BIOCHEMISTRY OF BACTERIAL CELL MEMBRANES

生物膜最基本的特性是作为一种 选择性屏障，仅允许某些溶质渗透 班 这些功能的结构基础将通过以下方式进行研究： 使用了几种细菌实验系统。 (1)外膜， 位于肽聚糖层和细胞质膜外， 革兰氏阴性菌，是一种理想的模型膜，为研究这一点 类型，因为它的功能非常简单，主要允许 被动和易化扩散过程。 亲水扩散 溶质由孔蛋白和其他特定通道介导， 这些信道的特性将被表征。 将成为 强调的将包括电压和压力介导的关闭， 孔蛋白通道，假单胞菌孔蛋白通道的鉴定和性质 铜绿，和特定通道的功能结构， 噬菌体λ受体（麦芽孔蛋白）通道。 此外，不寻常的 需要TonB蛋白协作的特异性转运系统 将通过使用新开发的检测方法进行研究。 最后，分子 基于脂质双层区域的异常低渗透性， 外膜将通过利用完整细胞，平面双层， 和双层囊泡。 这些研究的结果具有很大的医学意义。 感兴趣，因为大多数耐药细菌病原体引起 医院获得性感染是细菌覆盖的外膜， 低渗透性 因此，他们可以建议如何生产更有效的 抗生素可以克服这一障碍。 (2)分枝杆菌细胞 墙是丰富的成分，最近被证明是作为一个 非常有效的渗透屏障。 我们将研究如何亲水 分子扩散穿过这个屏障。 如果孔蛋白样蛋白可以 确定和特点，这将再次建议如何改善 抗生素和化疗剂渗透到这些细菌中， 特别是以其抗生素而闻名的“非典型”分枝杆菌 耐药性及其引起难治性继发感染的能力 许多艾滋病患者。 (3)麦芽糖转运的分子机制 将研究大肠杆菌细胞质膜的跨膜作用。 这 系统之所以令人感兴趣，不仅是因为它是一种高度复杂和高效的 运输机械，而且它的组成蛋白质共享一个强大的 与泵出抗癌药物的P-糖蛋白序列同源 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.