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 activity, which was more than ten times higher than that of wild-type calcineurin, the calcineurin-immunosuppressant/immunophilin interaction, the effect of metal ions and calcineurin subunit interaction. We propose that the change of the activity and function of V314 is due to conformational changes of calcineurin to benefit the binding of, or stimulation by, Mn2+, or to affect the interaction between the A and B subunits.