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Updated: May 29, 2026
Porphyromonas gingivalis as a Model Organism for Assessing Interaction of Anaerobic Bacteria with Host Cells
Published on: December 17, 2015
Analysis of Porphyromonas gingivalis PG27 by deletion and intragenic suppressor mutation analyses
I Ishiguro1, K Saiki, K Konishi
1Department of Microbiology, Nippon Dental University School of Life Dentistry at Tokyo, Tokyo, Japan.
Abstract:
PG27 is required for secretion of virulence factor gingipains, and has recently been proposed as LptO, which is involved in O-deacylation of lipopolysaccharide. In the present study, a predicted 14 anti-parallel β-strand structure of PG27 was ascertained. Deletion study showed that the region from Asp382 to the C-terminal His391 of PG27 is dispensable for the function of PG27. Analysis of C-terminal deletion mutants revealed that the region in strand S14 (Asn369-Gly385) is important for activity. Of the gingipain-defective mutants, ΔThr378-His391 and ΔPhe377-His391 produced amounts of PG27 comparable to those produced by wild-type cells, suggesting that Thr378-Phe381 contains essential residues for the function of PG27. In contrast, ΔPhe381-His391, ΔAla380-His391, ΔLeu379-His391 and ΔArg376-His391 produced no detectable PG27. The defects of the ΔAla380-His391 mutant were suppressed by changing either Ala346 or Ala359 of PG27 to valine. Importantly, Ala346 and Ala359 are located close to Leu379 in the structural model of PG27. A359V compensated for the instability of PG27, but not the gingipain-defective phenotypes, of other deletion mutants tested, suggesting that Ala380 and Phe381 of PG27 are important for the stability of PG27. Lastly, we found that the C-terminal region of PG27 may be located in the periplasm. Taken together, these findings fit well with a predicted β-barrel structure model for PG27, and show that strand S14 is important for its function.
Insights
The study confirms PG27’s beta-barrel structure and identifies key residues in strand S14 essential for its function in secreting gingipains and potentially O-deacylation of lipopolysaccharide.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- PG27 is crucial for secreting the virulence factor gingipains.
- PG27 has been proposed to function as LptO, involved in lipopolysaccharide O-deacylation.
Purpose of the Study:
- To elucidate the structure and function of PG27.
- To identify specific regions and residues critical for PG27 activity.
Main Methods:
- Structural prediction and ascertainment of PG27's beta-strand structure.
- Deletion studies on PG27 mutants to assess functional impact.
- Site-directed mutagenesis to investigate residue importance.
Main Results:
- The 14 anti-parallel beta-strand structure of PG27 was confirmed.
- Strand S14 (Asn369-Gly385) was identified as vital for PG27 activity.
- Residues Thr378-Phe381 were found essential for gingipain secretion, with Ala380 and Phe381 critical for PG27 stability.
Conclusions:
- PG27 possesses a beta-barrel structure with strand S14 playing a key role in its function.
- Specific C-terminal residues are critical for PG27's enzymatic activity and stability.
- The C-terminal region of PG27 is likely located in the periplasm.
