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Characterization and expression of a novel Porphyromonas gingivalis outer membrane protein, Omp28
N Slakeski1, M Margetts, C Moore
1School of Dental Science, The University of Melbourne, 711 Elizabeth Street, Victoria 3000, Australia.
Abstract:
We report the characterization of a Porphyromonas gingivalis gene, designated omp28, encoding a protein that we have previously purified and characterized as a 28-kDa outer membrane protein. The deduced amino acid sequence of the omp28 open reading frame displayed an outer membrane leader sequence and lipoprotein attachment site but did not exhibit any significant overall sequence identity with protein sequences in the databases. A small stretch of amino acids (19 residues) exhibits 50% sequence identity with a segment of a fimbrial protein from Dichelobacter nodosus involved in adhesion, suggesting that Omp28 may be a surface adhesin/receptor of P. gingivalis. Using the pET-24 vector we expressed recombinant Omp28 (rOmp28) in Escherichia coli. Western blot analyses of purified rOmp28 with rabbit antisera to a P. gingivalis outer membrane preparation, protective rat anti-whole P. gingivalis antisera and pooled human sera from chronic periodontitis patients showed that the recombinant was recognized by all antisera. Further, anti-rOmp28 antisera exhibited strong reactivity with a panel of four laboratory strains and 10 clinical isolates of P. gingivalis from the United States, Sudan, Romania and Norway. These results suggest that Omp28 is expressed by a wide distribution of P. gingivalis strains.
Insights
We characterized the Porphyromonas gingivalis Omp28 protein, a potential adhesin. Recombinant Omp28 was recognized by various antisera, suggesting it is widely expressed across P. gingivalis strains.
Area of Science:
- Microbiology
- Molecular Biology
- Immunology
Background:
- Porphyromonas gingivalis is a key pathogen in chronic periodontitis.
- Outer membrane proteins of P. gingivalis are potential virulence factors and diagnostic targets.
Purpose of the Study:
- To characterize the Porphyromonas gingivalis omp28 gene and its encoded protein.
- To investigate the potential role of Omp28 as a surface adhesin/receptor.
- To determine the expression and distribution of Omp28 in P. gingivalis strains.
Main Methods:
- Gene cloning and expression of recombinant Omp28 (rOmp28) in Escherichia coli.
- Western blot analysis using antisera against P. gingivalis and rOmp28.
- Sequence analysis of the omp28 gene.
Main Results:
- The omp28 gene encodes a 28-kDa outer membrane protein with a leader sequence and lipoprotein attachment site.
- Omp28 shares limited sequence identity with other proteins but has a segment similar to a Dichelobacter nodosus fimbrial protein, suggesting adhesive properties.
- Recombinant Omp28 was recognized by antisera from P. gingivalis-infected animals and humans, as well as by sera from periodontitis patients.
- Anti-rOmp28 antisera reacted strongly with diverse laboratory strains and clinical isolates of P. gingivalis from multiple geographic locations.
Conclusions:
- Omp28 is a surface-exposed protein of P. gingivalis with potential adhesin/receptor functions.
- Omp28 is conserved and widely expressed among different P. gingivalis strains, making it a potential diagnostic marker or vaccine candidate.