ACTIVE TRANSPORT OF MALTOSE IN ESCHERICHIA COLI

所有活细胞的细胞膜都含有特定的转运蛋白， 使细胞能够积累营养，并保持适当的 离子的浓度梯度。 我们将研究它的结构和功能 一个特定的主动运输系统，以获得一些了解 这个过程是如何发生的。 将要研究的转运系统是麦芽糖/麦芽糖糊精 大肠杆菌的转运系统。 该系统由五个 蛋白质亚基，使细胞能够积极泵麦芽糖和更长的时间 葡萄糖聚合物（麦芽糖糊精）进入细胞质。 我们将使用生物化学技术来定位与之相互作用的位点， 底物分子 此外，我们将使用特定的标签来定位 能量供体与系统相互作用的位点。 最后 我们将定义水溶性麦芽糖结合的位置 蛋白质与系统的膜结合组分相互作用。 我们还将使用遗传学方法来补充这些生化 实验 我们将分离出底物特异性改变的突变体， 在基因上定位底物识别位点。 此外，我们将 分离突变体，其中膜蛋白与 麦芽糖结合蛋白发生了改变 我们将确定 这些突变通过DNA测序和比较突变序列与 已知的野生型序列 我们的长期目标是绘制出一幅图像， 与蛋白质相互作用的过程中易位通过 膜以及这个过程如何与能量耦合。

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.