[Interaction of tertiapin, a neurotoxin from bee venom, with calmodulin]

Tertiapin, a neurotoxin from the honey bee venom, interacts specifically with calmodulin in the presence of Ca2+. The nature of this interaction was studied using calmodulin-cAMP phosphodiesterase system. Tertiapin does not affect the unstimulated basal activity of phosphodiesterase. However, it totally inhibits the enzyme-activating capacity of calmodulin. Analysis of the dose-dependent activation of phosphodiesterase by calmodulin in the presence of tertiapin indicated that inhibition is caused by the interaction of two tertiapin molecules with calmodulin (Kd 2 microM). The data obtained suggest that the toxic effect of tertiapin in nervous tissue is mediated by blockade of calmodulin function.