Figure 6. Effect of calpastatin + ATP on the activity of single α_1C,77 and α_1C,86 channels in the inside-out patch.

Time course of average channel activity (NP_o) of α_1C,77 (A) and α_1C,86 (B) in the cell-attached (c.a.) and inside-out (i.o.) patch before and after addition of calpastatin (2 U ml⁻¹) + Na₂ATP (1 mm). Single-channel activity of α_1C,77 almost completely recovered from run-down in the inside-out (i.o.) patch, whereas almost no effect was observed on channel activity of α_1C,86, which was resistant to run-down in the i.o. patch. C and D depict single-channel traces for the corresponding experiments in A and B, recorded under the indicated conditions. Single channel openings are visible as downward deflections. E, mean channel activity of α_1C,77 and α_1C,86 in the presence of calpastatin + ATP, normalized to the preceding channel activity in the cell-attached configuration. F, representative Western blot analysis (n = 4) of Sigma calpastatin and HEK-tsA201 cell 12000 g supernatant using an anti-calpastatin antibody.