BIOCHEMISTRY OF BACTERIAL CELL MEMBRANES

生物膜最基本的性质是作为一种 选择性屏障，只允许渗透某些特定的溶质 上课。这些功能的结构基础将通过以下方式进行调查 使用了几个来自细菌的实验系统。(1)外膜， 位于肽聚糖层和胞质膜外 革兰氏阴性菌是研究这一现象的理想模型膜 类型，因为它的功能非常简单，因为它主要允许 被动和便利的扩散过程。亲水性的扩散 溶质由孔蛋白和其他特定的通道介导，而 将对这些通道的属性进行表征。这些领域将是 重点将包括电压和压力中介的关闭 孔蛋白通道、假单胞菌中孔蛋白通道的识别和性质 铜绿假单胞菌，以及特定通道的功能架构，如 噬菌体的lambda受体(麦芽多糖)通道。此外，不同寻常的 需要TonB蛋白协作的特定运输系统 将使用一种新开发的测试方法进行研究。最后，分子 血管内皮细胞脂质双层区通透性异常低的基础 外膜将利用完整的细胞，平面双层， 和双层囊泡。这些研究的结果具有重大的医学意义。 感兴趣的是，因为大多数抗药性细菌病原体引起 医院获得性感染是一种被外膜覆盖的细菌 渗透率低。因此，他们可以提出更有效的生产方法 可以克服这一障碍的抗生素。(2)分枝杆菌细胞 WALL富含脂质成分，最近被证明是一种 非常有效的渗透性屏障。我们将研究亲水性如何 分子通过这一屏障扩散。如果类孔蛋白可以 识别和表征，这将再次建议如何改进 抗生素和化疗药物对这些细菌的渗透， 尤其是以抗生素著称的“非典型”分枝杆菌 耐药性及其引起难治性继发感染的能力 在许多艾滋病患者身上。(3)麦芽糖转运的分子机制 跨越细胞膜的大肠杆菌将被研究。这 系统之所以令人感兴趣，不仅是因为它是一个高度复杂和高效的 运输机械，也是它的组成部分，蛋白质共有很强的 与泵出抗癌药物的P-糖蛋白的序列同源性 从一些肿瘤细胞中分离出来。

The most fundamental property of biological membranes is to serve as a selective barrier, allowing the penetration of only solutes of certain classes. The structural basis of these functions will be investigated by using several experimental systems from bacteria. (1) The outer membrane, located outside the peptidoglycan layer and the cytoplasmic membrane of gram-negative bacteria, is an ideal model membrane for the study of this type, because its functions are very simple in that it allows mainly passive and facilitated diffusion processes. The diffusion of hydrophilic solutes are mediated by porin and other specific channels, and the properties of these channels will be characterized. Areas that will be emphasized will include the voltage- and pressure-mediated closing of the porin channel, the identity and properties of porin channels in Pseudomonas aeruginosa, and the functional architecture of specific channels such as the phage lambda receptor (maltoporin) channel. In addition, unusual specific transport systems that require the collaboration of TonB protein will be studied by using a newly developed assay. Finally, the molecular basis of the unusually low permeability of lipid bilayer region of the outer membrane will be studied by utilizing intact cells, planar bilayers, and bilayer vesicles. The results of these studies are of great medical interest, as most of the antibiotic-resistant bacterial pathogens causing hospital-acquired infections are bacteria covered with outer membranes of low permeability. They can thus suggest ways to produce more effective antibiotics that can overcome this barrier. (2) The mycobacterial cell wall is rich in lipidic constituents, and was recently shown to act as an extremely effective permeability barrier. We will study how hydrophilic molecules diffuse across this barrier. If porin-like proteins can be identified and characterized, this will again suggest ways of improving the penetration of antibiotics and chemotherapeutic agents into these bacteria, especially "atypical" mycobacteria well-known for their antibiotic resistance and their capability of causing intractable secondary infections in many AIDS patients. (3) The molecular mechanism of transport of maltose across the cytoplasmic membrane of Escherichia coli will be studied. This system is of interest not only because it is a highly complex and efficient transport machinery, but also its component proteins share a strong sequence homology with the P-glycoprotein that pumps out anti-cancer drugs from some of the tumor cells.