BT CRYSTAL TOXIN: MECHANISMS OF RESISTANCE AND ACTION

Stanford University, Stanford CA

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Crystal (Cry) proteins made by the soil bacterium Bacillus thuringiensis (Bt) are harmless to vertebrates, but they highly toxic to insects and nematodes. Their value in controlling insects that destroy crops and transmit human diseases is well established. It was found that Cry5B, a purified crystal protein from Bt, is highly toxic to a wide range of free- living nematodes, including a human and animal hookworm parasite A. ceylanicum. Previous data suggest that Cry5B may be used in the future to control nematodes of human and animals. However, widespread use of Cry proteins in crops and organic farming develops resistance among target populations. The targeted insects or nematodes may develop resistance to crystal proteins by modifying their receptors. In order to understand the interaction between the crystal proteins and their receptors, we purified and crystallized the elastase-activated fragment of Cry5B. For determining the Cry5B structure, it is critical to obtain high resolution diffraction data at synchrotron. If we can solve Cry5B structure (never solved before), if possibly, complex with its receptor, it will help understand how the protein interact with its receptor. In addition, it will provide important information to engineer the protein binding region and make the affinity stronger to overcome the resistance from the targets.