Structural and biochemical analysis of Sec translocon machinery

蛋白质跨膜转运是所有生物体中基本和必需的细胞活动之一。我们解决了膜组件SecDF的第一个3D结构，它在细菌中新合成的蛋白质跨膜的有效转运中起着重要作用。从结构特征和功能分析，我们提出SecDF作为膜整合的伴侣蛋白发挥作用，其驱动蛋白质的运动而不使用能量的主要货币ATP，但具有显著的构象变化周期，由质子H+离子）梯度跨膜提供动力。我们的SecDF功能模型已经通过一系列的生物化学和生物物理学方法进行了验证。这项研究揭示了一种新的原子级原理，特别是细胞蛋白质递送系统和一般主动运输的生物学机制，细胞不仅获得或处理大分子，还获得或处理离子，药物和营养物质。

Transport of proteins across membranes is one of the fundamental and essential cellular activities in all organisms. We solved the first 3D structure of a membrane component SecDF, which plays an important role in efficient translocation of newly synthesized proteins across the membrane in bacteria. From the structural features and functional analyses, we proposed that SecDF functions as a membrane-integrated chaperone, which drives movement of proteins without using a major currency, ATP, of energy, but with remarkable cycles of conformational changes, powered by a proton H+ion) gradient across the membrane. Our model of the SecDF function has been verified by a series of biochemical and biophysical approaches. This research uncovers a new, atomic-level principle that underlies the cellular protein delivery systems in particular and biological mechanisms of active transport in general, by which cells acquire or dispose not only macromolecules but also ions, drugs and nutrients.