Identification of Porphyromonas gingivalis proteins secreted by the Por secretion system

Authors

  • Keiko Sato,

    1. Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
    Search for more papers by this author
  • Hideharu Yukitake,

    1. Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
    Search for more papers by this author
  • Yuka Narita,

    1. Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
    Search for more papers by this author
  • Mikio Shoji,

    1. Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
    Search for more papers by this author
  • Mariko Naito,

    1. Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
    Search for more papers by this author
  • Koji Nakayama

    Corresponding author
    • Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
    Search for more papers by this author

Correspondence: Koji Nakayama, Division of Microbiology and Oral Infection, Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8588, Japan. Tel.: +81 95 819 7648; fax: +81 95 819 7650; e-mail: knak@nagasaki-u.ac.jp

Abstract

The Gram-negative bacterium Porphyromonas gingivalis possesses a number of potential virulence factors for periodontopathogenicity. In particular, cysteine proteinases named gingipains are of interest given their abilities to degrade host proteins and process other virulence factors such as fimbriae. Gingipains are translocated on the cell surface or into the extracellular milieu by the Por secretion system (PorSS), which consists of a number of membrane or periplasmic proteins including PorK, PorL, PorM, PorN, PorO, PorP, PorQ, PorT, PorU, PorV (PG27, LptO), PorW and Sov. To identify proteins other than gingipains secreted by the PorSS, we compared the proteomes of P. gingivalis strains kgp rgpA rgpB (PorSS-proficient strain) and kgp rgpA rgpB porK (PorSS-deficient strain) using two-dimensional gel electrophoresis and peptide-mass fingerprinting. Sixteen spots representing 10 different proteins were present in the particle-free culture supernatant of the PorSS-proficient strain but were absent or faint in that of the PorSS-deficient strain. These identified proteins possessed the C-terminal domains (CTDs), which had been suggested to form the CTD protein family. These results indicate that the PorSS is used for secretion of a number of proteins other than gingipains and that the CTDs of the proteins are associated with the PorSS-dependent secretion.

Ancillary