Figure 5

Deletion of the C-terminal tail, but not sequential mutation, results in ablation of CSQ1 regulation of RyR1 gating. (A) to (D). Records of 3 s of single channel activity, where channel opening is upward from zero current (c, continuous line) to maximum open conductance (o, broken line) at +40 mV. (A) Top trace - control activity, with 2 mM cis ATP and 100 nM cis Ca²⁺ free. Middle trace - channel activity increased approximately 2 min after raising trans Cs to 500 mM, indicative of endogenous CSQ1 dissociation [33]. Bottom trace - following perfusion of the trans chamber with control trans solution, and subsequent addition of 16 mg/ml WT CSQ1. (B) to (D) Response of CSQ1-dissociated native RyR1 before (top) and after (bottom) addition of 16 mg/ml trans CSQ1_D∆3 (B), CSQ1_∆C7 (C), and CSQ1_∆C14 (D).