COMPARATIVE PHYSIOLOGY OF MEMBRANE TRANSPORT

因此，研究其生理生化机制是十分必要的 膜运输使用比较和进化的方法。 我们 假设最早的细胞利用“质子经济”（主要 质子泵产生质子梯度， 质子-底物共输运和其它过程）。 在进化后期， “钠经济”发展起来， 动物细胞 建议比较共运输系统， 质子（E.利用钠离子共转运 （E. coli）。 此外，我们计划研究一个 代表使用以下任一种技术的中间类别的运营商 质子或钠用于共转运（E. coli）。 突变体 将被分离，其显示糖特异性或阳离子的变化， 识别. 我们打算克隆每种运输工具的突变基因 通过桑格双脱氧核苷酸测定DNA序列 法 比较改变的氨基酸序列的 载体蛋白和运输生理学的改变将有助于 将三维结构与功能联系起来。 第二个项目涉及细胞的比较生理学研究， 音量调节 与动物细胞一样，微生物没有细胞壁 (such如鸡毒枝原体）必须不断泵出氯化钠， 由于胶体渗透和唐南效应而扩散到细胞中的水 力. 建议研究NaCl的离子机理 从M.并与兽用抗菌药物进行了比较 细胞

It is proposed to study the physiological and biochemical mechanism of membrane transport using a comparative and evolutionary approach. We postulate that the earliest cell utilized a "proton economy" (primary proton pumps generated a proton gradient which was used for proton-substrate cotransport and other processes). Later in evolution a "sodium economy" developed and found its most sophisticated expression in animal cells. It is proposed to compare cotransport systems utilizing protons (lactose carrier of E. coli) with cotransport utilizing sodium ion (proline carrier of E. coli). In addition we plan to study a representative of the intermediate class of carriers that utilize either protons or sodium for cotransport (melibiose carrier of E. coli). Mutants will be isolated which show changes in sugar specificity or catiom recognition. We intend to clone the mutant gene for each of the transport proteins and determine the DNA sequence by the Sanger dideoxynucleotide method. A comparison between the altered amino acid sequence of the carrier protein and the altered physiology of transport will help to correlate three dimensional structure with function. A second project involves a study of the comparative physiology of cell volume regulation. As with animal cells microorganisms without cell walls (such as Mycoplasma gallisepticum) must continuously pump out the NaCl and water that diffuse into the cell as a result of colloid osmotic and Donnan forces. It is proposed to investigate the ionic mechanism for NaCl extrusion from M. gallisepticum and compare it with that used by animal cells.