Professor of Biochemistry
Protein engineering of insecticidal toxins is the major research interest in my laboratory. The ultimate goal of these studies is to understand the structure/function relationships of these proteins to create more specific and environmentally safer pesticides.
One project involves locating the functional domains of insecticidal crystal proteins (ICPs) of Bacillus thuringiensis. Site-directed mutagenesis and homology switches of portions of genes which display different insecticidal activity have created a set of mutants which allows us to identify the "specificity domains" on two ICPs. Intensive site-directed mutagenesis will reveal which amino acids are involved in the insecticidal activity.
Another project involves the mechanism of action of the ICPs. The interaction of the toxins with membrane receptors is being analyzed by kinetic analysis of binding and location of the binding sites using brush border membrance vesicles and insect tissue culture cell. Purificaton and analysis of receptors are one aspect of this project; mutations of the toxin protein to analyze the protein-protein interaction of toxin-receptor binding is another. Electrophysiological techniques (patch and voltage clamps) are used to measure the effects of mutations on the ion channel function of ICP.
We also examine expression of insecticidal proteins in foreign organisms in my laboratory. Overexpression in E. coli allows mutant proteins to be produced to greater than 50 percent of total cellular protein allowing rapid purification of protein for biochemical study and insect bioassay. In addition, we are interested in the expression of ICPs in plants, in collaboration with other scientists at Ohio State and elsewhere. Other aspects of Bacillus genetics and the genetics of Bacillus bacteriophages are also under investigation.