Anti-cancer Parasporin Toxins are Associated with Different Environments: Discovery of Two Novel Parasporin 5-like Genes

Abstract

Cry toxins are primarily a family of insecticidal toxins produced by the bacterium Bacillus thuringiensis (Bt). However, some Cry toxins, called parasporins (PSs), are non-insecticidal and have been shown to differentially kill human cancer cells. Based on amino acid homology, there are currently six different classes of parasporins (PS1-6). It is not known what role parasporins play in nature, nor if certain PSs are associated with Bt found in particular environments. Herein, we present ten parasporin-containing isolates of Bt from the Caribbean island of Trinidad. Genes coding for PS1 and PS6 were found in isolates associated mainly with artificial aquatic environments (e.g., barrels with rain water), while Bt possessing two novel PS5-like genes (ps5-1 and ps5-2), were isolated from manure collected directly from the rectum of cattle. The amino acid sequences inferred from the two PS5-like genes were 51 % homologous to each other, while being only 41 or 45 % similar to PS5Aa1/Cry64Aa, the only reported member of the parasporin five class. The low level of amino acid homology between the two PS5-like genes and PS5Aa1 indicate that the two PS5-like genes may represent a new class of parasporins, or greatly expand the level of diversity within the current parasporin 5 class.

Bacillus spp.: Attractive Sources of Anti-cancer and Anti-proliferative Biomolecules

“…proteins are yet to be classi ed (Poornima et al, 2010;Gonzalez et al, 2011;Ammons et al, 2016). Among these six classes of parasporin, only PS1 kills cancer cells by activating apoptotic signaling pathway causing from attenuation of cellular protein and DNA synthesis, and by increasing in ux of calcium ions (Katayama et al,2007).…”

Cry64Ba and Cry64Ca, Two ETX/MTX2-Type Bacillus thuringiensis Insecticidal Proteins Active against Hemipteran Pests

“…The sequences of the two cry genes were identical with the previously reported cry64Ba and cry64Ca genes, respectively (GenBank accession no. KC960014) (11). In addition, we conclude that the cry64Ba and cry64Ca genes are plasmid encoded since these genes were located at scaff_269 in the genome draft sequence and a BLASTN search revealed that scaff_269 shows 99% identity with plasmid pYGD98 from the Bacillus thuringiensis strain YGd22-03.…”

“…Here, we report novel features of two Bt Cry toxins, Cry64Ba and Cry64Ca, which were previously identified from Bt isolates showing toxicity against HepG2 cancer cells (11). We cloned both genes and confirmed that Cry64Ba and Cry64Ca proteins expressed together in an acrystalliferous Bt strain showed high insecticidal activity against rice planthoppers but no cytotoxicity against HepG2 cells.…”

Isolation, Cloning, DNA Sequencing and Bioinformatics Analysis of the Parasporin–1 Gene of Bacillus thuringiensis

“…In preliminary screening test using sheep erythrocytes, it was observed that parasporal proteins obtained from the 60 strains were capable of inducing a strong hemolytic response. It is now known that such hemolysis is affected by broad-spectrum cytolysins (Cyt proteins) that are active on a wide range of invertebrate and vertebrate cells [17]. A total of 1,684 strains that lacked obvious hemolytic parasporal proteins were then examined for in vitro cytocidal activity against MOLT-4 cells (human leukemic T-cells).…”