ACTIVE TRANSPORT OF MALTOSE IN ESCHERICHIA COLI

所有活细胞的膜都含有特定的运输蛋白， 使细胞积累营养物质，并维持适当的 离子的浓度梯度。我们将研究它的结构和功能 一个特定的主动交通系统，以获得一些了解 这一过程是如何发生的。 将要研究的运输系统是麦芽糖/麦芽糊精 大肠杆菌的转运系统。该系统由五个部分组成 使细胞能够主动泵送麦芽糖和更长时间的蛋白质亚基 葡萄糖聚合物(麦芽糊精)进入细胞质。 我们将使用生化技术来定位与之相互作用的部位 底物分子。此外，我们将使用特定的标签来定位 供能者与系统交互的位置(S)。终于 我们将定义水溶性麦芽糖结合的位置 蛋白质与该系统的膜结合成分相互作用。 我们还将使用遗传方法来补充这些生化 实验。我们将分离底物专一性改变的突变体 从基因上定位底物识别位点。此外，我们还将 分离突变体，在突变体中，膜蛋白与 麦芽糖结合蛋白已经改变。我们将确定 对这些突变进行DNA测序，并将突变序列与 已知的野生型序列。 我们的长期目标是生成一幅底物分子如何 在转位过程中与蛋白质相互作用 以及这个过程是如何与能量耦合的。

The membranes of all living cells contain specific transport proteins that enable the cell to accumulate nutrients and to maintain appropriate concentration gradients of ions. We will study the structure and function of a specific active transport system in order to gain some understanding of how this process occurs. The transport system that will be studied is the maltose/maltodextrin transport system of Escherichia coli. This system is composed of five protein subunits which enable the cell to actively pump maltose and longer polymers of glucose (maltodextrins) into the cytoplasm. We will use biochemical techniques to localize the sites that interact with substrate molecules. In addition we will use specific labels for locating the site(s) at which the energy donor interacts with the system. Finally we will define the location at which the water soluble maltose binding protein interacts with the membrane bound components of the system. We will also use a genetic approach to complement these biochemical experiments. We will isolate mutants with altered substrate specificity to localize the substrate recognition site genetically. In addition we will isolate mutants in which the interaction of the membrane proteins with maltose binding protein has been altered. We will determine the sites of these mutations by DNA sequencing and comparing the mutant sequence with the known wild-type sequence. Our long term goal is to generate a picture of how substrate molecules interact with the proteins during the process of translocation through the membrane and how this process is coupled to energy.