In the next grant year, we will continue to pursue our original objectives: (1) to characterize phosphodiesterase from bovine brain with emphasis on its regulatory properties, multiple forms and submit structure, and (2) to determine what cellular functions that calmodulin regulates in the brain other than cAMP metabolism. The latter includes studies on the subcellular localization of calmodulin using immunocytochemical techniques and the identification of calmodulin-binding proteins using conventional biochemical techniques as well as bifunctional crosslinking reagents.