"Low Energy Shock in E. coli"

点击翻译按钮获取中文摘要

Lewis 9317013 Addition of uncouplers to E. coli causes a low energy shock response that is accompanied by induction of multidrug resistance pumps. A Summary of the objectives aimed at identifying the components of the response and understanding their interactions is given below. 1. Expression of a target gene. Regulatory mutations in emrD, a multidrug resistance gene, that lead to constitutive expression will be used to determine the upstream site controlling uncoupler- dependent expression. 2. The signal. Expression of emrD in an ATPase mutant in response to an uncoupler will be measured to determine whether the signal originates prior to, or after ATP synthesis. Changes in pmf will be measured in parallel to determine the quantitative requirements for the inducing signal. 3. The sensor. Regulatory mutations leading to constitutive expression of emrD will be used to clone the regulator genes. It is expected that one of the genes will code for the receptor that senses uncoupling. 4. Are other MDR's target genes of low energy shock? Five more putative MDR's have been found in E. coli. the possibility that they are also induced by uncoupling will be studied using Northern blotting. Significance: it is of general importance in understanding cell metabolism to learn how the cell senses its energy status and activates a response mechanism. %%% Cells obtain energy through respiration. This is a process of oxidation of various nutrients such as sugars by oxygen. Respiration takes place in the cell membrane. The energy released in the course of respiration is stored in the form of a "high energy" molecule, ATP. A large number of toxic substances affects the membrane and leads to an "Energy Shock", or loss of energy- producing capability. We found that the cell responds to such toxins by inducing the synthesis of a special class of proteins, multiple drug resistance pumps, that extrude the toxins from the cell. How does a cell sense the presence of t oxins? What is the mechanism for the induction of the multidrug resistance pumps? These are the questions that will be studied in this project. ***