Department of Physiology and Biophysics, Virginia Commonwealth University, 1101 E. Marshall Street, Sanger 3-042a, Richmond, VA 23298, USA.
J Membr Biol. 2011 Feb;239(3):137-56. doi: 10.1007/s00232-010-9333-7. Epub 2010 Dec 9.
Cardiac slow delayed rectifier (I(Ks)) channel complex consists of KCNQ1 channel and KCNE1 auxiliary subunits. The extracellular juxtamembranous region of KCNE1 is an unstructured loop that contacts multiple KCNQ1 positions in a gating-state-dependent manner. Congenital arrhythmia-related mutations have been identified in the extracellular S1-S2 linker of KCNQ1. These mutations manifest abnormal phenotypes only when coexpressed with KCNE1, pointing to the importance of proper KCNQ1/KCNE1 interactions here in I(Ks) channel function. We investigate the interactions between the KCNE1 loop (positions 36-47) and KCNQ1 S1-S2 linker (positions 140-148) by means of disulfide trapping and voltage clamp techniques. During transitions among the resting-state conformations, KCNE1 positions 36-43 make contacts with KCNQ1 positions 144, 145, and 147 in a parallel fashion. During conformational changes in the activated state, KCNE1 position 40 can make contacts with all three KCNQ1 positions, while the neighboring KCNE1 positions (36, 38, 39, and 41) can make contact with KCNQ1 position 147. Furthermore, KCNQ1 positions 143 and 146 are high-impact positions that cannot tolerate cysteine substitution. To maintain the proper I(Ks) channel function, position 143 requires a small side chain with a hydroxyl group, and position 146 requires a negatively charged side chain. These data and the proposed molecular motions provide insights into the mechanisms by which mutations in the extracellular juxtamembranous region of the I(Ks) channel impair its function.
心脏慢延迟整流（I(Ks))通道复合物由 KCNQ1 通道和 KCNE1 辅助亚基组成。KCNE1 的细胞外近膜区是一个无结构的环，以门控状态依赖的方式与多个 KCNQ1 位置接触。已经在 KCNQ1 的细胞外 S1-S2 连接子中鉴定出与先天性心律失常相关的突变。这些突变只有在与 KCNE1 共表达时才表现出异常表型，这表明 KCNQ1/KCNE1 相互作用在这里对 I(Ks) 通道功能非常重要。我们通过二硫键捕获和电压钳技术研究 KCNE1 环（位置 36-47）和 KCNQ1 S1-S2 连接子（位置 140-148）之间的相互作用。在静息状态构象之间的转变过程中，KCNE1 位置 36-43 以平行的方式与 KCNQ1 位置 144、145 和 147 接触。在激活状态的构象变化过程中，KCNE1 位置 40 可以与所有三个 KCNQ1 位置接触，而相邻的 KCNE1 位置（36、38、39 和 41）可以与 KCNQ1 位置 147 接触。此外，KCNQ1 位置 143 和 146 是不能容忍半胱氨酸取代的高影响位置。为了维持适当的 I(Ks) 通道功能，位置 143 需要一个带有羟基的小侧链，而位置 146 需要一个带负电荷的侧链。这些数据和提出的分子运动提供了对 I(Ks) 通道细胞外近膜区突变损害其功能的机制的深入了解。
