Spurious protein activators of Bordetella pertussis adenylate cyclase.

A variety of proteins and tissue preparations (rabbit erythrocyte lysate, catalase, peroxidase, creatine phosphokinase, and lima bean trypsin inhibitor) contain protein activator(s) of the extracellular adenylate cyclase of intact Bordetella pertussis organisms. Stimulation of adenylate cyclase activity of up to 1000-fold over basal activity can be obtained. Activation of the adenylate cyclase is due to the presence of calmodulin in these protein preparations. The criteria to establish this were: Ca2+ dependence of the activation, inhibition by trifluoperazine, heat stability of the activator, chromatographic behavior like authentic calmodulin, and stimulation of cyclic nucleotide phosphodiesterase by the activators. The great sensitivity of the B.pertussis adenylate cyclase assay makes this and ideal system for the detection of trace amounts of calmodulin, in the presence of large amounts of other proteins.