Question

.What does the Cry family of proteins specifically do to a target organism? Does this affect any organism that consumes the Cry protein? What is required in the host in order for this protein to be toxic?

Answer 1

• Each Cry protein has some level of target specificity. Cry6Aa has specific toxic action against coleopteran insects and nematodes. The corresponding B. thuringiensis gene, cry6aa, is located on bacterial plasmids. Along with several other Cry protein genes, cry6aa can be genetically recombined in Bt corn and Bt cotton so the plants produce specific toxins.
• Cry toxins interact with specific receptors located on the host cell surface and are activated by host proteases following receptor binding resulting in the formation of a pre-pore structure that directly interacts with membrane lipids and insert into the membrane.
• This bacterium contains the cry proteins in their inactive from. When the inactive toxin protein is ingested by the insect, it gets activated by the alkaline pH of the gut.
• Any organism that consumes this protein is affected as soon as this protein comes in contact with the alkaline pH of the gut. Their primary action is to lyse midgut epithelial cells by inserting into the target membrane and forming pores.

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