Inhibition of bovine brain cyclic nucleotide phosphodiesterase by a proteinaceous factor from Escherichia coli.

An inhibitory factor for Ca2+ and calmodulin-dependent cyclic nucleotide phosphodiesterase of bovine brain was present in the soluble fraction of Escherichia coli. The factor was heat-stable but trypsin sensitive. The activity of brain phosphodiesterase supported by Ca2+ and calmodulin was inhibited by the factor in a dose dependent manner, but the basal activity was not affected. The inhibition of phosphodiesterase induced by the factor could be abolished by adding large amount of calmodulin, but not by increasing concentration of Ca2+. It was suggested that the factor interacted with calmodulin and thereby inhibited the phosphodiesterase. The factor may be a calmodulin-binding protein in E. coli.