MECHANISM OF CHLORIDE TRANSPORT BY HALORHODOPSIN

我们将探讨盐视紫红质作为一种 光驱动的产电氯化物泵。 这个氯化物运输系统 在盐细菌的细胞质膜中发现，是视网膜色素 其发色团表现出闪光诱导的吸光度变化， 氯化物的存在。 此外，氯离子以及其他阴离子， 明显影响视网膜席夫碱的pK。 研究这些 更详细的现象，并使用特定的标签来修改选定的 氨基酸残基，我们将描述参与结合的基团， 氯化物，氯化物结合位点的数量及其与 以及质子化/去质子化的作用， 氯离子易位 我们会特别注意 盐视紫红质含有巯基， 色素的光化学。 虽然纯化的色素蛋白 （表观分子量21 kDa）的盐视紫红质结合氯离子，和 显示了在完整系统中观察到的氯化物依赖性效应，我们 将搜索和识别任何其他迄今未知的组件， 盐视紫红质 在这项研究中，我们希望建立一个基础， 光化学变化的分子机制模型 与氯离子逆着电化学梯度迁移有关。 这样的模型应该有助于理解离子泵， 将军

We will explore the mechanism by which halorhodopsin functions as a light-driven electrogenic chloride pump. This chloride-transport system, found in the cytoplasmic membrane of halobacteria, is a retinal pigment whose chromophore exhibits flash-induced absorbance changes dependent on the presence of chloride. Furthermore, chloride, as well as other anions, apparently influences the pK of the retinal Schiff's base. Studying these phenomena in more detail, and using specific labels to modify selected amino acid residues, we will describe the groups involved in the binding of chloride, the number of chloride-binding sites and their relationship to one another, and the role of protonation/deprotonation of groups in the chloride translocation. Special attention will be paid to the possibility that halorhodopsin contains a sulfhydryl group with an influence on the photochemistry of the pigment. Although the purified chromoprotein (apparent molecular weight 21 kDa) of halorhodopsin binds chloride, and shows the chloride-dependent effects observed with the intact system, we will search for and identify any other, so far unknown, components of halorhodopsin. In this study we expect to establish the basis for a first model of the molecular mechanism of how the photochemical changes are related to chloride translocation against an electrochemical gradient. Such a model should contribute to the understanding of ionic pumps in general.