REGULATION OF ION CHANNELS BY METHIONINE OXIDATION

描述：先前的研究表明，像许多其他蛋白质一样， 钾通道的氨基酸残基会被氧化 活性氧物种。氨基酸残基的氧化，尤其是 半胱氨酸残留物，已经有了很好的记录。蛋氨酸很容易被氧化 形成甲硫氨酸亚硫醚。蛋氨酸的氧化是独特的，因为它 是可逆的，氧化蛋氨酸的还原需要一种酶， 蛋氨酸亚砜还原酶(MSRA)。蛋氨酸的可逆性 MSRA催化的氧化反应表明，它可能是一种重要的 细胞调控机制。初步结果确实表明， Shaker钾通道中蛋氨酸残基的氧化作用非常显著 对通道激活和失活的影响。这个项目将 确立蛋氨酸氧化的动态功能作用为关键 参与细胞兴奋性的调节。振荡型钾通道 将在非洲爪哇卵母细胞中表达，其宏观和 使用双电极电压检测单通道电流特性 钳制和膜片钳制方法。蛋氨酸突变与MSRA的作用 共表达将被定量检测以阐明生物物理 涉及的机制。蛋氨酸氧化及其逆转的重要性 MSRA在其他多种钾通道中的作用及电压依赖性 还将检查钙通道。拟议研究的结果 将建立一种新的细胞兴奋性机制，涉及蛋氨酸 氧化和还原。

DESCRIPTION: Previous studies have shown that, like many other proteins, amino acid residues of potassium channels are subject to oxidation by reactive oxyge species. Oxidation of amino acid residues, especially of cysteine residues, is well documented. Methionine can be readily oxidized to form methionine sulfoxide. Oxidation of methionine is unique in that it is reversible and that reduction of oxidized methionine requires an enzyme, methionine sulfoxide reductase (MsrA). The reversibility of methionine oxidation catalyzed by MsrA suggests that it could act as an important cellular regulatory mechanism. Preliminary results indeed suggest that oxidation of methionine residues in Shaker potassium channels has dramatic effects on the channel activation and deactivation. This project will establish the dynamic functional role of methionine oxidation as a key player in regulation of cellular excitability. Shaker potassium channels will be expressed in Xenopus oocytes and their macroscopic and single-channel current properties examined using the two-electrode voltage clamp and patch-clamp methods. The effects of methionine mutations and MsrA co-expression will be quantitatively assayed to elucidate the biophysical mechanisms involved. The importance of methionine oxidation an its reversal by MsrA in a variety of other potassium channels and voltage-dependent calcium channels will also be examined. Results from the proposed research will establish a novel cellular excitability mechanism involving methionine oxidation and reduction.