PROSITE documentation PDOC00886
Fimbrial biogenesis outer membrane usher protein signature


In Gram-negative bacteria the biogenesis of fimbriae (or pili) requires a two-component assembly and transport system which is composed of a periplasmic chaperone (see <PDOC00552>) and an outer membrane protein which has been termed a molecular 'usher' [1,2,3]. The protein is rather large (from 86 to 100 Kd) and seems to be mainly composed of membrane-spanning β-sheets, a structure reminiscent of porins. Known members of this family are listed below:

  • Escherichia coli papC for P pili.
  • Escherichia coli afaC for AFA-III adhesin.
  • Escherichia coli aggC for AAF/I fimbriae.
  • Escherichia coli cssD for CS6 antigen.
  • Escherichia coli faeD for K88 pili.
  • Escherichia coli fanD for K99 pili.
  • Escherichia coli fasD for 987P fimbria.
  • Escherichia coli fimD for type 1 fimbriae.
  • Escherichia coli focD for F1C fimbriae.
  • Escherichia coli htrE for a yet unknown pilin.
  • Escherichia coli CS3-2 for CS3 pili.
  • Bordetella pertussis fhaA (or fimC) for filamentous hemagglutinin and fimbria.
  • Haemophilus influenzae hifC for type b pili.
  • Klebsiella pneumoniae mrkC for type 3 pili.
  • Proteus mirabilis pmfC for PMF fimbriae.
  • Salmonella enteritidis sefC for sef14 fimbriae.
  • Salmonella typhimurium lpfC for long polar fimbriae.
  • Yersinia enterocolitica myfC for myf fimbriae.
  • Yersinia pestis caf1A for F1 capsule antigen.
  • Escherichia coli hypothetical protein ybgQ.
  • Escherichia coli hypothetical protein ycbS.
  • Escherichia coli hypothetical protein yehB.
  • Escherichia coli hypothetical protein yfcU.
  • Escherichia coli hypothetical protein yhcD.
  • Escherichia coli hypothetical protein yqiG.
  • Escherichia coli hypothetical protein yraJ.

The degree of sequence similarity of these proteins is not very high. However they share a number of characteristics. One them is the presence of two pairs of cysteines, the first one is located in the N-terminal part and the second at the C-terminal extremity. They are probably involved in disulfide bonds. The best conserved region is located in the central part of these proteins and can be used as a signature pattern.

Expert(s) to contact by email:

Schifferli D.M.

Last update:

November 1997 / Text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

FIMBRIAL_USHER, PS01151; Fimbrial biogenesis outer membrane usher protein signature  (PATTERN)


1AuthorsJacob-Dubuisson F. Striker R. Hultgren S.J.
SourceJ. Biol. Chem. 269:12447-12455(1994).

2AuthorsSchifferli D.M. Alrutz M.A.
TitlePermissive linker insertion sites in the outer membrane protein of 987P fimbriae of Escherichia coli.
SourceJ. Bacteriol. 176:1099-1110(1994).
PubMed ID7906265

3Authorsvan Rosmalen M. Saier M.H. Jr.
SourceRes. Microbiol. 144:507-527(1993).

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