Environmental Adaptation and Membrane Physiology of an Oral Pathogen

描述（由申请人提供）：放线菌群是一种革兰氏阴性兼性厌氧细菌，定植于人类口腔和上呼吸道。这种细菌与局部侵袭性牙周炎（LAP）密切相关。该菌是一种机会致病菌，可引起严重的全身性疾病，包括肺炎、感染性心内膜炎，并可能导致心血管疾病。该生物的致病性归因于包括粘附素、侵入素和毒素分泌在内的毒力决定因素。这些因子必须转移到两个不同的膜上才能发挥功能活性。在A.放线菌comitans中，生物起源和内外膜的蛋白质组成在很大程度上仍不清楚。我们已经发现了一个新的基因morC，编码一个141 kDa的膜蛋白，具有以前未知的功能。零突变体表现出外膜形态、膜通透性和白毒素分泌明显减少的变化。这些发现支持了MorC对维持膜形态和功能的重要性。形态发生蛋白（MorC）在革兰氏阴性人类病原体中高度保守。在Aggregatibacter及其相关属中，该基因位于一个受环境变化响应启动子控制的三基因操纵子中。该操纵子可能受双组分信号转导系统的调控。该基因和操纵子结构在多种细菌物种中的保守性表明该蛋白在这些微生物的生物学中起着重要作用。为了更好地了解MorC在膜生物发生和致病性中的作用，我们提出以下目标：1)MorC操纵子的分子表征；2)测定MorC的功能域；3)测定MorC在白毒素分泌和膜生物发生中的作用。完成上述目标所获得的信息可用于开发直接针对MorC蛋白的治疗方法或与现有治疗方法协同，以降低放线菌和其他病原体的致病潜力。

DESCRIPTION (provided by applicant): Aggregatibacter (Actinobacillus) actinomycetemcomitans is a gram-negative, facultative anaerobic bacterium that colonizes the human oral cavity and the upper respiratory tract. This bacterium is strongly associated with localized aggressive periodontitis (LAP). The organism is an opportunistic pathogen causing serious systemic diseases including pneumonia, infective endocarditis, and may contribute to cardiovascular disease. The pathogenicity of the organism has been ascribed to virulence determinants including adhesins, invasins and toxin secretion. These factors must translocate two distinct membranes to be functionally active. In A. actinomycetemcomitans, the biogenesis and protein composition of the inner and outer membranes remain largely undefined. We have identified a novel gene morC, encoding a 141 kDa membrane protein with previously unknown function. The null mutant showed changes in the morphology of the outer membrane, membrane permeability and a marked decreased secretion of leukotoxin. The importance of MorC to maintain membrane morphology and function is supported by these findings. The morphogenesis protein (MorC) is highly conserved among gram-negative human pathogens. In Aggregatibacter and related genera, the gene is located in a three-gene operon under the control of a promoter responsive to environmental changes. This operon may be regulated by a two-component signal transduction system. The conservation of this gene and the operon structure among a variety of bacterial species implies an important role of this protein in the biology of these microorganisms. To better understand the role of MorC in membrane biogenesis and pathogenicity, we propose the following aims: 1) molecular characterization of the morC operon; 2) determination of the functional domain(s) of MorC; and 3) determination of the role of MorC in leukotoxin secretion and membrane biogenesis. The information obtained from the accomplishment of the stated aims can be applied to the development of therapeutics directly targeted to the MorC protein or synergistically with existing therapies t reduce the pathogenic potential of A. actinomycetemcomitans and other pathogens.