Virulence factors of periodontopathogens

描述（由申请人提供）：革兰氏阴性厌氧菌是牙周病的主要病原体。此外，它们已被证明与其他健康并发症有关，如心血管疾病，糖尿病和早产低出生体重婴儿。牙龈卟啉单胞菌和Prev.中间型缺乏合成氯化血红素的能力，必须从环境中获取营养。尽管氯化血红素收购牙周病原体的重要性，主要的知识差距存在关于营养素的吸收和调节机制。在牙龈卟啉单胞菌W83的基因组上已经鉴定出几个编码氯化血红素转运蛋白的基因座;然而，这些基因座对该生物体中氯化血红素摄取的贡献仍然未知。此外，基因座编码的蛋白质的作用还没有很好地定义。我们已经确定了牙龈卟啉单胞菌生长所需的操纵子hmuYRSTUV，其中血红蛋白-触珠蛋白复合物作为氯高铁血红素来源。操纵子的同源物也存在于其他革兰氏阴性厌氧菌的基因组中，包括Prev。中间体17.我们的初步数据表明，hmu操纵子是铁调节。虽然铁吸收调节剂，毛皮，被证明可以调节在各种细菌中的氯化血红素摄取位点的表达，我们的初步研究表明，过氧化物反应调节剂，OxyR，在调节hmu位点的表达中起作用。因此，首先，我们将描述OxyR介导的调节机制。其次，我们将进一步确定hmu基因座在牙龈卟啉单胞菌中氯化血红素摄取中的作用。我们将从比较hmu基因座与存在于牙龈卟啉单胞菌W83基因组上的其他两个氯化血红素摄取基因座iht和tlr在该生物体中氯化血红素摄取中的作用开始我们的表征。接下来，我们将测试的假设，hmu操纵子是一个重要的氯化血红素收购机制，在牙周病原体和编码蛋白质提取氯化血红素分子从主机hemoproteins和运输氯化血红素跨两个膜（进入细胞质）。因此，我们将确定hmu编码的蛋白质的细胞定位，检查蛋白质彼此相互作用和与其它蛋白质相互作用的能力，并确定由基因座编码的蛋白质对牙龈卟啉单胞菌W83中氯化血红素摄取的贡献。最后，为了拓宽我们对氯化血红素在牙龈卟啉单胞菌毒力中的作用的理解，我们将研究氯化血红素和血红素蛋白在这种细菌中对基因表达的作用。

DESCRIPTION (provided by applicant): Gram negative anaerobic bacteria are the major etiological agents of periodontal diseases. In addition, they have been shown to be associated with other health complications such as cardiovascular diseases, diabetes, and preterm low birth weight babies. Both P. gingivalis and Prev. intermedia lack the capacity to synthesize hemin and must acquire the nutrient from the environment. Despite the importance of hemin acquisition in the periodontopathogens, major gaps in knowledge exist regarding the mechanisms of uptake and regulation of the nutrient. Several loci encoding hemin transport proteins have been identified on the genome of P. gingivalis W83; however, the contribution of these loci to hemin uptake in this organism remains unknown. Also, the role of the proteins encoded by the loci is not well defined. We have identified an operon, hmuYRSTUV, required for growth of P. gingivalis with hemoglobin-haptoglobin complexes as a hemin source. A homolog of the operon is also present on the genome of other Gram-negative anaerobic bacteria including Prev. intermedia 17. Our preliminary data indicate that the hmu operon is iron regulated. Although the ferric uptake regulator, Fur, was demonstrated to regulate the expression of hemin uptake loci in variety of bacteria, our preliminary studies show the peroxide responsive regulator, OxyR, plays a role in regulation of expression of the hmu locus. Thus, first we will characterize the OxyR-mediated mechanism of regulation. Second, we will further define the role of the hmu locus in hemin uptake in P. gingivalis. We will start our characterization from comparison of the role of the hmu locus with the other two hemin uptake loci, iht and tlr, present on the genome of P. gingivalis W83 in hemin uptake in this organism. Next, we will test the hypothesis that the hmu operon is an important hemin acquisition mechanism in both periodontopathogens and encodes proteins necessary to extract the hemin molecule from host hemoproteins and transport the hemin across both membranes (into the cytoplasm). Thus we will determine the cellular location of the hmu - encoded proteins, examine the ability of the proteins to interact with each other and with other proteins, and define the contribution of proteins encoded by the locus to hemin uptake in P. gingivalis W83. Lastly, to broaden our understanding of the role of hemin in virulence of P. gingivalis, we will examine the role of hemin and hemoproteins on gene expression in this bacterium.