PROTEIN STRUCTURE-FUNCTION IN GASTRIC MICROBIAL PATHOGENESIS

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。幽门螺杆菌、弯曲杆菌等多种病原菌。而炭疽杆菌可以通过胃的高度酸性环境入侵宿主，从而导致人类严重甚至致命的疾病状态。虽然单个微生物用来在这种恶劣环境中生存的后殖民防御机制可能是众所周知的，但目前还不清楚这些微生物如何度过建立有利于疾病的条件所需的‘过境时间’。事实上，众所周知，有几种微生物可以通过短暂暴露在pH值为4.0的盐酸中而被杀死。在运输过程中，蛋白质可能会长时间暴露在富含盐酸的酸性环境中，这些条件足以使许多蛋白质失活。这就提出了一个问题，即这些微生物如何在不一定受益于“预孵化”的情况下存活下来，而‘预孵化’通常是强大的耐酸反应所必需的。这项研究的长期目标是研究蛋白质在高度酸性环境中保持生物活性的机制。我们建议使用硫杆菌属的周质氧化还原蛋白系统作为模型系统来研究低pH环境下蛋白质的结构-功能和稳定性。我们选择这个模型是因为：1)它避免了直接与病原体合作的需要，2)硫杆菌属中的几个物种能够在pH低至0.8的范围内生长，3)氧化还原反应提供了容易的生物活性测定，以及4)硫杆菌在含硫底物上生长所经历的条件很好地代表了胃环境的pH。因此，在这项研究中获得的信息应该直接适用于致病物种。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A number of pathogens such as H. pylori, Campylobacter sp. and Bacillus anthracis can cause serious and even lethal disease states in humans by invading the host through the highly acidic environment of the stomach. While the post-colonization defense mechanism used by individual microorganisms to survive this hostile environment may be known well characterized, it is not as clear how the organisms survive the 'transit time' necessary to establish those conditions favorable to disease. Indeed, it is well known that several of the microorganisms can be killed by brief exposure to HCl at pH ? 4.0. During the transit time, proteins could be exposed to an HCl rich, acidic environment for significant periods of time These conditions are more than sufficient to inactivate many proteins. This raises the question as to how these organisms survive the transit time without necessarily benefiting from 'pre-incubations' that are normally required for a strong acid tolerance response. Long-term goals of the research are to study the mechanism by which proteins maintain their biological activity in highly acidic environments. We propose to use the periplasmic redox protein systems of the genus Thiobacillus as a model system to study protein structure-function and stability in low pH environments. We choose this model because; 1) it avoids the need to work directly with pathogens, 2) several species within the Thiobacillus genus are capable of growth at pH ranging as low as 0.8, 3) the redox reactions offer easy to assay biological activities, and 4) the conditions experienced by the thiobacilli during growth on sulfur containing substrates are a good representation of the pH of the gastric environment. Hence the information gained in this study should be directly applicable to the pathogenic species.