Vanadium (IV) inhibits calmodulin-stimulated skeletal muscle myosin light chain kinase activity.

Vanadium, believed to be an essential trace metal, exhibits numerous biological effects. Using electron spin resonance spectroscopy, we have demonstrated that vanadyl, vanadium (IV), the predominant intracellular form of vanadate (vanadium V), binds to calmodulin in the presence of physiological concentrations of magnesium, extending earlier work which showed competitive binding of vanadyl and calcium to calmodulin. In the presence of a magnesium-containing buffer, vanadyl does not lead to calmodulin activation of the calmodulin-dependent enzyme, rabbit skeletal muscle myosin light chain kinase; in the presence of calcium, vanadyl is a potent inhibitor of the calmodulin-activated form of the kinase. Thus, vanadyl can potentially interfere with some of the intracellular actions of calcium, presumably via binding to calmodulin. This observation deserves consideration in view of the potential clinical application of vanadium treatment to mimick insulin action and lower blood glucose.