Figure 2

Modulation of ryanodine receptors (RyRs) by Ca²⁺. (A) Ensemble currents of single RyR2 show the effect of fast Ca²⁺ pulses on the P_o of a non-phosphorylated channel ('control') or the same channel after phosphorylation with the catalytic subunit of protein kinase A ('+PKA'). Laser photolysis of 'caged Ca²⁺' (o-nitrophenyl EGTA, tetrapotassium salt; NP-EGTA) increased [Ca²⁺] from 0.1 to 10 μmol/l at the point labeled as 'Ca²⁺ pulse' (modified from [51]. (B) Ca²⁺-P_o curves of RyR1 and RyR2. Channel activity was measured at the indicated stationary concentrations of Ca²⁺ ('RyR1' and 'RyR2 steady-state') and right after a fast Ca²⁺ pulse, as in (A) ('RyR2 (peak P_o)') (unpublished results) (see text for details).