crystal structure of the p pilus rod subunit papa晶体结构的p纤毛杆单元爸爸.pdfVIP

Crystal Structure of the P Pilus Rod Subunit PapA 1 2* 3* 1* Denis Verger , Esther Bullitt , Scott J. Hultgren , Gabriel Waksman 1 Institute of Structural Molecular Biology, University College London and Birkbeck College, London, United Kingdom, 2 Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America, 3 Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America P pili are important adhesive fibres involved in kidney infection by uropathogenic Escherichia coli strains. P pili are assembled by the conserved chaperone–usher pathway, which involves the PapD chaperone and the PapC usher. During pilus assembly, subunits are incorporated into the growing fiber via the donor–strand exchange (DSE) mechanism, whereby the chaperone’s G1 b-strand that complements the incomplete immunoglobulin-fold of each subunit is displaced by the N-terminal extension (Nte) of an incoming subunit. P pili comprise a helical rod, a tip fibrillum, and an adhesin at the distal end. PapA is the rod subunit and is assembled into a superhelical right-handed structure. Here, we have solved the structure of a ternary complex of PapD bound to PapA through donor–strand complementation, itself bound to another PapA subunit through DSE. This structure provides insight into the structural basis of the DSE reaction involving this important pilus subunit. Using gel filtration chromatography and electron microscopy on a number of PapA Nte mutants, we establish that PapA differs in its mode of assembly compared with other Pap subunits, in