Spurious Protein Activators of Bordetella pertussis Adenylate Cyclase

Abstract

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 B. 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 an ideal system for the detection of trace amounts of calmodulin in the presence of large amounts of other proteins. (Whole or disrupted B. pertussis reportedly alter adrenergic function when injected into animals, implying that the bacterium might stimulate a mammalian adenylate cyclase.).