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Characterization of a predominant immunogenic outer membrane protein of Riemerella anatipestifer
S Subramaniam1, B Huang, H Loh
1Institute for Veterinary Bacteriology, University of Bern, CH-3012 Bern, Switzerland.
Abstract:
The ompA gene, encoding the 42-kDa major antigenic outer membrane protein OmpA of Riemerella anatipestifer, the etiololgical agent of septicemia anserum exsudativa, was cloned and expressed in Escherichia coli. Recombinant OmpA displayed a molecular mass similar to that predicted from the nucleotide sequence of the ompA gene but lower than that observed in total cell lysates of R. anatipestifer. The ompA gene showed a conserved C-terminal region comprising the OmpA-like domain and a variable N-terminal region. This structure is similar to those of the analogous outer membrane proteins of several gram-negative bacteria. However, OmpA of R. anatipestifer contains six EF-hand calcium-binding domains and two PEST regions, which distinguish it from other outer membrane proteins. The occurrence of these motifs in OmpA suggests a possible role in virulence for this protein. The ompA gene is present in the R. anatipestifer type strain and in all serotype reference strains. However, it exhibits some minor genetic heterogeneity among different serotypes, which seems not to affect the strong antigenic characteristics of the protein. OmpA is a conserved and strong antigenic determinant of R. anatipestifer and hence is suggested to be a valuable protein for the serodetection of R. anatipestifer infections, independent of their serotype.
Insights
The outer membrane protein A (OmpA) of Riemerella anatipestifer is a conserved, highly antigenic protein. Its unique structure suggests a role in virulence and makes it a valuable target for serological detection of R. anatipestifer infections.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Riemerella anatipestifer causes septicemia anserum exsudativa in birds.
- The outer membrane protein A (OmpA) is a major antigen of R. anatipestifer.
- Understanding OmpA's structure and function is crucial for disease control.
Purpose of the Study:
- To clone and express the ompA gene from R. anatipestifer.
- To characterize the recombinant OmpA protein.
- To investigate the potential of OmpA as a diagnostic marker.
Main Methods:
- Cloning and expression of the ompA gene in Escherichia coli.
- Analysis of recombinant OmpA molecular mass and comparison with native OmpA.
- Sequence analysis of the ompA gene to identify conserved and variable regions and functional motifs.
- Detection of the ompA gene across different R. anatipestifer serotypes.
Main Results:
- The ompA gene was successfully cloned and expressed in E. coli, producing recombinant OmpA.
- Recombinant OmpA showed a molecular mass consistent with its predicted sequence.
- The R. anatipestifer OmpA possesses unique features, including EF-hand calcium-binding domains and PEST regions, distinguishing it from other bacterial outer membrane proteins.
- The ompA gene is conserved across various R. anatipestifer serotypes, despite minor genetic variations, maintaining its strong antigenic properties.
Conclusions:
- OmpA of R. anatipestifer is a conserved and highly antigenic protein.
- The unique structural motifs in OmpA suggest a potential role in bacterial virulence.
- OmpA is a promising candidate for the development of serological diagnostic tools for R. anatipestifer infections, applicable across different serotypes.