Molecular mechanism of acquisition and storage of iron from oral environment by the periodontopathogen Porphyromonas gingivalis.

牙龈卟啉单胞菌是一种口腔厌氧革兰氏阴性菌，是成人牙周病的重要病原菌。牙龈假单胞菌的胞外和细胞相关蛋白主要由精氨酸特异性蛋白水解酶(RGP)和赖氨酸特异性蛋白水解酶(KGP)组成。我们发现牙龈假单胞菌的血红蛋白受体蛋白(HBR)是由rgpA、Kgp和hagA基因编码的HGP15结构域。我们已经用这些基因的组合构建了一些突变菌株。Kgp突变体在血液琼脂平板上生长时表现出较少的色素。发现rgpA rgpB双(Rgp-空)突变体没有菌毛，这与Rgp直接参与FimA-菌毛和表面75 kDa蛋白成熟的结果一致。RgpA rgpB kgp三倍体(rgp kgp-空)突变体不能在含有牛血清白蛋白的最低限度的…培养基中生长更多的是唯一的碳/能源来源，这表明这些蛋白酶对于降解环境蛋白质以产生可利用的多肽特别重要。此外，该三重突变体没有表现出对血红蛋白的吸附和血凝作用，这表明HGP15区编码的HBR蛋白和HGP44、HGP17和HGP27区编码的血凝素分别与这两个特性有关。我们还发现乳铁蛋白可以与HBR蛋白结合。乳铁蛋白与HBr的相互作用导致HBr从牙龈假单胞菌的细胞表面释放出来。牙龈假单胞菌不能利用乳铁蛋白作为铁源生长，相反，乳铁蛋白在以血红蛋白为唯一铁源的富含培养基中抑制细菌的生长。这些结果表明，乳铁蛋白通过与HBr结合，将其从细胞表面移除，从而扰乱血红蛋白的铁摄取系统，从而对牙龈假单胞菌具有抑菌作用。较少

Porphyromonas gingivalis is an oral anaerobic Gram-negative microorganism which is implicated as an important etiological agent of adult periodontal disease.P.gingivalis is asaccharolytic and highly proteolytic. Major extracellular and cell-associated proteinases of P.gingivalis are now found to consist of arginine-specific proteinase (Rgp) and lysine-specific proteinase (Kgp). We found that the hemoglobin receptor protein (HbR) of P.gingivalis was intragenically encoded as HGP15 domain region by rgpA, kgp and hagA genes. We have constructed a number of mutant strains with combination of these genes. The kgp mutant showed less-pigmented when grown on the blood agar plate. The rgpA rgpB double (Rgp-null) mutant was found to be unfimbriated, which is consistent with the result that Rgp was directly involved in maturation of the fimA-fimbriae and the surface 75 kDa protein. The rgpA rgpB kgp triple (Rgp Kgp-null) mutant could not grow in a minimal medium containing bovine serum albumin as … More the sole carbon/energy source, indicating that these proteinases are particularly important for degradation of environmental proteins to produce utilizable peptides. In addition, this triple mutant showed no hemoglobin adsorption or hemagglutination, indicating that the HbR protein encoded by HGP15 region and hemagglutinins encoded by HGP44, HGP17 and HGP27 regions are responsible for these two properties, respectively. We also found that lactoferrin could bind to the HbR protein. The interaction of lactoferrin with HbR led to the release of HbR from the cell surface of P.gingivalis. P.gingivalis could not utilize lactoferrin for its growth as an iron source and, in contrast, lactoferrin inhibited the growth of the bacterium in a rich medium containing hemoglobin as the sole iron source. These results suggest that lactoferrin has a bacteriostatic action on P.gingivalis by binding HbR, removing it from the cell surface, and consequently disrupting the iron uptake system from hemoglobin. Less