Figure 5.

Effects of Ca_vβ subunits on properties of Ca_v2.1 Ca²⁺ channels. Ca_v2.1 and α₂δ subunits were expressed without (▵) or with Ca²⁺-channel β_1b (●) or β₃ (○) subunits in tsA-201 cells. (A) Voltage dependence of activation and inactivation measured as in Fig. 1. (B) Time constants of inactivation determined during 1,000-ms long test pulses to the indicated potentials. (C) Ca_v2.1 and α₂δ subunits were expressed with Ca²⁺-channel β₃ subunits and studied in the presence (○) or absence (●) of intracellular GTPγS. (D) Ca_v2.1 and α₂δ subunits were expressed and studied in the presence (▵) or absence (▴) of GTPγS. (E and F) Activation curves recorded with intracellular GTPγS in the absence (○) and presence (●) of a preceding conditioning prepulse as described for Fig. 1 from cells coexpressing α₁2.1, α₂δ, and Caβ_1b (E) or α₁2.1 and α₂δ alone (F).