Cry1 holotype toxins of Bacillus thuringiensis

Bacillus thuringiensis is a gram-positive bacterium which produces insecticidal parasporal crystal proteins (ICPs) during stationary phase of its growth cycle. Cry1 halotype toxins form the largest class of insecticidal crystal proteins which are produced as protoxins (130 kDa). These proteins are toxic to lepidopteron insects and coleopteran insects. Many of these ICPs have been used to produce genetically modified plants and biopesticidal formulations. Cry1 mutant toxins with more insecticidal properties have been developed by protein engineering techniques such as single or multiple amino acid changes in variable and conserved regions. These have also helped to define better the functions of helices of these crystal proteins in membrane binding, membrane insertion and toxicity. Synthetic Cry1 proteins have been synthesized for better expression in plants. Number of patents related to Cry1 toxins have been filed and published across the globe. Many reviews have been written regarding Cry proteins but in our knowledge no review has been written focusing separately on one class of these toxins. In this review we described the cry1 genes and their crystal protein toxins.