What they found
Characterization of calcineurin’s dual Ca²⁺-sensing mechanism: calmodulin binding to the CaM-binding domain increases catalytic rate and modulates Ca²⁺ response; calcineurin B (regulatory subunit) sets baseline Ca²⁺ sensitivity. Together they produce highly cooperative Ca²⁺ activation (Hill n = 2.8–3). Half-maximum Ca²⁺ concentration for activation: 0.6–1.3 µM depending on CaM concentration.
Numbers that matter
- Ca²⁺ for half-max calcineurin activation: 0.6–1.3 µM (model Kd_CaN = 500 nM is slightly below range — a minor underestimate)
- Hill coefficient: 2.8–3 (model n_CaN_Hill = 4.0 is slightly steeper than measured)
- CaM increases catalytic turnover rate ~10-fold at saturating Ca²⁺
- Calcineurin B shifts Ca²⁺ sensitivity to lower concentrations
Fit to h05
The RBM24 ODE model uses Kd_CaN = 500 nM and n_CaN_Hill = 4.0. Stemmer & Klee 1994 gives 600–1300 nM and Hill n = 2.8–3. Both values deviate modestly: Kd is ~20% low (conservative — makes CaN activate earlier), Hill n is ~35% steep (makes CaN more switch-like). Neither is a fatal error for the qualitative CaMKII:CaN decoding hypothesis.
Connections
- STRC Calcium Oscillation Acoustic Therapy — CaN kinetics in RBM24 ODE
[see-also]1998-dolmetsch-calcium-oscillations-gene-expression — downstream of CaN[part-of]calcium-oscillation (literature-params topic)