Vigneux Fabienne, Zumbihl Robert, Jubelin Grégory, Ribeiro Carlos, Poncet Joël, Baghdiguian Stephen, Givaudan Alain, Brehélin Michel
Ecologie Microbienne des Insectes et Interactions Hôte-Pathogène, Unité Mixte de Recherche 1133, Institut National de la Recherche Agronomique-Université de Montpellier II, 34095 Montpellier, France.
Unité Mixte de Recherche CNRS 5203, INSERM U661, Université de Montpellier I et II, 34094 Montpellier, France.
J Biol Chem. 2007 Mar 30;282(13):9571-9580. doi: 10.1074/jbc.M604301200. Epub 2007 Jan 17.
Xenorhabdus nematophila, a member of the Enterobacteriaceae, kills many species of insects by strongly depressing the immune system and colonizing the entire body. A peptide cytotoxin has been purified from X. nematophila broth growth, and the cytolytic effect on insect immunocytes and hemolytic effect on mammalian red blood cells of this toxin have been described (Ribeiro, C., Vignes, M., and Brehélin, M. (2003) J. Biol. Chem. 278, 3030-3039). We show here that this toxin, Xenorhabdus alpha-xenorhabdolysin (Xax), triggers apoptosis in both insect and mammalian cells. We also report the cloning and sequencing of two genes, xaxAB, encoding this toxin in X. nematophila. The expression of both genes in recombinant Escherichia coli led to the production of active cytotoxin/hemolysin. However, hemolytic activity was observed only if the two peptides were added in the appropriate order. Furthermore, we report here that inactivation of xaxAB genes in X. nematophila abolished the major cytotoxic activity present in broth growth, called C1. We also show that these genes are present in various entomopathogenic bacteria of the genera Xenorhabdus and Photorhabdus, in Pseudomonas entomophila, in the human pathogens Yersinia enterocolitica and Proteus mirabilis, and in the plant pathogen Pseudomonas syringae. This toxin cannot be classified in any known family of cytotoxins on the basis of amino acid sequences, locus organization, and activity features. It is, therefore, probably the prototype of a new family of binary toxins.
嗜线虫致病杆菌（Xenorhabdus nematophila）是肠杆菌科的一员，它通过强烈抑制免疫系统并在昆虫全身定殖来杀死多种昆虫。一种肽细胞毒素已从嗜线虫致病杆菌的肉汤培养物中纯化出来，并且已经描述了这种毒素对昆虫免疫细胞的溶细胞作用以及对哺乳动物红细胞的溶血作用（里贝罗，C.，维涅斯，M.，和布雷埃林，M.（2003年）《生物化学杂志》278卷，3030 - 3039页）。我们在此表明，这种毒素，嗜线虫致病杆菌α - 嗜线虫溶血素（Xax），可在昆虫和哺乳动物细胞中引发细胞凋亡。我们还报告了嗜线虫致病杆菌中编码这种毒素的两个基因xaxAB的克隆和测序。这两个基因在重组大肠杆菌中的表达导致了活性细胞毒素/溶血素的产生。然而，只有以适当顺序添加这两种肽时才观察到溶血活性。此外，我们在此报告，嗜线虫致病杆菌中xaxAB基因的失活消除了肉汤培养物中存在的主要细胞毒性活性，称为C1。我们还表明，这些基因存在于嗜线虫致病杆菌属和发光杆菌属的各种昆虫病原细菌中，存在于嗜虫假单胞菌（Pseudomonas entomophila）中，存在于人类病原体小肠结肠炎耶尔森菌（Yersinia enterocolitica）和奇异变形杆菌（Proteus mirabilis）中，以及存在于植物病原体丁香假单胞菌（Pseudomonas syringae）中。基于氨基酸序列、基因座组织和活性特征，这种毒素无法归类到任何已知的细胞毒素家族中。因此，它可能是一个新的二元毒素家族的原型。
