, 2001). Mcf toxins cause damage to the insect midgut after injection into larvae with loss of body turgor and a ‘floppy’ phenotype of the caterpillars (Dowling et al., 2004). Injection of PVCs destroys insect hemocytes, which undergo dramatic actin cytoskeleton condensation (Yang et al., 2006). Pir toxins act as binary proteins. Both PirA and PirB proteins are necessary for insecticidal activity. Injection of either PirA or PirB alone into caterpillars of Galleria is not associated with any mortality, and mixture of individual PirA and PirB preparations exhibits full activity against this insect (Waterfield et al., 2005). Histological examination of Plutella xylostella larvae fed

with recombinant Escherichia coli expressing PirA and PirB proteins reveals gross abnormalities of the midgut epithelium, with profound swelling and shedding of the apical membranes (Blackburn et al., 2006). PirAB toxins SB203580 clinical trial also show larvicidal activity

against mosquito larvae (Aedes aegypti and Aedes albopictus; Ahantarig et al., 2009). Binary toxins have also been reported in several other bacteria, including Clostridium botulinum C2 toxin, Clostridium difficile toxin (CDT), Clostridium perfringens iota (ι) toxin, Clostridium spiroforme toxin (CST), Bacillus anthracis edema and lethal toxins, as well as the Bacillus cereus vegetative insecticidal proteins (VIP; Barth et al., 2004). Normally, binary toxins consist of binding component and enzymatic component. The binding component recognizes a cell surface receptor and allows the internalization of the enzymatic component into the cytosol, and the enzymatic component catalyzes the reaction and induces Cabozantinib cell line the toxicity (Carman et al., 2011). Recently, a new binary toxin gene xaxAB from Xenorhabdus nematophila, a bacterial species closely related to P. luminescens, was cloned and sequenced. XaxAB toxin exhibited both

necrotic and apoptotic activities in both insect and mammalian cells in vitro. Incubations of sheep red blood cells with XaxAB showed that maximum hemolytic activity was obtained with equimolar concentrations of XaxA and XaxB. This binary toxin cannot be classified in any known family of cytotoxins on the basis of amino acid Reverse transcriptase sequences, locus organization, and activity features. The putative hemolysin loci, containing two closely linked genes similar to xaxAB, were also found to be present in the chromosome of Photorhabdus, Pseudomonas, and Yersinia (Vigneux et al., 2007). Analysis of the genomic sequence of P. luminescens TT01 (Duchaud et al., 2003) revealed that amino acid sequences encoded by plu1961 and plu1962 showed 76.8% and 74.9% similarity to XaxA and XaxB, respectively. To evaluate the biological activity of this potential binary toxin, plu1961 and plu1962 were cloned and expressed in E. coli. Both oral and injectable toxicities of Plu1961/Plu1962 were assayed against insect larvae. Cytotoxic effect of binary toxin was tested against insect midgut CF-203 cells and mammalian cell lines.