Properties of Na_V1.4₁₇₄₀-glycine-CaM. (A) Representative raw current records of truncated Na_V1.4 channels with CaM linked to the CT by 4 (top, Na_V1.4₁₇₄₀–G4–CaM) or 14 (bottom, Na_V1.4₁₇₄₀–G14–CaM) glycine residues. The IV relationships reveal no significant differences between the channels linked to CaM and wild-type Na_V1.4 (right). (B) Recovery from inactivation of Na_V1.4₁₇₄₀–G4–CaM (○) and Na_V1.4₁₇₄₀–G14–CaM (▵) are slower than that of wild-type, full-length Na_V1.4 (□). (C) The rates of entry into inactivated states are similar in Na_V1.4₁₇₄₀–G4–CaM (○), Na_V1.4₁₇₄₀–G14–CaM (▵), and wild-type Na_V1.4 (□) channels. (D) Overexpression of wild-type CaM (•) but not CaM₁₂₃₄ (⊗) shifts the steady-state inactivation curve in the hyperpolarizing direction compared with Na_V1.4₁₇₄₀–G4–CaM (○) or wild-type Na_V1.4 (□) expressed alone. (E) The steady-state inactivation curve of Na_V1.4₁₇₄₀–G14–CaM (▵) is unaffected by overexpression of CaM (▴) or CaM₁₂₃₄ ().