MOLECULAR BIOPHYSICS OF POTASSIUM CHANNEL INACTIVATIONS

失活是分子记忆的一种形式， 大多数钾离子通道 时间进程可以从缓慢 （秒）到超快，因为可以恢复;而多个分子 已经确定了机制，那些潜在的失活， 心脏中的钾通道仍然不完全清楚。 该项目将建立在我们开发的初步数据基础上， 测试这些机制的假设。 我们发现 Kv1.4的N-末端链中的二级结构是 它被一个~球和链~灭活的关键决定因素 机制在具体目标1中，我们将使用基于结构的 删除策略来测试Kv4.3的假设，最近- 被鉴定为人类伊藤的主要成分， 类似的机制。在具体目标2中， 离子流修饰通道的荧光成像 测量将用于测试假设，恢复 从失活开始由S4的运动。 我们有 鉴定了N-末端的超快速失活形式， Kv1.4的突变体。 在具体目标3中，我们将检验该假设 这种形式的超快速失活也发生在Kv4.3中， 在Ikr α亚单位HERG中。 此外，这些突变体 通道将被用来测试的假设，增强 预先存在的灭活过程（而不是球和链 钾离子通道β- 亚单位。 通过阐明失活机制的范围 存在于心脏钾通道中，这些实验将 进一步了解了决定性因素， 健康人心脏电生理的异质性 和疾病

Inactivation is a form of molecular memory that is common to most potassium channels. The time course can range from slow (seconds) to ultra-fast, as can recovery; while multiple molecular mechanisms have been identified, those underlying inactivation of potassium channels in the heart remain incompletely understood. This Project will build on preliminary data we have developed to test hypotheses with respect to these mechanisms. We have found that secondary structure in the N-terminus chain of Kv1.4 is an crucial determinant of its inactivation by a ~ball-and-chain~ mechanism. In Specific Aim 1, we will use a structure-based deletion strategy to test the hypothesis that Kv4.3, recently- identified as a major component of human Ito, inactivates by similar mechanisms. In Specific Aim 2, experiments combining fluorescent imaging of modified channels with ion current measurements will be used to test the hypothesis that recovery from inactivation is initiated by movement of S4. We have identified a form of ultra-rapid inactivation in an N-terminus mutant of Kv1.4. In Specific Aim 3, we will test the hypothesis that this form of ultra-rapid inactivation also occurs in Kv4.3 and in the Ikr alpha-subunit, HERG. In addition, these mutant channels will be used to test the hypothesis that enhancement of pre-existing inactivation processes (rather than a ball-and-chain mechanism) underlies the effect of potassium channel beta- subunits. By elucidating the range of inactivation mechanisms present in cardia potassium channels, these experiments will provide further understanding of the determinants of the heterogeneous electrophysiologic behavior of the heart in health and disease.