Characterization and purification of a novel calcium binding protein in the nematocysts of Metridium senile

Joshua Oeltjen

Document Type Dissertation/Thesis


Many types of nematocysts, which are stinging structures characteristic of the phylum Cnidaria, have been found to contain high concentrations of calcium (-500mM). I have detected a novel calcium binding protein in the capsular contents of nematocysts of the sea anemone Metridium senile. Collection and purification of the protein was accomplished through the processes of ultrafiltration and ion exchange chromatography. Results from gel staining and calcium overlays were compared to validate the protein's calcium binding properties and to determine the approximate molecular weight of the protein. Calcium binding assays were conducted through the use of 45Ca ultrafiltration and scintillation counting in an effort to determine the dissociation constant (Kd) for the protein and the number of binding sites for calcium. Preliminary calculations suggest that the protein has multiple binding sites and a very low dissociation constant., and it may be a structural protein found within the capsular or tubular components of the nematocyst.