Figure 1.

C3635A RyR1 does not respond to NO. Specific [³H]ryanodine binding to membrane fractions prepared from HEK293 cells expressing wt-RyR1 (A) or mutant C3635A RyR1 (B) was determined in the presence of 10 μM free Ca²⁺ and increasing concentrations of NO in pO₂ ≈ 10 mmHg (white bars) or pO₂ ≈ 150 mmHg (black bars). [³H]Ryanodine-binding values, determined as described in Experimental Procedures, ranged from 0.05 to 0.15 pmol/mg protein for both wt-RyR1s and C3635A RyR1s. Normalized [³H]ryanodine binding data (100% in the absence of NO for each condition) are the means ± SD of five experiments. *, P < 0.05 when compared with controls in pO₂ ≈ 10 mmHg and pO₂ ≈ 150 mmHg.