Block of RyR2 channels by ShBPs. (A) Representative recordings of individual ryanodine-modified RyR2 channels in symmetrical 210 mM KCl (a) and after the addition of 40 µM ShBP (b), LHBP (c), MHBPI (d), and MHBPII (e) to the solution at the cytosolic (cis) side of the channel. In all cases, the holding potential was 50 mV. Closed, open, and blocked levels are indicated by dashed lines. (B) Rates of peptide association (1/T_o slope [per second/micromolar]; closed circles) and rates of peptide dissociation (mean 1/T_B [per second]; open circles) are plotted against the GRAVY score of the hydrophobic portions of the four peptides: ShBP (1/T_o n = 3–11, 1/T_B n = 3–13), LHBP (1/T_o n = 3–9, 1/T_B n = 4–8), MHBPI (1/T_o n = 3–7, 1/T_B n = 3–6), and MHBPII (1/T_o n = 4–10, 1/T_B n = 4–9). Data are plotted as mean values (±SEM). As MHBPI and MHBPII have the same GRAVY score, MHBPII-related values are signified by “#.”