Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan.
Proc Natl Acad Sci U S A. 2010 Nov 2;107(44):18862-7. doi: 10.1073/pnas.1010354107. Epub 2010 Oct 20.
The KCNQ1 voltage-gated potassium channel and its auxiliary subunit KCNE1 play a crucial role in the regulation of the heartbeat. The stoichiometry of KCNQ1 and KCNE1 complex has been debated, with some results suggesting that the four KCNQ1 subunits that form the channel associate with two KCNE1 subunits (a 42 stoichiometry), while others have suggested that the stoichiometry may not be fixed. We applied a single molecule fluorescence bleaching method to count subunits in many individual complexes and found that the stoichiometry of the KCNQ1 - KCNE1 complex is flexible, with up to four KCNE1 subunits associating with the four KCNQ1 subunits of the channel (a 44 stoichiometry). The proportion of the various stoichiometries was found to depend on the relative expression densities of KCNQ1 and KCNE1. Strikingly, both the voltage-dependence and kinetics of gating were found to depend on the relative densities of KCNQ1 and KCNE1, suggesting the heart rhythm may be regulated by the relative expression of the auxiliary subunit and the resulting stoichiometry of the channel complex.
KCNQ1 电压门控钾通道及其辅助亚基 KCNE1 在调节心跳方面起着至关重要的作用。KCNQ1 和 KCNE1 复合物的计量比一直存在争议，一些结果表明，形成通道的四个 KCNQ1 亚基与两个 KCNE1 亚基（4:2 计量比）相关联，而其他结果则表明计量比可能不固定。我们应用单分子荧光漂白法对许多单个复合物中的亚基进行计数，发现 KCNQ1-KCNE1 复合物的计量比是灵活的，多达四个 KCNE1 亚基与通道的四个 KCNQ1 亚基（4:4 计量比）相关联。发现各种计量比的比例取决于 KCNQ1 和 KCNE1 的相对表达密度。引人注目的是，门控的电压依赖性和动力学都取决于 KCNQ1 和 KCNE1 的相对密度，这表明心脏节律可能受到辅助亚基的相对表达和通道复合物的相应计量比的调节。
