The Structure and Gating of the Epithelial Na+ Channel

上皮Na通道的结构和门控

• 批准号: 6738265
• 负责人: OSSAMA B KASHLAN
• 金额: $ 4.3万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6738265
• 关键词: Xenopus; Xenopus oocyte; allosteric site; binding sites; conformation; microinjections; physical model; postdoctoral investigator; protein folding; protein protein interaction; protein structure function; site directed mutagenesis; sodium channel; voltage /patch clamp

DESCRIPTION (provided by applicant): Epithelial Na+ Channel (ENaC) activity can be modulated by two distinct mechanisms: either by changes in single channel gating properties (i.e., open probability), or by changes in the number of channels expressed in the apical membrane. The mechanism for ENaC gating has yet to be determined. Based on analogy with other cation channels, several mechanisms have been proposed. These mechanisms generally fall into two categories, either channel blocking, or an allosteric transition. In the channel-blocking hypothesis, either a portion of ENaC itself, or another molecule inserts into the channel pore, preventing Na+ transfer. In this hypothesis, changes in residue contacts as the channel transitions from an open to a closed state would be localized to the area, which interacts with the blocker. In the allosteric transition hypothesis, the helices, which form the pore, would undergo a conformational change such that Na+ could no longer traverse the pore. External stimuli could induce such a transition by causing small local changes, which could propogate into global changes, driving the allosteric transition. In this hypothesis, changes in residue contacts as the channel transitions from an open to a closed state would be widespread. We hypothesize that residue contacts made within the pore region of ENaC are altered in the open vs. the closed conformation of the channel. In order to assess these changes, we will exploit the ability of Ni2+ to selectively bind histidine to generate a map of pore region residues. Such a map will help to delineate which amongst the currently proposed models for ENaC gating is most likely

描述（由申请人提供）：上皮Na+通道（ENaC）活性可以通过两种不同的机制调节：通过改变单通道门控特性（即打开概率），或通过改变顶端膜中表达的通道数量。ENaC门控的机制尚未确定。基于与其他阳离子通道的类比，提出了几种机理。这些机制一般分为两类，要么是通道阻塞，要么是变构转变。在通道阻断假说中，ENaC本身的一部分或另一个分子插入通道孔中，阻止Na+转移。在这个假设中，当通道从打开状态转变为关闭状态时，残馀接触的变化将局限于与阻滞剂相互作用的区域。在变构转变假说中，形成孔洞的螺旋会发生构象变化，使得Na+不能再穿过孔洞。外部刺激可以通过引起微小的局部变化来诱导这种转变，这些变化可以传播为全球变化，从而推动变构转变。在这个假设中，当通道从打开状态转变为关闭状态时，剩余接触的变化将是普遍的。我们假设在ENaC的孔隙区域内产生的残留接触在通道的开放构象和封闭构象中发生了变化。为了评估这些变化，我们将利用Ni2+选择性结合组氨酸的能力来生成孔区残基图。这样的地图将有助于描述在目前提出的ENaC门控模型中哪一个是最有可能的