Figure 4. Domain II SF Mutations Reduce CDI in Ca_V1.3 and Ca_V2.1.

(A) Exemplar normalized recordings at +20 mV in Ca²⁺ (black) or Ba²⁺ (gray) from HEK293 cells expressing Ca_V1.3 or the indicated mutants.

(B) Fractional current remaining 300 ms post-depolarization (R₃₀₀) as a function of the membrane potential for (A).

(C) Average f values at +20 mV. *p < 0.01 and **p < 0.001 compared to Ca_V1.3.

(D) I–V relationships for Ca_V1.3 (black circles), Ca_V1.3 D707A (blue triangles), and Ca_V1.3 E1121A (red orange squares).

(E) Voltage-dependent activation curves for the indicated channels. Symbols are as in (D).

(F) Exemplar normalized recordings at +10 mV in Ca²⁺ (black) or Ba²⁺ (gray) from HEK293 cells expressing Ca_V2.1 or the indicated mutants.

(G) Fractional current remaining 800 ms post-depolarization (R₈₀₀) as a function of the membrane potential for (F).

(H) Average f′ values at +10 mV, where is f′ the difference between Ca²⁺ and Ba²⁺ R₈₀₀ values. *p < 0.01 and **p < 0.001 compared to Ca_V2.1.

(I) I–V relationships for Ca_V2.1 (open circles), Ca_V2.1 D667A (green triangles), and Ca_V2.1 E1461A (purple squares).

(J) Voltage-dependent activation curves for the indicated channels. Symbols are as in (I).