It is well established that Ca2+ is a pleiotrophic factor affecting a wide variety of essential cellular processes. It is postulated that many of these actions are mediated via calmodulin. In fact, it is felt that the Ca2+ calmodulin complex may represent the active cellular state of Ca2+. Since all cells contain calmodulin and Ca2+, the specificity of Ca2+ calmoduling action in cells is somewhat of an enigma. Our results, as well as published results of others suggests that specificity of Ca2+ action resides in the calmodulin acceptor proteins (CAPs). That is, the response of any particular cell type to elevated Ca2+ levels is dependent upon the class and population of CAPs. These proteins represent a variety of enzymes which are regulated by Ca2+ calmodulin. It is very possible that the CAPs themselves possess enzyme modifying properties (i.e. protein kinase and methylases). The tissue specificity of such a situation would be extended to not only the CAPs, but the presence of CAP protein substrate as well. We propose to continue our purification of CAPs from electroplax and chicken gizzard. These studies include the subunit structure, immunolocalization, and expression during different physiological states in hopes of better understanding their individual functional roles. We have recently discovered several other high-affinity calcium receptor proteins which form calcium induced hydrophobicity. Due to their functional similarity with troponin C and calmodulin we have referred to them as """"""""calcimedins"""""""". We now have the ability to purify these proteins in high quantity in order to pursue a complete physicochemical characterization, produce antibodies, develop immunoassays, and study their functional role in cell regulation. Collectively, our studies will provide a better understanding regarding the mediation and selective discrimination of the regulatory intracellular calcium signal.
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