Department of Pathology and Immunology, Washington University School of Medicine, Saint Louis, Missouri 63110, USA.
J Bacteriol. 2010 Apr;192(7):1824-31. doi: 10.1128/JB.01677-09. Epub 2010 Jan 29.
P pili are extracellular appendages responsible for the targeting of uropathogenic Escherichia coli to the kidney. They are assembled by the chaperone-usher (CU) pathway of pilus biogenesis involving two proteins, the periplasmic chaperone PapD and the outer membrane assembly platform, PapC. Many aspects of the structural biology of the Pap CU pathway have been elucidated, except for the C-terminal domain of the PapC usher, the structure of which is unknown. In this report, we identify a stable and folded fragment of the C-terminal region of the PapC usher and determine its structure using both X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. These structures reveal a beta-sandwich fold very similar to that of the plug domain, a domain of PapC obstructing its translocation domain. This structural similarity suggests similar functions in usher-mediated pilus biogenesis, playing out at different stages of the process. This structure paves the way for further functional analysis targeting surfaces common to both the plug and the C-terminal domain of PapC.
菌毛是负责将尿路致病性大肠杆菌靶向肾脏的细胞外附属物。它们由菌毛生物发生的伴侣-usher (CU)途径组装，涉及两种蛋白质，周质伴侣 PapD 和外膜组装平台 PapC。除了 PapC usher 的 C 末端结构域的结构未知外，Pap CU 途径的结构生物学的许多方面都已经阐明。在本报告中，我们鉴定了 PapC usher 的 C 末端区域的稳定和折叠片段，并使用 X 射线晶体学和核磁共振（NMR）光谱法确定了其结构。这些结构揭示了一个非常类似于塞子结构域的β-三明治折叠，塞子结构域是 PapC 的一个阻碍其易位结构域的结构域。这种结构相似性表明在 usher 介导的菌毛生物发生中具有相似的功能，在该过程的不同阶段发挥作用。该结构为针对 PapC 的塞子和 C 末端结构域都共有的表面进行进一步的功能分析铺平了道路。
