PROTEIN STRUCTURE-FUNCTION IN GASTRIC MICROBIAL PATHOGENESIS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。许多病原体，如幽门螺杆菌、弯曲杆菌和炭疽芽孢杆菌，可以通过胃的高酸性环境侵入宿主，导致人类严重甚至致命的疾病状态。虽然个体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特征，但尚不清楚微生物如何在建立有利于疾病的条件所必需的“过渡时间”中存活下来。事实上，众所周知，一些微生物可以通过短暂暴露于pH ？4.0. 在运输过程中，蛋白质可能暴露在富含HCl的酸性环境中很长一段时间，这些条件足以使许多蛋白质失活。这就提出了一个问题，即这些生物如何在运输时间内存活下来，而不一定受益于强耐酸反应通常需要的“预孵育”。该研究的长期目标是研究蛋白质在高酸性环境中维持其生物活性的机制。我们建议使用硫杆菌属的质周氧化还原蛋白系统作为模型系统来研究蛋白质在低pH环境下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打交道的需要，2)硫杆菌属中的一些物种能够在低至0.8的pH范围内生长，3)氧化还原反应提供了易于测定的生物活性，以及4)硫杆菌在含硫底物上生长时所经历的条件很好地代表了胃环境的pH。因此，本研究获得的信息应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.