Zavialov Anton V, Tischenko Vladimir M, Fooks Laura J, Brandsdal Bjørn O, Aqvist Johan, Zav'yalov Vladimir P, Macintyre Sheila, Knight Stefan D
Department of Molecular Biology, Uppsala Biomedical Center, Swedish University of Agricultural Sciences, Box 590, SE-753 24 Uppsala, Sweden.
Biochem J. 2005 Aug 1;389(Pt 3):685-94. doi: 10.1042/BJ20050426.
Periplasmic chaperone/usher machineries are used for assembly of filamentous adhesion organelles of Gram-negative pathogens in a process that has been suggested to be driven by folding energy. Structures of mutant chaperone-subunit complexes revealed a final folding transition (condensation of the subunit hydrophobic core) on the release of organelle subunit from the chaperone-subunit pre-assembly complex and incorporation into the final fibre structure. However, in view of the large interface between chaperone and subunit in the pre-assembly complex and the reported stability of this complex, it is difficult to understand how final folding could release sufficient energy to drive assembly. In the present paper, we show the X-ray structure for a native chaperone-fibre complex that, together with thermodynamic data, shows that the final folding step is indeed an essential component of the assembly process. We show that completion of the hydrophobic core and incorporation into the fibre results in an exceptionally stable module, whereas the chaperone-subunit pre-assembly complex is greatly destabilized by the high-energy conformation of the bound subunit. This difference in stabilities creates a free energy potential that drives fibre formation.
周质伴侣/组装分子机器用于革兰氏阴性病原体丝状黏附细胞器的组装，这一过程被认为是由折叠能量驱动的。突变型伴侣-亚基复合物的结构显示，在细胞器亚基从伴侣-亚基预组装复合物释放并整合到最终纤维结构时，发生了最终的折叠转变（亚基疏水核心的凝聚）。然而，鉴于预组装复合物中伴侣和亚基之间的大界面以及该复合物报道的稳定性，很难理解最终折叠如何能释放足够的能量来驱动组装。在本文中，我们展示了天然伴侣-纤维复合物的X射线结构，该结构与热力学数据一起表明，最终折叠步骤确实是组装过程的一个重要组成部分。我们表明，疏水核心的完成和整合到纤维中会产生一个异常稳定的模块，而伴侣-亚基预组装复合物则因结合亚基的高能构象而大大不稳定。这种稳定性差异产生了驱动纤维形成的自由能势。
