BIOCHEMICAL COMPONENTS OF A TRANSPORT SYSTEM

甲基半乳糖苷通透酶（MeGalP）是一种多组分转运酶， 大肠杆菌K-12介导细胞内 D-半乳糖和密切相关的糖的积累。 系统 需要mglA、mglB和mglC三个基因进行转运。 mglB基因 编码一种周质半乳糖结合蛋白， 高亲和力转运。 控制MegalP的三个基因最近已被克隆， 定位在4.6kb的DNA片段上。 利用基因扩增技术， mglA和mglC的产物已被鉴定为膜蛋白， 52，000（52 K）和38，000（38 K）道尔顿表观分子量， 分别 52 K蛋白已被分离、纯化并用于 在小鼠和兔子体内引发特异性抗体。 我们建议大规模制备纯化的38 K和52 K蛋白， 随后研究其性能。 此外，我们还计划进行实验 旨在建立膜之间的功能关系， 蛋白质和半乳糖结合蛋白。 mglB. 为了促进这些 本实验拟建立52 K蛋白的放射免疫分析方法。 另一个目的是测序整个mgl操纵子DNA。 长期 目的是充分了解糖的分子机制 跨细胞膜运输。 这一目标与健康直接相关 因为几乎所有的细胞都依赖于糖的摄取来进行代谢 能源和结构维护。

The methylgalactoside permease (MeGalP) is a multicomponent transport system of Escherichia coli K-12 which mediates the intracellular accumulation of D-galactose and closely related sugars. The system requires three genes, mglA, mglB and mglC, for transport. The mglB gene codes for a periplasmic galactose-binding protein which is necessary for high affinity transport. The three genes controlling MegalP have been recently cloned and physically mapped on a 4.6-kb DNA fragment. Using gene amplification techniques, the products of mglA and mglC have been identified as membrane proteins of 52,000 (52K) and 38,000 (38K) daltons apparent molecular weight, respectively. The 52K protein has been isolated, purified, and used to elicit specific antibodies in mice and rabbits. We propose large scale preparation of purified 38K and 52K proteins for subsequent study of their properties. In addition, we plan experiments designed to establish functional relationships between the membrane proteins and the galactose-binding protein. mglB. To facilitate these experiements, we plan to develop a radioimmunoassay for the 52K protein. Another aim is to sequence the entire mgl operon DNA. The long-term objective is to fully understand the molecular mechanisms underlying sugar transport across cell membranes. This aim is directly related to health problems since practically all cells depend on sugar uptake for metabolic energy and structural maintenance.