Role of Calmodulin in Brain Function

Abstract

This chapter reviews the salient features of calmodulin and some of the recent findings on its role in cellular processes of the brain. Calmodulin is a single polypeptide with 148 amino acids and a molecular weight of 16 700. Some 30 % of its amino acids consist of aspartate or glutamate, which accounts for the low isoelectric point (4.3). It contains no cysteine, hydroxyproline or tryptophan, but does contain a trimethylated lysine at position 115. One striking characteristic of calmodulin is its tendency to retain biologic activity after exposure to heat (99oC), urea (8 M), acidic pH and detergents. Another is its lack of both tissue and species specificity. A third is that calmodulin from a variety of sources possesses many similar physicochemical properties. Calmodulin isolated from certain sources contains no trimethylated lysine and appears to be equally active, at least in activating bovine brain phosphodiesterase. The lack of cysteine and hydroxyproline would allow calmodulin to have a flexible tertiary structure, a desirable feature for a multifunctional protein that interacts with many different receptor proteins.