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Gene Review

pfoA  -  perfringolysin O

Clostridium perfringens str. 13

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Disease relevance of pfoA

  • Perfringolysin O (PFO), a soluble toxin secreted by the pathogenic Clostridium perfringens, forms large homo-oligomeric pore complexes comprising up to 50 PFO molecules in cholesterol-containing membranes [1].
  • Moreover, the expression of the pfoA gene in the luxS mutant was apparently activated when the mutant cells were cultured in the presence of culture supernatants from the wild-type C. perfringens, Escherichia coli DH5alpha carrying the luxS gene of C. perfringens [2].
  • At all temperatures aggregation of PFO was virtually complete before the onset of hemolysis, the latter exhibiting a distinct lag phase [3].
  • PFO-mediated toxicity renders the infected host cell permeable to gentamicin and leads to the death of the intracellular bacteria [4].
  • Synergistic effects of alpha-toxin and perfringolysin O in Clostridium perfringens-mediated gas gangrene [5].

High impact information on pfoA

  • Perfringolysin O (PFO), a water-soluble monomeric cytolysin secreted by pathogenic Clostridium perfringens, oligomerizes and forms large pores upon encountering cholesterol-containing membranes [6].
  • Thus, a limited interaction of D4 with the bilayer core seems to be sufficient to accomplish cholesterol recognition and initial binding of PFO to the membrane [7].
  • These results suggest that the aggregation of membrane-associated PFO is necessary to initiate the hemolytic process, and the lag phase which occurs before onset of hemolysis reflects the kinetics of PFO monomer to polymer conversion [3].
  • PFO was labeled with the isothiocyanate derivatives of either fluorescein or tetramethylrhodamine [3].
  • The VR-RNA promoter identified by primer extension analysis was preceded by a probable VirR-binding site (CCAGTTNNNCAC), which resembled a repeated sequence motif present in the promoter region of the theta-toxin (pfoA) gene [8].

Chemical compound and disease context of pfoA

  • theta-Toxin (perfringolysin O), secreted by Clostridium perfringens, shares with other known thiol-activated toxins a conserved undecapeptide, ECTGLAWEWWR, located in the C-terminal region of the protein and containing the unique cysteine of the molecule [9].

Biological context of pfoA

  • The subsequent strain was complemented with separate plasmids that carried the alpha-toxin structural gene (plc), the perfringolysin O gene (pfoA), or both toxin genes, and the resultant isogenic strains were examined in a mouse myonecrosis model [5].
  • Stimulation was still observed with a 3.9-kb fragment, but stimulation was not observed with fragments that were 3.6 kb or less long, indicating that the upstream region between 3.9 and 1.7 kb was involved in activation of pfoA gene expression [10].
  • For this study, we introduced mutated VirR boxes into a C. perfringens pfoA mutant and found that both VirR boxes are essential for transcriptional activation [11].
  • The VirR response regulator from Clostridium perfringens binds independently to two imperfect direct repeats located upstream of the pfoA promoter [12].
  • A chromosomal DNA library constructed from strain 13 was transformed into strain SI112 to identify the regulatory gene(s) for the pfoA gene [13].

Anatomical context of pfoA

  • Three classes of PFO mutations were identified, all capable of mediating lysis of the vacuole but without a toxic effect upon the infected host cell [4].
  • Acquisition of single amino acid changes in PFO were sufficient to convert an extracellular cytolysin into a vacuole-specific lysin which mediated growth of L. monocytogenes in cultured cells [4].
  • PFO was shown to be the primary mediator of C. perfringens-dependent cytotoxicity to macrophages [14].
  • Effects of Clostridium perfringens alpha-toxin (PLC) and perfringolysin O (PFO) on cytotoxicity to macrophages, on escape from the phagosomes of macrophages, and on persistence of C. perfringens in host tissues [14].
  • C. perfringens survival in the presence of mouse peritoneal macrophages was dependent on both PFO and PLC [14].

Associations of pfoA with chemical compounds


Regulatory relationships of pfoA

  • These results indicate that pfoR positively controls expression of the pfoA gene [10].

Other interactions of pfoA

  • The other gene, hyp7, whose transcript was positively regulated by the VirR/VirS system, was shown to activate the transcription of the colA (kappa-toxin) and plc (alpha-toxin) genes, but not the pfoA (theta-toxin) gene in C. perfringens [17].
  • In an attempt to confirm this hypothesis in C. perfringens, a pfoR-pfoA deletion mutant was complemented with isogenic pfoA(+) shuttle plasmids that varied only in their ability to encode an intact pfoR gene [18].
  • The theta-toxin structural gene, pfoA, had both a major and a very minor promoter, with the major promoter being virR/virS dependent [19].
  • Sequence analysis of flanking regions of the pfoA gene of Clostridium perfringens: beta-galactosidase gene (pbg) is located in the 3'-flanking region [20].

Analytical, diagnostic and therapeutic context of pfoA

  • When late-log-phase vegetative culture supernatants were analyzed by quantitative Western blotting or activity assays, most type C isolates produced at least three lethal toxins, alpha toxin, beta toxin, and perfringolysin O, and several isolates also produced beta2 toxin [21].
  • The structure of the monomeric form of perfringolysin O solved by X-ray crystallography has been used to model the very large transmembrane pore formed when this bacterial protein toxin assembles in cholesterol-containing membranes [22].
  • Purification of the pfo product was accomplished by high-resolution gel filtration and anion-exchange chromatography [15].
  • Cereolysin, streptolysin O, and perfringolysin O formed precipitin lines that completely fused when reacted with horse antitetanolysin by Ouchterlony immunodiffusion and formed precipitin lines that showed either partial or complete fusion when diffused against horse antistreptolysin O or antiperfringolysin O [23].
  • Cryo-electron microscopy and image analysis of the helical arrays were used to reconstruct a 3D density map of wild-type PFO [24].


  1. Prepore to pore transition of a cholesterol-dependent cytolysin visualized by electron microscopy. Dang, T.X., Hotze, E.M., Rouiller, I., Tweten, R.K., Wilson-Kubalek, E.M. J. Struct. Biol. (2005) [Pubmed]
  2. The luxS gene is involved in cell-cell signalling for toxin production in Clostridium perfringens. Ohtani, K., Hayashi, H., Shimizu, T. Mol. Microbiol. (2002) [Pubmed]
  3. Kinetic aspects of the aggregation of Clostridium perfringens theta-toxin on erythrocyte membranes. A fluorescence energy transfer study. Harris, R.W., Sims, P.J., Tweten, R.K. J. Biol. Chem. (1991) [Pubmed]
  4. Conversion of an extracellular cytolysin into a phagosome-specific lysin which supports the growth of an intracellular pathogen. Jones, S., Preiter, K., Portnoy, D.A. Mol. Microbiol. (1996) [Pubmed]
  5. Synergistic effects of alpha-toxin and perfringolysin O in Clostridium perfringens-mediated gas gangrene. Awad, M.M., Ellemor, D.M., Boyd, R.L., Emmins, J.J., Rood, J.I. Infect. Immun. (2001) [Pubmed]
  6. The mechanism of membrane insertion for a cholesterol-dependent cytolysin: a novel paradigm for pore-forming toxins. Shatursky, O., Heuck, A.P., Shepard, L.A., Rossjohn, J., Parker, M.W., Johnson, A.E., Tweten, R.K. Cell (1999) [Pubmed]
  7. Structural insights into the membrane-anchoring mechanism of a cholesterol-dependent cytolysin. Ramachandran, R., Heuck, A.P., Tweten, R.K., Johnson, A.E. Nat. Struct. Biol. (2002) [Pubmed]
  8. Clostridial VirR/VirS regulon involves a regulatory RNA molecule for expression of toxins. Shimizu, T., Yaguchi, H., Ohtani, K., Banu, S., Hayashi, H. Mol. Microbiol. (2002) [Pubmed]
  9. Contribution of individual tryptophan residues to the structure and activity of theta-toxin (perfringolysin O), a cholesterol-binding cytolysin. Sekino-Suzuki, N., Nakamura, M., Mitsui, K.I., Ohno-Iwashita, Y. Eur. J. Biochem. (1996) [Pubmed]
  10. An upstream regulatory sequence stimulates expression of the perfringolysin O gene of Clostridium perfringens. Shimizu, T., Okabe, A., Minami, J., Hayashi, H. Infect. Immun. (1991) [Pubmed]
  11. The spatial organization of the VirR boxes is critical for VirR-mediated expression of the perfringolysin O gene, pfoA, from Clostridium perfringens. Cheung, J.K., Dupuy, B., Deveson, D.S., Rood, J.I. J. Bacteriol. (2004) [Pubmed]
  12. The VirR response regulator from Clostridium perfringens binds independently to two imperfect direct repeats located upstream of the pfoA promoter. Cheung, J.K., Rood, J.I. J. Bacteriol. (2000) [Pubmed]
  13. The virR gene, a member of a class of two-component response regulators, regulates the production of perfringolysin O, collagenase, and hemagglutinin in Clostridium perfringens. Shimizu, T., Ba-Thein, W., Tamaki, M., Hayashi, H. J. Bacteriol. (1994) [Pubmed]
  14. Effects of Clostridium perfringens alpha-toxin (PLC) and perfringolysin O (PFO) on cytotoxicity to macrophages, on escape from the phagosomes of macrophages, and on persistence of C. perfringens in host tissues. O'Brien, D.K., Melville, S.B. Infect. Immun. (2004) [Pubmed]
  15. Cloning and expression in Escherichia coli of the perfringolysin O (theta-toxin) gene from Clostridium perfringens and characterization of the gene product. Tweten, R.K. Infect. Immun. (1988) [Pubmed]
  16. Activation of phosphatidic acid metabolism of human erythrocyte membranes by perfringolysin O. Saito, M., Ando, S., Mitsui, K., Homma, Y., Takenawa, T. Biochem. Biophys. Res. Commun. (1986) [Pubmed]
  17. Identification of novel VirR/VirS-regulated genes in Clostridium perfringens. Banu, S., Ohtani, K., Yaguchi, H., Swe, T., Cole, S.T., Hayashi, H., Shimizu, T. Mol. Microbiol. (2000) [Pubmed]
  18. Perfringolysin O expression in Clostridium perfringens is independent of the upstream pfoR gene. Awad, M.M., Rood, J.I. J. Bacteriol. (2002) [Pubmed]
  19. The virR/virS locus regulates the transcription of genes encoding extracellular toxin production in Clostridium perfringens. Ba-Thein, W., Lyristis, M., Ohtani, K., Nisbet, I.T., Hayashi, H., Rood, J.I., Shimizu, T. J. Bacteriol. (1996) [Pubmed]
  20. Sequence analysis of flanking regions of the pfoA gene of Clostridium perfringens: beta-galactosidase gene (pbg) is located in the 3'-flanking region. Shimizu, T., Kobayashi, T., Ba-Thein, W., Ohtani, K., Hayashi, H. Microbiol. Immunol. (1995) [Pubmed]
  21. Dissecting the contributions of Clostridium perfringens type C toxins to lethality in the mouse intravenous injection model. Fisher, D.J., Fernandez-Miyakawa, M.E., Sayeed, S., Poon, R., Adams, V., Rood, J.I., Uzal, F.A., McClane, B.A. Infect. Immun. (2006) [Pubmed]
  22. Toxin structure: part of a hole? Bayley, H. Curr. Biol. (1997) [Pubmed]
  23. Antigenic relationships among thiol-activated cytolysins. Cowell, J.L., Bernheimer, A.W. Infect. Immun. (1977) [Pubmed]
  24. Helical crystallization on nickel-lipid nanotubes: perfringolysin O as a model protein. Dang, T.X., Milligan, R.A., Tweten, R.K., Wilson-Kubalek, E.M. J. Struct. Biol. (2005) [Pubmed]
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