Bs-FtsZ, an enzyme that is only half as efficient as a truncated version that lacks the CTT. Overall, our data suggest that the CTT acts as an auto-regulator of Bs-FtsZ assembly and as an auto-inhibitor of enzymatic activity. Based on our results, we propose hypotheses regarding the hypervariability of CTLs and compare FtsZs to other bacterial proteins with tethered IDRs.
FtsZ 是一种细菌 GTPase，它是细胞分裂时空控制的核心。它是一种纤维形成酶，包含一个折叠良好的核心结构域和一个无规卷曲的 C 端尾部（CTT）。CTT 对于确保细胞分裂环的正确组装至关重要，其缺失会导致 FtsZ 定位错误、组装异常和细胞死亡。在这项工作中，我们剖析了无规卷曲 CTT 内的模块对枯草芽孢杆菌 FtsZ（Bs-FtsZ）组装和酶活性的贡献。CTT 具有一个高度可变的 C 端连接子（CTL）和一个保守的 C 端肽（CTP）。我们的体外研究表明，CTL 削弱了形成单链活性聚合物的驱动力，并抑制了这些聚合物的侧向缔合，而 CTP 则促进了替代组装的形成。因此，在全长 Bs-FtsZ 中，CTL 充当间隔物，将 CTP 标签从核心结构域空间上分隔开，从而确保通过核心驱动聚合和 CTP 介导的相互作用进行纤维形成。我们还发现，CTL 削弱了 GTP 结合，同时提高了催化速率，而 CTP 则有相反的作用。CTL 和 CTP 的共同作用使 Bs-FtsZ 成为一种酶，其效率仅为缺乏 CTT 的截断版本的一半。总的来说，我们的数据表明，CTT 作为 Bs-FtsZ 组装的自动调节剂和酶活性的自动抑制剂发挥作用。基于我们的结果，我们提出了关于 CTL 高度变异性的假设，并将 FtsZs 与其他具有连接 IDR 的细菌蛋白进行了比较。
