The protein calmodulin is the principle transducer of messenger calcium. It is believed to exist within the cytosols of all cells of all eukaryotes. In its calcium forms, (but not in other forms) it activates at least ten and probably as many as twenty different enzymes or structural proteins. It has evolved by gene duplication and is very highly conserved especially among the animals. Previous crystal structure studies have revealed that calmodulin consists of two protein lobes joined by a short pepitde linking chain. This proposal is to study two crystal structures of proteins related to calmodulin. Crystals suitable for x-ray diffraction studies have already been grown. The significance of these determinations is their test of the model in which the central linker of calmodulin functions as a flexible tether allowing specific patches on the two labels to enfold a target.
