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The bacterial outer membrane protein that reacts with anti-HLA-B27 antibodies is the OmpA protein
J J Zhang1, M Hamachi, T Hamachi
1Department of Medicine, University of California, Los Angeles 90024-167022.
Abstract:
A bacterial outer membrane protein of 35-kDa Mr has been reported to react with several anti-HLA-B27 mAb. Here, we demonstrated that this protein showed the heat-modifiability of the OmpA protein during SDS-PAGE. Further, the protein was not detected in mutants of Escherichia coli in which the expression of the OmpA protein has been suppressed. The protein would be reexpressed when one of the mutants was transformed with an expression vector carrying the OmpA gene. Finally, the identity of the reactive protein to OmpA protein was verified by homology in amino acid sequences. An NH2-terminal fragment of this protein was generated by tryptic digestion. Inasmuch as this was unreactive with the anti-HLA-B27 antibody, we concluded that the carboxyl-terminus contributed directly or indirectly to the reactive domain.
Insights
Researchers identified a bacterial outer membrane protein that reacts with anti-HLA-B27 monoclonal antibodies. This protein was confirmed to be OmpA, with its carboxyl-terminus being crucial for antibody binding.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- A 35-kDa bacterial outer membrane protein has been shown to react with anti-HLA-B27 monoclonal antibodies (mAbs).
- The precise identity and function of this protein in relation to HLA-B27 reactivity remain unclear.
Purpose of the Study:
- To identify the bacterial outer membrane protein that reacts with anti-HLA-B27 mAbs.
- To elucidate the specific domain of the protein responsible for this reactivity.
Main Methods:
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to assess heat-modifiability.
- Analysis of Escherichia coli mutants with suppressed OmpA expression.
- Complementation of mutants with an OmpA expression vector.
- Amino acid sequence homology analysis.
- Tryptic digestion and fragment analysis.
Main Results:
- The 35-kDa protein exhibited heat-modifiability characteristic of the OmpA protein.
- The protein was absent in Escherichia coli mutants lacking OmpA expression.
- Reintroduction of the OmpA gene restored protein expression.
- Amino acid sequence homology confirmed the protein's identity as OmpA.
- A carboxyl-terminal fragment of OmpA was identified as the reactive domain for anti-HLA-B27 antibodies.
Conclusions:
- The bacterial outer membrane protein reacting with anti-HLA-B27 mAbs is OmpA.
- The carboxyl-terminus of OmpA is essential for its reactivity with anti-HLA-B27 antibodies.
- This finding suggests a potential molecular mimicry or cross-reactivity mechanism involving OmpA and HLA-B27.