Urea-dependent virulence in uropathogenic bacteria

说明(申请人提供：尿素酶，催化水解酶 尿素转化为氨和碳酸是由不同的细菌种类产生的 包括各种需氧菌、兼性厌氧菌和专性厌氧菌 革兰氏阴性和革兰氏阳性生物和物种一样，都是产生尿素酶的生物 分支杆菌和解脲支原体。尿素酶在毒力中起着重要作用 当由尿路、口腔和胃十二指肠病原体表达时。 普罗维登西亚和变形杆菌，两种最常见的解尿剂 尿路病原体，只有在尿素存在的情况下才能表现出黑色葡萄球菌。这种对尿素的依赖 表达是由UreR介导的，UreR是属于 监管机构的AraC家族。有证据表明，尿素直接与 因此是这种激活剂的效应器分子。尿素可在以下位置找到 尿路中的浓度最高可达500 mM，该浓度为 比在身体其他部位观察到的高出至少50倍。因此，对于 这些尿路病原体，尿素是一种信号分子，而尿素是一种信号 受体，提醒生物体它在尿路中。对……有义务 尿素是一种转录激活剂，对DNA有很高的亲和力。 未与尿素结合的尿素是不活跃的，对I)NA亲和力低 结合部位。这项建议中的研究是为了研究尿素-尿素的相互作用。 并确定与尿素结合相关的构象变化 导致活跃的尿毒症。提出了两种模型，一种是UrcR形成一个 二聚体，另一种是尿素作为单体活跃。建议进行研究 来证明这些模型中的一个。中研究了关键的urca-urer相互作用。 目标1，以及目标2中的尿素-尿素-DNA相互作用。目标3是确定 尿素、尿素结合的尿素以及尿素与DNA结合的尿素的X射线结构 结合部位。还将产生突变形式的尿素酶的结构。这 这项工作将阐明这一重要调控因子的分子机制。 尿毒力，以及扩展我们对AraC的认识-模糊的 转录激活剂。

DESCRIPTION(provided by applicant: Urease, which catalyzes the hydrolysis of urea to ammonia and carbonic acid is produced by diverse bacterial species including various aerobes, facultative anaerobes and obligate anaerohes Both Gram-negative and Gram-positive organisms are urease producers, as are species of mycobacteria and ureaplasma. Urease plays a significant role in virulence when expressed by urinary tract, oral, and gastroduodenal pathogens. Providencia stuartii and Proteus inirabilis, the two most common ureolytic uropathogens, express urcase only in the presence of urea. This urea-dependent expression is mediated by UreR, a transcriptional activator belonging to the AraCfamily of regulators. Evidence suggests that urea interacts directly with UreR, and thus is the effector molecule for this activator. Urea is Found at concentrations up to 500 mM in the urinary tract, a concentration that is at least 50 fold higher than that observed at other sites in the body. Thus for these uropathogens, urea is a signal molecule, and UreR is acting as a signal receptor, alerting the organism that it is in the urinary tract. UreR bound to urea is active as an transcriptional activator and has a high affinity for DNA. UreR not bound to urea is not active and has a low affinity for the I)NA binding site. Studies in this proposal are to examine the urea-UreR interaction and to determine the conformational changes associated with urea binding that result in active UreR. Two models are proposed, one in which UrcR forms a dimer, and the other in which UreR is active as a monomer. Studies are proposed to prove one of these models. The crucial urca-UreR interaction is examined in Aim #1, and the urea-UreR-DNA interaction in Aim #2. Aim #3 is to determine the X-ray structure of UreR, UreR bound to urea, and UreR bound to urea and the DNA binding site. Structures of mutant forms of UreR will also be generated. This work will elucidate the molecular mechanisms of this important regulator of a urovirulence, as well as extend our knowledge on the AraC-fainily of transcriptional activators.