Abstract
Cyt1A protein is a cytolytic protein encoded by the cyt gene of Bacillus thuringiensis subsp. israelensis (Bti) as part of the parasporal crystal proteins produced during the sporulation. Cyt1A protein is unique compared to the other endotoxins present in these parasporal crystals. Unlike δ-endotoxins, Cyt1A protein does not require receptors to bind to the target cell and activate the toxicity. It has the ability to affect a broad range of cell types and organisms, due to this characteristic. Cyt1A has been recognized to not only target the insect cells directly, but also recruit other endotoxins by acting as receptors. Due to these mode of actions, Cyt1A has been studied for its cytolytic activity against human cancer cell lines, although not extensively. In this study, we report a novel Cyt1A protein produced by a Bti strain QBT229 isolated from Qatar. When tested for its cytotoxicity against lung cancer cells, this local strain showed considerably higher activity compared to that of the reference Bti and other strains tested. The possible reasons for such enhanced activity were explored at the gene and protein levels. It was evidenced that five consecutive amino acid replacements in the β8 sheet of the Cyt1A protein enhanced the cytotoxicity against the lung epithelial cancer cells. Such novel Cyt1A protein with high cytotoxicity against lung cancer cells has been characterized and reported through this study.
Highlights
Bacillus thuringiensis (Bt) is a Gram-positive, spore forming, aerobic soil bacterium found in different environments [1]
The standard MTT assay for quantifying the cytotoxic activity of the Bt proteins was performed for this study with some modifications
It was observed that the cytotoxic activity among these Qatari Bt strains were higher compared to the reference strain H14
Summary
Bacillus thuringiensis (Bt) is a Gram-positive, spore forming, aerobic soil bacterium found in different environments [1]. It belongs to the six-member group of Bacillus cereus, including others like Bacillus anthracis, Bacillus cereus, Bacillus weihenstephanensis, Bacillus pseudomycoides, and Bacillus mycoides. The parasporal crystals are made up of many insecticidal proteins called δ-endotoxins including Cry toxins and cytolytic proteins called Cyt toxins [3]. It has Toxins 2018, 10, 125; doi:10.3390/toxins10030125 www.mdpi.com/journal/toxins.
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