Chimeric CA2+/Calmodulin-Dependent Protein Kinase in Plants

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Abstract 9630337 Poovaiah Protein phosphorylation is one of the major mechanisms for transducing extracellular signals to intracellular responses. Calcium is important in mediating a number of signaling pathways, and Ca+/Calmodulin (CM) regulated protein phosphorylation amplifies and modifies Ca mediated signals. Several Ca/CaM dependent protein kinases have been well characterized in mammalian systems, but little is known about Ca/CaM dependent protein kinases in plants. The laboratory of the PI has cloned a chimeric Ca/CaM dependent protein kinase gene from developing anthers. This CCaMk contains a catalytic domain, a CaM binding domain and a visin-like Ca binding domain in one polypeptide. This protein is distinct form other known plant and animal kinases, and its structure suggests it may have evolved from the fusion of two genes that are functionally and phylogenetically diverse. This is the first evidence for a Ca/CaM dependent protein kinase in plants. In this grant the structure function relationships of CCaMK as well as the effects of altered levels in the plant, will be examined. Deletion and point mutants will be studied to determine the function of the regulatory domain, and the role of autophosphorylation sites will be confirmed using site directed mutants. Synthetic peptides will be used to identify and study the autoinhibitory domain. The effect of altered expression of CCaMK will be observed in transgenic plants with sense or antisense constructs of the CCaMK gene. These studies should establish the presence and the role of this important enzyme in plants. *** ***