Institut Pasteur, Université Paris Cité, CNRS UMR3528, Structural Bioinformatics Unit, 75015 Paris, France.
Institut Pasteur, Université Paris Cité, CNRS UMR3528, Biochemistry of Macromolecular Interactions Unit, 75015 Paris, France.
Structure. 2023 Feb 2;31(2):152-165.e7. doi: 10.1016/j.str.2022.12.003. Epub 2022 Dec 30.
Type II secretion systems (T2SSs) allow diderm bacteria to secrete hydrolytic enzymes, adhesins, or toxins important for growth and virulence. To promote secretion of folded proteins, T2SSs assemble periplasmic filaments called pseudopili or endopili at an inner membrane subcomplex, the assembly platform (AP). Here, we combined biophysical approaches, nuclear magnetic resonance (NMR) and X-ray crystallography, to study the Klebsiella AP components PulL and PulM. We determined the structure and associations of their periplasmic domains and describe the structure of the heterodimer formed by their ferredoxin-like domains. We show how structural complementarity and plasticity favor their association during the secretion process. Cysteine scanning and crosslinking data provided additional constraints to build a structural model of the PulL-PulM assembly in the cellular context. Our structural and functional insights, together with the relative cellular abundance of its components, support the role of AP as a dynamic hub that orchestrates pilus polymerization.
II 型分泌系统（T2SSs）允许双菌毛细菌分泌对生长和毒力很重要的水解酶、黏附素或毒素。为了促进折叠蛋白的分泌，T2SS 在内膜亚基复合物（组装平台，AP）处组装称为假菌毛或内菌毛的周质丝。在这里，我们结合了生物物理方法、核磁共振（NMR）和 X 射线晶体学来研究肺炎克雷伯氏菌的 AP 成分 PulL 和 PulM。我们确定了它们周质结构域的结构和相互作用，并描述了它们铁氧还蛋白样结构域形成的异二聚体的结构。我们展示了结构互补性和可塑性如何在分泌过程中促进它们的相互作用。半胱氨酸扫描和交联数据提供了更多的约束条件，以构建细胞环境中 PulL-PulM 组装的结构模型。我们的结构和功能见解，以及其成分的相对细胞丰度，支持了 AP 作为协调菌毛聚合的动态中心的作用。
