Hydrophobic properties of Tetrahymena calmodulin related to the phosphodiesterase activity

Abstract

We have examined hydrophobic properties of Tetrahymena CaM using the uncharged probe, n-phenyl-1-naphthylamine (NPN) fluorescence. The maximal flurorescence intensity of Tetrahymena calmodulin (CaM) is < 1/12 of the bovine brain CaM. In the phosphodiesterase activation, the potency of Tetrahymena CaM, which was represented by reciprocals of the quantity of CaM required for half-maximal activation of enzyme was 22.7% respectively, of that of the bovine brain CaM. Here, Tetrahymena CaM had less hydrophobic groups exposed in the presence of Ca 2+. Then Ca 2+-CaM dependent enzymes require much amount of Tetrahymena CaM, comparing with the bovine brain CaM.