Antigens are often presented in a more natural context, for example as surface arrays and with molecules with adjuvant activity, and this tends also to enhance the immune response. V. Discuss the genetics, structure and mode of action of insecticidal Cry proteins. The 65Kd proteins are naturally truncated versions of the 135 Kd toxins. There are now at least twenty distinct cry gene families and over ninety distinct cry genes identified. A single protein monomer can form bipyramidal crystals in a heterologous host and is an active toxin.
Toxins can form bipyramidial, cuboid, flat or round crystals.
Inclusions can contain multiple Cry proteins and assembly may require additional factors. Cry proteins bind specifically to intestinal epithelial brush border membranes in susceptible insects. There are specific high-affinity receptors in the insect midgut. Describe the mechanisms by which morphogenesis is coupled to gene expression during sporulation. Two separate programs of gene expression occur within the mother cell and forespore compartments, with a complex set of cross-checking mechanisms to ensure that events in one compartment do not occur until obligatorily previous events in the other are successfully completed.