Calmodulin (CaM) proteins function to transduce a chemical signal (increase in cytosolic calcium) into a biochemical signal. The ability of the CaM protein to recognize and functionally interact with a target protein is essential in this signal transduction process. In many organisms, with the exception of plants, there exist one or two CaM-type proteins. In the model organism Arabidopsis thaliana there are seven known CaM proteins and five additional CaM-related proteins. Further analysis of the Arabidopsis genome suggests that there are at least an additional 13 potential CaM-related proteins. In this project, the biochemical and functional difference between three CaM-related proteins will be addressed. These proteins all possess conserved cysteine residues, which are proposed to form a disulfide bond. This PI will investigate the role of the cysteine residues and potential disulfide bond formation in calcium binding and in binding to a hydrophobic resin. If disulfide bond formation appears to influence the ability of the proteins to bind calcium and to interact with hydrophobic surfaces, the cysteine residues will be individually mutated. The mutated protein will then be expressed and purified to test the effect of elimination of specific cysteine residues on the biochemical activity of these proteins
