Potency of drug action is usually determined by binding to a specific receptor site on target proteins. In contrast to this conventional paradigm, we show here that potency of local anesthetics (LAs) and antiarrhythmic drugs (AADs) that block sodium channels is controlled by fenestrations that allow drug access to the receptor site directly from the membrane phase. Voltage-gated sodium channels initiate action potentials in nerve and cardiac muscle, where their hyperactivity causes pain and cardiac arrhythmia, respectively. LAs and AADs selectively block sodium channels in rapidly firing nerve and muscle cells to relieve these conditions. The structure of the ancestral bacterial sodium channel NaVAb, which is also blocked by LAs and AADs, revealed fenestrations connecting the lipid phase of the membrane to the central cavity of the pore. We cocrystallized lidocaine and flecainide with NavAb, which revealed strong drug-dependent electron density in the central cavity of the pore. Mutation of the contact residue T206 greatly reduced drug potency, confirming this site as the receptor for LAs and AADs. Strikingly, mutations of the fenestration cap residue F203 changed fenestration size and had graded effects on resting-state block by flecainide, lidocaine, and benzocaine, the potencies of which were altered from 51- to 2.6-fold in order of their molecular size. These results show that conserved fenestrations in the pores of sodium channels are crucial pharmacologically and determine the level of resting-state block by widely used drugs. Fine-tuning drug access through fenestrations provides an unexpected avenue for structure-based design of ion-channel-blocking drugs.

中文翻译：

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窗孔控制电压门控钠通道的静止状态阻滞。

通常通过结合靶蛋白上的特定受体位点来确定药物作用的效力。与这种传统范例相反，我们在这里表明，阻断开钠通道的局麻药（LAs）和抗心律不齐药物（AADs）的药效是由开窗控制的，开窗允许药物直接从膜相进入受体部位。电压门控性钠通道在神经和心肌中引发动作电位，它们的过度活跃会分别引起疼痛和心律不齐。LA和AAD选择性地阻断快速刺激的神经和肌肉细胞中的钠通道，以缓解这些状况。祖先细菌钠通道NaVAb的结构也被LA和AAD阻断，显示出开窗将膜的脂质相连接到孔的中心腔。我们将利多卡因和氟卡尼与NavAb共结晶，显示出在孔中心腔中强大的药物依赖性电子密度。接触残基T206的突变大大降低了药效，证实了该位点是LA和AAD的受体。令人惊讶的是，开窗帽残基F203的突变改变了开窗尺寸，并通过氟卡尼，利多卡因和苯佐卡因对静息状态的阻滞产生了分级影响，它们的效价从其分子大小从51倍改变为2.6倍。这些结果表明，钠通道孔中保守的开窗在药理学上是至关重要的，并决定了广泛使用的药物的静息状态阻断水平。通过开窗对药物进行微调，为基于结构的离子通道阻断药物的设计提供了意想不到的途径。