Major antigenic determinants of F and ColB2 pili.
F-like conjugative pili are expressed by plasmids with closely related transfer systems. They are tubular filaments that are composed of repeating pilin subunits arranged in a helical array. Both F and ColB2 pilin have nearly identical protein sequences, and both contain an acetylated amino-terminal alanine residue. However, they differ by a few amino acid residues at their amino termini. Rabbit antisera raised against purified F and ColB2 pili are immunologically cross-reactive by only 25%, as measured by a competition enzyme-linked immunosorbent assay (ELISA). A tryptic peptide corresponding to the first 15 amino acid residues of ColB2 pilin was isolated and found to remove nearly 80% of ColB2 pilus-directed rabbit antibodies. The corresponding tryptic peptide from F pilin, which reacted with anti-F pilus antibodies to remove 80%, was less than 20% reactive with anti-ColB2 pilus antiserum. Cleavage of these peptides with cyanogen bromide (at a methionine residue approximately in the middle of the peptide) did not affect the antigenicity of these peptides. Synthetic N alpha-acetylated peptides corresponding to the first eight amino acids of F pilin (Ac-Ala-Gly-Ser-Ser-Gly-Gln-Asp-Leu-COOH) and the first six amino acids of ColB2 pilin (Ac-Ala-Gln-Gly-Gln-Asp-Leu-COOH) were prepared and tested by competition ELISA with homologous and heterologous anti-pilus antisera. The F peptide F(1-8) inhibited the interaction of F pili and anti-F pilus antiserum to 80%, while the ColB2 peptide ColB2(1-6) inhibited anti-ColB2 pilus antiserum reacting with ColB2 pili by greater than 60%. The two peptides F(1-8) and ColB2(1-6) were inactive by competition ELISAs with heterologous antisera. These results suggest that the major antigenic determinant of both F and ColB2 pili is at the amino terminus of the pilin subunit and that 80% of antibodies raised against these pili are specific for this region of the pilin molecule.
B B
BB
Finlay
L S
LS
Frost
W
W
Paranchych
J M
JM
Parker
R S
RS
Hodges
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000032:analysis*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000276:immunology*; D003086:Bacteriocin Plasmids; D003429:Cross Reactions; D000939:Epitopes; D004926:Escherichia coli / Q000276:immunology*; D029968:Escherichia coli Proteins; D005144:F Factor; D036781:Fimbriae Proteins; D010861:Fimbriae, Bacterial / Q000276:immunology*; D009842:Oligopeptides / Q000276:immunology; D013045:Species Specificity
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D000939:Epitopes; D029968:Escherichia coli Proteins; C444040:F pilin, E coli; D009842:Oligopeptides; D036781:Fimbriae Proteins