MOLECULAR MECHANISMS IN ANION TRANSPORT

阴离子运输的分子机制

• 批准号: 2609215
• 负责人: ROBERT B GUNN
• 金额: $ 43.67万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1981
• 资助国家: 美国
• 起止时间: 1981-09-01 至 1999-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2609215
• 关键词: Xenopus; alternatives to animals in research; anions; antiport; band 3 protein; cations; cell membrane; chemical binding; chlorine; conformation; dogs; erythrocyte membrane; erythrocytes; human tissue; hydrogen; ion transport; laboratory rabbit; mathematical model; membrane activity; membrane model; membrane permeability; membrane structure; membrane transport proteins; protein folding; protein structure; protein structure function; site directed mutagenesis; sulfates

The objective of this proposal is to elucidate the mechanisms of anion exchange and proton-anion cotransport by the band 3 transporter of human erythrocytes. The mediated exchange of chloride and bicarbonate is essential for efficient removal of CO2 and metabolic protons from tissues and appears to be rate-limiting for CO2 excretion in the lungs during severe exercise. Cotransport of small molecules is important in epithelial membranes and volume regulation by cells. We propose 1) to characterize the net flux of proton equivalents across red cells in order to test the relationships between these two functions on band 3; 2) to characterize inhibitor interactions with the anion transporter which will test the topology of the sites and determine the conformations of the transporter that permit binding; and 3) to develop and test a new working hypothesis for the mechanisms of anion and proton transport. In the newly proposed mechanism each band 3 monomer has a single proton transport site and a single anion transport site which do not always have access to the same side of the membrane at the same time. This asynchronous behavior of these two transport sites, for which there is already evidence, results in equations for the transport velocity that exhibit 1) self-inhibition on each side of the membrane at high anion concentrations; 2) sigmoid activation kinetics for monovalent anions at low pH; 3) inhibition of proton-sulfate cotransport self-exchange at low pH; 4) the relationships between anion exchange and proton-anion (H + SO4 and H + Cl) cotransport; and 5) an explanation for residual transport after irreversible inhibition with phenylglyoxal. None of these characteristics have been so simply explained before. These studies involve measurements of net fluxes and tracer exchange across human red cell membranes, development of computer methods for non-numerical functional analysis of reaction velocities, and ligand binding to functional transmembrane proteins as probes for conformational analysis. These studies will both extend our knowledge of chloride-bicarbonate exchange and develop new analytical tools for the study of cotransport mechanisms and functional protein conformations.

该提议的目的是阐明阴离子的机制 人类带3运输蛋白的交换和质子 - 氨基 红细胞。 介导的氯化物和碳酸氢盐交换为 从组织中有效去除二氧化碳和代谢质子至关重要 并且在肺部似乎是肺中二氧化碳排泄的速率限制。 严重的运动。 小分子的共转运在上皮很重要 细胞对膜和体积调节。 我们建议1）表征 跨红细胞的质子当量的净通量，以测试 这两个功能在频段3上之间的关系； 2）表征 抑制剂与阴离子转运蛋白的相互作用将测试 站点的拓扑并确定转运蛋白的构象 允许约束； 3）开发和检验一个新的工作假设 用于阴离子和质子转运的机制。 在新提议中 机构每个频段3单体具有一个单质子传输位点和A 单个阴离子运输站点，不一定总是可以访问相同 膜的一侧同时。 这些的这种异步行为 已经有证据的两个运输地点导致 展示的传输速度方程1）自我抑制 膜的每一侧高阴离子浓度； 2）乙状结肠 低pH值的单价阴离子的激活动力学； 3）抑制 低pH值的质子硫酸盐共转移自我交换； 4）关系 在阴离子交换和质子大茴香（H + SO4和H + Cl）之间之间的共晶； 5）解释不可逆抑制后残留运输 与苯基糖。 这些特征都没有那么简单 以前解释过。 这些研究涉及测量净通量和 横跨人类红细胞膜的示踪剂交换，计算机的开发 反应速度的非数字功能分析的方法， 配体与功能跨膜蛋白的结合作为探针 构象分析。 这些研究都将扩展我们对 氯化物 - 双碳酸盐交换并开发新的分析工具 研究机制和功能蛋白构象的研究。