Outer-membrane PapC molecular usher discriminately recognizes periplasmic chaperone-pilus subunit complexes

K. W. Dodson, F. Jacob-Dubuisson, R. T. Striker, S. J. Hultgren

Research output: Contribution to journalArticle

164 Scopus citations


P pili are highly ordered composite structures consisting of thin fibrillar tips joined end-to-end to rigid helical rods. The production of these virulence-associated structures requires a periplasmic chaperone (PapD) and an outer membrane protein (PapC) that is the prototype member of a newly recognized class of proteins that we have named 'molecular ushers. Two in vitro assays showed that the preassembly complexes that PapD forms with the three most distal tip fibrillar proteins (PapG, PapF, and PapE) bound to PapC. The relative affinity of each complex for PapC was found to correlate with the final position of the subunit type in the tip fibrillum. In contrast, the complexes PapD forms with the major component of the pilus rod, PapA, or the pilus rod initiating protein, PapK, did not recognize PapC. The in vitro data argue that differential targeting of chaperone-subunit complexes to PapC may be part of a mechanism to ensure the correctly ordered assembly of adhesive composite pili.

Original languageEnglish
Pages (from-to)3670-3674
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Jan 1 1993


  • P pili
  • bacterial adhesin
  • pathogenesis
  • postsecretional assembly

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