Interactions of basic polypeptides and proteins with calmodulin

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Abstract
Low concentrations (< 10 .mu.g/ml) of a number of highly basic polypeptides inhibit the calmodulin-stimulated cyclic nucleotide phosphodiesterase. Inhibitory compounds include synthetic polypeptides [polylysine (D and L) and polyarginine] and basic proteins (protamine, histones H1, H2A, H2B, H3 and H4 and myelin basic protein). Polylysine of MW about 2000 or higher was inhibitory, but pentalysine did not inhibit. Other basic proteins and compounds did not inhibit, including bradykinin, spermine and putrescine. In mixtures of calmodulin and basic protein, complexes were formed whether Ca2+ was present or not. This was true for polylysine, myelin basic protein and histone H2B. The inhibition of the phosphodiesterase is apparently due to interaction of these basic proteins with calmodulin. The wide variety of basic polypeptides and proteins that affect the calmodulin stimulation of phosphodiesterase indicates that these interactions are not specific.

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