Effect of Vanadyl Ions on calcineurin and Its A Subunit

摘要

Calcineurin (cn) exhibits a bimodal regulation by different concentrations of vanadyl ions (VO~(2+)) in the presence of Mn~(2+), Low concentrations of VO~(2+) inhibit the enzyme, with 50μm VO~(2+) completely inhibiting CN activity, while high concentrations, up to 500μm VO~(2+), stimulate the CN activity. A similar bimodal regultion of CN was not observed with either calcium or vanadate under the same conditions. X-band electron spin resonance spectroscopy, used to study the binding of VO~(2+) to the catalytic subunit A of calcineurin, show that there are two kinds of binding sites in the A subunit.