Effect of the distal C terminus of Ca_V1.2 on VDI. (A) Mean normalized currents due to expression of the truncated Ca_V1.2Δ1821 α1 subunit alone or with coexpression of the separate distal C terminus (distal_1822–2171). Data for I_Ca,L from ventricular myocytes is shown for comparison. (B) Mean normalized currents due to the truncated Ca_V1.2Δ1821 α1 subunit coexpressed with a mutant distal C terminus containing the triple mutation EED-QQQ compared with currents due to the channel constructs shown in A. (C) Mean r₁₀₀₀ for truncated Ca_V1.2 expressed alone or with WT or mutant distal C termini (EED-QQQ). Ca_Vβ_2b was used in the experiments in this and all subsequent figures. n = Ca_V1.2Δ1821 alone: 10; Ca_V1.2Δ1821 + distal_1822–2171: 16; Ca_V1.2Δ1821 + EED-QQQ: 10. Mg_i was 0.26 mM.