REGULATION OF THE MAJOR OUTER MEMBRANE PORIN PROTEINS

肠道细菌产生一组蛋白质，称为孔蛋白，它能起作用 作为被动扩散孔，允许小的亲水性分子 穿过外膜通透性屏障。大肠杆菌 K12含有两种主要的、非特异性的孔蛋白：OmpF和OMPC。在……里面 一般情况下，细胞中存在的这两种蛋白的总量 是不变的。然而，相对水平会因此而波动 以适应各种环境条件。一个环境因素 这一点似乎特别重要，那就是媒体的渗透。如果 渗透压高，以OMPC为主。相反，在稀释的情况下 Media，找到了OmpF。据认为，通过感知渗透压， 大肠杆菌可以区分其常见的栖息地，即内部或 在宿主动物之外。我们希望了解分子 这是这一监管制度的基础。 我们实验室之前的工作已经确定了两个基因，ompR和envZ， 它们指定了激活孔蛋白基因所需的蛋白质 表情。EnvZ似乎具有膜结合信号的功能 传感器，用于监测环境并指导效应器 蛋白，OmpR(一种DNA结合蛋白)与适当的顺式作用 在OmpF和OMPC发起人的网站上。OmpR和EnvZ共享 与其他细菌的感受器和效应器蛋白有显著同源性 存在于各种生物体中的双组分调控系统。 OmpR的结构和功能将通过一个 70ompR的详细遗传和生化特征 导致多种孔蛋白表型的错义突变。 所获得的结果应该会澄清遗传开关的性质 控制毛孔的波动，并为每一个 OmpF和OMPC启动子上的多个顺式作用位点。 更多的实验试图验证 OmpR与RNA聚合酶α亚基的相互作用 来探索它的机械含义。这些研究针对的是 关于积极激活剂，如OmpR，如何发挥作用的问题 刺激转录。最后，进行了详细的遗传分析 计划中的EnvZ类似于我们的 OmpR的遗传分析。这一分析的目标是获得 洞察EnvZ的感官功能及其作用方式 从机械上来说，它是一种信号转换器，可以触发基因开关。

Enteric bacteria produce a set of proteins, termed porins, that act as passive diffusion pores to allow small hydrophilic molecules to cross the outer membrane permeability barrier. Escherichia coli K12 contains two major, non-specific porins, OmpF and OmpC. In general, the total amount of these two porins present in the cell is constant. However, the relative levels fluctuate in response to a variety of environmental conditions. One environmental factor that appears to be particularly important is media osmolarity. If osmolarity is high, OmpC predominates. Conversely, in dilute media, OmpF is found. It is thought that by sensing osmolarity, E. coli can distinguish its common habitats, i.e., inside or outside of a host animal. We wish to understand the molecular basis for this regulatory system. Previous work from our lab has identified two genes, ompR and envZ, which specify proteins that are required to activate porin gene expression. EnvZ appears to function as a membrane-bound signal transducer to monitor the environment and direct the effector protein, OmpR (a DNA-binding protein) to the appropriate cis-acting sites at the ompF and ompC promoters. OmpR and EnvZ share significant homology with the sensor and effector proteins of other two-component regulatory systems found in a variety of organisms. The structure and function of OmpR will be probed through a detailed genetic and biochemical characterization of 70 ompR missense mutations which confer a variety of porin phenotypes. Results obtained should clarify the nature of the genetic switch that controls porin fluctuation and assign roles to each of the multiple cis-acting sites at the ompF and ompC promoters. Additional experiments seek to verify the existence of an interaction between OmpR and the a subunit of RNA polymerase and to probe its mechanistic implications. These studies address the question of how positive activators, such as OmpR, function to stimulate transcription. Lastly, a detailed genetic analysis of envZ is planned which is similar to, and will complement, our genetic analysis of ompR. The goal of this analysis is to gain insights into the sensory functions of EnvZ and how it acts mechanistically as a signal transducer to throw the genetic switch.