The voltage-gated calcium channel Ca_V1.1 belongs to the family of pseudo-heterotetrameric cation channels, which are built of four structurally and functionally distinct voltage-sensing domains (VSDs) arranged around a common channel pore. Upon depolarization, positive gating charges in the S4 helices of each VSD are moved across the membrane electric field, thus generating the conformational change that prompts channel opening. This sliding helix mechanism is aided by the transient formation of ion-pair interactions with countercharges located in the S2 and S3 helices within the VSDs. Recently, we identified a domain-specific ion-pair partner of R1 and R2 in VSD IV of Ca_V1.1 that stabilizes the activated state of this VSD and regulates the voltage dependence of current activation in a splicing-dependent manner. Structure modeling of the entire Ca_V1.1 in a membrane environment now revealed the participation in this process of an additional putative ion-pair partner (E216) located outside VSD IV, in the pore domain of the first repeat (IS5). This interdomain interaction is specific for Ca_V1.1 and Ca_V1.2 L-type calcium channels. Moreover, in Ca_V1.1 it is sensitive to insertion of the 19 amino acid peptide encoded by exon 29. Whole-cell patch-clamp recordings in dysgenic myotubes reconstituted with wild-type or E216 mutants of GFP-Ca_V1.1e (lacking exon 29) showed that charge neutralization (E216Q) or removal of the side chain (E216A) significantly shifted the voltage dependence of activation (V_1/2) to more positive potentials, suggesting that E216 stabilizes the activated state. Insertion of exon 29 in the GFP-Ca_V1.1a splice variant strongly reduced the ionic interactions with R1 and R2 and caused a substantial right shift of V_1/2, whereas no further shift of V_1/2 was observed on substitution of E216 with A or Q. Together with our previous findings, these results demonstrate that inter- and intradomain ion-pair interactions cooperate in the molecular mechanism regulating VSD function and channel gating in Ca_V1.1.

电压门控钙通道 Ca _V 1.1 属于假异四聚体阳离子通道家族，该通道由四个结构和功能不同的电压传感域 (VSD) 组成，这些电压传感域排列在公共通道孔周围。去极化后，每个 VSD 的 S4 螺旋中的正门控电荷穿过膜电场，从而产生促使通道打开的构象变化。这种滑动螺旋机制得益于离子对与 VSD 内 S2 和 S3 螺旋中反电荷相互作用的瞬时形成。_{最近，我们在 Ca V} 1.1的 VSD IV 中发现了 R1 和 R2 的域特异性离子对伴侣，它稳定了该 VSD 的激活状态，并以剪接依赖性方式调节电流激活的电压依赖性。膜环境中整个 Ca _V 1.1 的结构建模现在揭示了位于 VSD IV 外部、第一个重复序列 (IS5) 的孔域中的另一个假定离子对伴侣 (E216) 参与这一过程的过程。_{这种域间相互作用是 Ca V} 1.1 和 Ca _V 1.2 L 型钙通道特有的。此外，在 Ca _V 1.1 中，它对外显子 29 编码的 19 个氨基酸肽的插入敏感。用 GFP-Ca _V 1.1e 的野生型或 E216 突变体（缺乏外显子）重建的基因缺陷肌管中的全细胞膜片钳记录29）表明电荷中和（E216Q）或侧链去除（E216A）显着地将激活的电压依赖性（V _1/2）转移到更正的电位，表明E216稳定了激活状态。在 GFP-Ca _{V 1.1a 剪接变体中插入外显子 29 强烈减少了与 R1 和 R2 的离子相互作用，并引起 V 1/2}的显着右移，而在 E216 取代时没有观察到V _1/2的进一步移动结合我们之前的发现，这些结果表明域间和域内离子对相互作用在调节 Ca _V 1.1 中 VSD 功能和通道门控的分子机制中相互配合。