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Functional substitution of the TibC protein of enterotoxigenic Escherichia coli strains for the autotransporter adhesin heptosyltransferase of the AIDA system.

ABSTRACT: The plasmid-encoded AIDA (adhesin involved in diffuse adherence) autotransporter protein derived from diffuse-adhering clinical Escherichia coli isolate 2787 and the TibA (enterotoxigenic invasion locus B) protein encoded by the chromosomal tib locus of enterotoxigenic E. coli (ETEC) strain H10407 are posttranslationally modified by carbohydrate substituents. Analysis of the AIDA-I adhesin showed that the modification involved heptose residues. AIDA-I is modified by the heptosyltransferase activity of the product of the aah gene, which is located directly upstream of adhesin-encoding gene aidA. The carbohydrate modification of the TibA adhesin/invasin is mediated by the TibC protein but has not been elucidated. Based on the sequence similarities between TibC and AAH (autotransporter adhesin heptosyltransferase) and between the TibA and the AIDA proteins we hypothesized that the AIDA system and the Tib system encoded by the tib locus are structurally and functionally related. Here we show that (i) TibC proteins derived from different ETEC strains appear to be highly conserved, (ii) recombinant TibC proteins can substitute for the AAH heptosyltransferase in introducing the heptosyl modification to AIDA-I, (iii) this modification is functional in restoring the adhesive function of AIDA-I, (iv) a single amino acid substitution at position 358 completely abolishes this activity, and (v) antibodies directed at the functionally active AIDA-I recognize a protein resembling modified TibA in ETEC strains. In summary, we conclude that, like AAH, TibC represents an example of a novel class of heptosyltransferases specifically transferring heptose residues onto multiple sites of a protein backbone. A potential consensus sequence for the modification site is suggested.

SUBMITTER: Moormann C

PROVIDER: S-EPMC127912 | biostudies-literature | 2002 May

REPOSITORIES: biostudies-literature

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Functional substitution of the TibC protein of enterotoxigenic Escherichia coli strains for the autotransporter adhesin heptosyltransferase of the AIDA system.

Moormann Corinna C Benz Inga I Schmidt M Alexander MA

Infection and immunity 20020501 5

The plasmid-encoded AIDA (adhesin involved in diffuse adherence) autotransporter protein derived from diffuse-adhering clinical Escherichia coli isolate 2787 and the TibA (enterotoxigenic invasion locus B) protein encoded by the chromosomal tib locus of enterotoxigenic E. coli (ETEC) strain H10407 are posttranslationally modified by carbohydrate substituents. Analysis of the AIDA-I adhesin showed that the modification involved heptose residues. AIDA-I is modified by the heptosyltransferase activ ...[more]

PMID: 11953358

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Project description:Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in developing countries, where it accounts for millions of infections and hundreds of thousands of deaths annually. While vaccine development to prevent diarrheal illness due to ETEC is feasible, extensive effort is needed to identify conserved antigenic targets. Pathogenic Escherichia coli, including ETEC, use the autotransporter (AT) secretion mechanism to export virulence factors. AT proteins are comprised of a highly conserved carboxy terminal outer membrane beta barrel and a surface-exposed amino terminal passenger domain. Recent immunoproteomic studies suggesting that multiple autotransporter passenger domains are recognized during ETEC infection prompted the present studies.Available ETEC genomes were examined to identify AT coding sequences present in pathogenic isolates, but not in the commensal E. coli HS strain. Passenger domains of the corresponding autotransporters were cloned and expressed as recombinant antigens, and the immune response to these proteins was then examined using convalescent sera from patients and experimentally infected mice.Potential AT genes shared by ETEC strains, but absent in the E. coli commensal HS strain were identified. Recombinant passenger domains derived from autotransporters, including Ag43 and an AT designated pAT, were recognized by antibodies from mice following intestinal challenge with H10407, and both Ag43 and pAT were identified on the surface of ETEC by flow cytometry. Likewise, convalescent sera from patients with ETEC diarrhea recognized Ag43 and pAT, suggesting that these proteins are expressed during both experimental and naturally occurring ETEC infections and that they are immunogenic. Vaccination of mice with recombinant passenger domains from either pAT or Ag43 afforded protection against intestinal colonization with ETEC.Passenger domains of conserved autotransporter proteins could contribute to protective immune responses that develop following infection with ETEC, and these antigens consequently represent potential targets to explore in vaccine development.

Dataset Information

Functional substitution of the TibC protein of enterotoxigenic Escherichia coli strains for the autotransporter adhesin heptosyltransferase of the AIDA system.

Publications

Functional substitution of the TibC protein of enterotoxigenic Escherichia coli strains for the autotransporter adhesin heptosyltransferase of the AIDA system.

Similar Datasets

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