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
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
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.
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