Mechanisms of Ion Selectivity in Cloned Potassium Channels

克隆钾通道的离子选择性机制

• 批准号: 9807941
• 负责人: Stephen Korn
• 金额: $ 24.5万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9807941&HistoricalAwards=false
• 关键词: Mechanisms; Ion; Selectivity; Cloned; Potassium

IBN 98-07941 KORN Heart, brain, endocrine and muscle cells are called excitable cells, and rely on the precisely coordinated action of many ion channels for their function. These channels in the plasma membrane of the cell open and close in response to physiological stimulation, and allow the flux of ions into or out of the cell. Flux of calcium and sodium ions through their respective channels tends to subserve excitatory functions, and flux of potassium through potassium channels underlies many inhibitory functions. Although control of excitable behavior is extremely complex, the magnitude and time-course of potassium flux through potassium channels is often a critical factor in determining the duration of excitatory events. There are many different potassium channels, with subtly different structures. This subtle structural variation among channels results in a large degree of functional diversity. Both the magnitude and time-course of potassium channel activity is sensitive to the concentration of potassium and sodium ion in the extracellular space (the region just outside of a cell), and this sensitivity also varies among channels. Two potassium binding sites have been functionally isolated, a low affinity site that underlies some channel functions and a high affinity site that underlies others. In particular, the high affinity site, located at the "selectivity filter," underlies the ability of potassium to prevent sodium from passing through the cell. The low affinity site is not involved in selectivity but is involved in several other channel functions. Recent structural studies have identified the molecular location of the selectivity filter, and the associated high affinity site(s). These studies were unable to identify a cation binding site external the site of selectivity. Consequently, either one of these putative high affinity sites contributes to the low affinity site functions or there is an as yet unknown cation binding site, external to the st ructurally described sites, which cannot be observed in structural studies. The primary focus of these studies will be to determine whether the structurally described selectivity filter site(s) interconvert between low affinity and high affinity sites, or whether a low affinity site exists external to and independent from the high affinity site. The studies will combine molecular biological techniques with electrophysiological recordings and biophysical analysis to determine whether the different functionally- identified binding sites are structurally distinct. Results from this project will enhance our understanding of the nature of cation binding sites in the channel pore, and will thus enhance our knowledge of the molecular mechanisms that underlie phenotypic diversity in potassium channels.

IBN 98-07941 Korn心脏、脑、内分泌和肌肉细胞被称为可兴奋细胞，它们的功能依赖于许多离子通道的精确协调作用。细胞质膜中的这些通道响应生理刺激而打开和关闭，并允许离子流入或流出细胞。钙离子和钠离子通过各自通道的流量往往削弱兴奋功能，而钾离子通道的流量则是许多抑制功能的基础。虽然兴奋性行为的控制非常复杂，但钾通道中钾离子流量的大小和时间过程往往是决定兴奋性事件持续时间的关键因素。有许多不同的钾通道，具有微妙的不同结构。渠道之间这种微妙的结构差异导致了很大程度的功能多样性。钾通道活动的大小和时间过程都对细胞外空间(细胞外区域)中钾离子和钠离子的浓度敏感，这种敏感性在不同的通道中也是不同的。已经从功能上分离了两个钾结合位点，一个是一些通道功能的低亲和力部位，另一个是另一些通道功能的高亲和力部位。特别是，位于“选择性过滤器”的高亲和力部位，是钾阻止钠通过细胞的能力的基础。低亲和力位点不参与选择性，但参与其他几种通道功能。最近的结构研究已经确定了选择性过滤器的分子位置和相关的高亲和力位点(S)。这些研究无法确定选择性部位外的阳离子结合部位。因此，要么是这些假定的高亲和力位点中的一个参与了低亲和力位点的功能，要么是在结构描述的位点之外存在着一个未知的阳离子结合位点，这在结构研究中是无法观察到的。这些研究的主要焦点将是确定结构上描述的选择性过滤位点(S)是否在低亲和力和高亲和力位点之间相互转换，或者是否存在位于高亲和力位点外部且独立于高亲和力位点的低亲和力位点。这些研究将结合分子生物学技术、电生理记录和生物物理分析来确定不同功能识别的结合位点是否在结构上是不同的。这个项目的结果将加深我们对通道孔中阳离子结合部位的性质的理解，从而增强我们对钾通道表型多样性的分子机制的了解。