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Expression and properties of an aerolysin– Clostridium septicum alpha toxin hybrid protein
Author(s) -
Diep Dzung B.,
Nelson Kim L.,
Lawrence Tracy S.,
Sellman Bret R.,
Tweten Rodney K.,
Buckley J. Thomas
Publication year - 1999
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1999.01217.x
Subject(s) - aerolysin , biology , toxin , aeromonas hydrophila , microbiology and biotechnology , biochemistry , bacteria , genetics
Aerolysin is a bilobal channel‐forming toxin secreted by Aeromonas hydrophila . The alpha toxin produced by Clostridium septicum is homologous to the large lobe of aerolysin. However, it does not contain a region corresponding to the small lobe of the Aeromonas toxin, leading us to ask what the function of the small lobe is. We fused the small lobe of aerolysin to alpha toxin, producing a hybrid protein that should structurally resemble aerolysin. Unlike aerolysin, the hybrid was not secreted when expressed in Aeromonas salmonicida . The purified hybrid was activated by proteolytic processing in the same way as both parent proteins and, after activation, it formed oligomers that corresponded to the aerolysin heptamer. Like aerolysin, the hybrid was far more active than alpha toxin against human erythrocytes and mouse T lymphocytes. Both aerolysin and the hybrid bound to human glycophorin, and both were inhibited by preincubation with this erythrocyte glycoprotein, whereas alpha toxin was unaffected. We conclude that aerolysin contains two receptor binding sites, one for glycosylphosphatidylinositol‐anchored proteins that is located in the large lobe and is also found in alpha toxin, and a second site, located in the small lobe, that binds a surface carbohydrate determinant.