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The blood group antigen binding activity of the Helicobacter pylori baba adhesin is regulated by local ph and redox potential
Department of Odontology/Oral Microbiology, Umeå University, Umeå, Sweden.
Department of Odontology/Oral Microbiology, Umeå University, Umeå, Sweden.
Institute of Medical Biochemistry, Göteborg University, Göteborg, Sweden.
Department of Odontology/Oral Microbiology, Umeå University, Umeå, Sweden.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The blood group antigen hinding adhesin, BabA, which binds to fucosylated blood group antigens, such as the Lewis b (Leb) and H1 antigens constitutes one of the best recognized adhesin-receptor interactions that mediate adherence of Helicobacter pylori to the gastric epithelium. BabA belongs to a family of H. pylori outer membrane, proteins (HOPs), a group of some 30 proteins with most similar N- and C-terminal domains.

We previously identified the babA1 and babA2 genes, where babA2 was found to encode the BabA adhesin in strain CCUG17875. Here, we confirmed the identity of the BabA protein by immunoblot-analysis, followed by MALDIT-OF MS analysis, which also provided molecular weight of the BabA polypeptide and the unique peptide sequences for BabA. Surprisingly, the BabA protein was found to be expressed 50-fold higher compared to the number of calculated bacterial Leb-binding sites.

Furthermore, surface scan of the bacterial membrane by freeze fracture immuno-EM technique localized the BabA by immunogold labeling to the  bacterial surface in numbers similar to the predicted binding sites. To help explain the binding results, crosslinker-analyses were performed which revealed that BabA form supra-molecular complexes on the bacterial surfaces. In addition, binding to the Lewis b antigen was shown to be pH dependent and took place over a broad pH range but binding activity was reversibly lost when approaching pH 3, i.e. conditions similar to the acidic gastric juice.

The binding activity of the BabA adhesin was shown to be sensitive for reducing conditions, which suggests the presence of disulfide bond(s) close to the carbohydrate-binding domain. The dynamics of BabA in Leb-binding suggest that the bacterial adhesin is regulated by local variations in pH and redox potential, such as the pH gradient in the slimy mucus lining of the epithelium, and the reduced conditions of the inflamed gastric mucosa.

National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-84616OAI: oai:DiVA.org:liu-84616DiVA: diva2:560743
Available from: 2012-10-15 Created: 2012-10-15 Last updated: 2012-10-15Bibliographically approved
In thesis
1. Characterisation of surface traits of Helicobacter pylori and their role in the infectious process
Open this publication in new window or tab >>Characterisation of surface traits of Helicobacter pylori and their role in the infectious process
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The surface appendages of bacteria determine the initial contact with host cells. Characterisation of functional organisation and spatial distribution of adhesive traits of outer membrane components of Gram-negative bacteria is a key issue in studies of the parasite-host cell interaction.

With focus on the enteropathogenic Helicobacter pylori, evidenced to cause chronic gastric infections in humans, detergent-digested freeze fracture replica labelling was applied for ultrastructural analyses of envelope distribution of the virulence factors blood group antigen binding adhesin (BabA), and the carbonic anhydrases (α-CA, ß-CA). In a preliminary study the methodology was also used to study the bacteria-host contact between phagocytosing human neutrophils and wild-type H. pylori.

In parallel, bacterial traits were analysed from a molecular and biochemical perspective. This included the specific roles of the BabA and the sialic acid-binding adhesin (SabA), and the neutrophil activating protein (HP-NAP) in neutrophilic stimulation and subsequent inflammatory process. It was concluded that SabA is crucial in the initiation of a neutrophilic response in the mediated inflammation.

This thesis has demonstrated the synergistic application of ultrastructural, molecular and cellular microbiology tools for delineating complex patterns in bacteria-host interactions, thus utilising the well-characterised and clinically important human pathogen H. pylori. This approach could be applicable to other Gram-negative species to clarify known and discern new virulence mechanisms in the multifaceted field of bacterial pathogenesis and bacterial interactions with human host cells.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2003. 77 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 805
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26665 (URN)11231 (Local ID)91-7373-490-X (ISBN)11231 (Archive number)11231 (OAI)
Public defence
2003-10-03, Elsa Brändströmsalen, Hälsouniversitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2012-10-15Bibliographically approved

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Christoffer, PeterssonMagnusson, Karl-Eric

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