title: Assembly proteins of CS1 pili of enterotoxigenic Escherichia coli.
abstract: Some strains of enterotoxigenic Escherichia coli associated with human diarrhoeal disease produce a class of pili represented by those called CS1. For the assembly of the major-pilin subunit, CooA, into pili, each of four linked genes, cooB, A, C, and D, is required. In this study, we have determined the subcellular localization of CooB, C and D, and investigated the molecular interactions of these proteins using specific antisera. CooD appears to be an integral pilus protein because it co-purifies with, and is strongly associated with, CS1 pili. In keeping with its role as an assembly protein, the CooD minor pilin (when overexpressed in CS1-piliated strains) was detected in periplasmic intermolecular complexes with the major-pilin subunit CooA. CooB is an assembly protein found exclusively in the periplasm of CS1-piliated strains. CooB also forms periplasmic intermolecular complexes with CooA, but does not constitute part of the final pilus structure. Immunoblot analysis of cell fractions showed that CooC is an outer membrane protein of CS1-piliated E. coli. Based on this information, we have proposed a model for CS1-pilus assembly which is very similar to the model for polymerization of the PapA pilin of uropathogenic E. coli. As the assembly proteins of Pap and CS1 pili are structurally unrelated, this may represent a case of convergent evolution.
authors.affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: H
authors.initials: H
authors.lastname: Sakellaris
authors.forename: D P
authors.initials: DP
authors.lastname: Balding
authors.forename: J R
authors.initials: JR
authors.lastname: Scott
mesh_terms: D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004768:Enterotoxins; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity / Q000502:physiology; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000502:physiology*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C088904:CooA protein, E coli; C088906:CooC protein, E coli; C088905:CooD protein, E coli; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D036781:Fimbriae Proteins