Irreversible loss of membrane-binding activity of Listeria-derived cytolysins in non-acidic conditions: a distinct difference from allied cytolysins produced by other Gram-positive bacteria.
Listeriolysin O (LLO), a member of the cholesterol-dependent cytolysin (CDC) family, is a major virulence factor of Listeria monocytogenes and contributes to bacterial escape from intracellular killing of macrophages. LLO is activated under weakly acidic conditions; however, the molecular mechanism of this pH-dependent expression of cytolytic activity of LLO is poorly understood. In this study, CDCs including LLO, ivanolysin O (ILO), seeligeriolysin O (LSO), pneumolysin (PLY), streptolysin O (SLO) and perfringolysin O (PFO) were prepared as recombinant proteins and examined for their functional changes after treatment under various pH conditions. Haemolytic and membrane cholesterol-binding activities were not affected in PLY, SLO and PFO at any pH examined. By contrast, all the Listeria-derived cytolysins, LLO, ILO and LSO, were active only at an acidic pH and rapidly inactivated under neutral or alkaline conditions. Once inactivated, LLO could not be reactivated even by a downward pH shift. The hydrophobicity of LLO treated at neutral or alkaline pH was increased. These data suggested that the pH-dependent loss of cytolytic activity appeared to be due to irreversible structural changes of domain 4 that resulted in the loss of target membrane cholesterol binding.
Nomura
Takamasa
T
Department of Microbiology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
Kawamura
Ikuo
I
Department of Microbiology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
Kohda
Chikara
C
Department of Microbiology and Immunology, Showa University School of Medicine, Tokyo 142-8555, Japan.
Baba
Hisashi
H
Department of Infectious Diseases, Nagoya University School of Medicine, Nagoya 466-8550, Japan.
Ito
Yutaka
Y
Department of Respiratory Medicine, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.|Department of Microbiology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
Kimoto
Terumi
T
Department of Microbiology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
Watanabe
Isao
I
Department of Microbiology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
Mitsuyama
Masao
M
Department of Microbiology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan.
D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D003603:Cytotoxins / Q000276:immunology / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000502:physiology; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000378:metabolism* / Q000472:pathogenicity
D001427:Bacterial Toxins; D003603:Cytotoxins; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; D002784:Cholesterol; C038705:hlyA protein, Listeria monocytogenes