High activity of the calcineurin A subunit with a V314 deletion

A deletion mutant (V314) of the calcineurin A subunit was constructed using site-directed mutagenesis. Its phosphatase activity and function were then characterized. The V314 deletion significantly altered the phosphatase act ivity, which was more than ten times higher than that of wild-type calcineu rin, the calcineurin-immunosuppressant/immunophilin interaction, the effect of metal ions and calcineurin subunit interaction. We propose that the cha nge of the activity and function of V314 is due to conformational changes o f calcineurin to benefit the binding of, or stimulation by, Mn2+, or to aff ect the interaction between the A and B subunits.