FIGURE 8.

Hypothetical model for ion pore of RyR1. The RyR1 pore model, which was obtained by modifying by “hand” the published structure of K⁺ channels (24,26), shows the putative position of lumenal amino acid residues D⁴⁸⁹⁹ and E⁴⁹⁰⁰ and cytosolic amino acid residues G⁴⁹³⁴, D⁴⁹³⁸, D⁴⁹⁴⁵, and E⁴⁹⁵⁵. The inner transmembrane helix in RyR1 is analogous to S6 in 6TM K⁺ channels (such as Shaker and KvAP) and M2 in 2TM K⁺ channels (such as KcsA and Kir). Note only two of the four pore-forming segments are shown.