Superoxide dismutase-encoding gene of the obligate anaerobe Porphyromonas gingivalis is regulated by the redox-sensing transcription activator OxyR
Superoxide dismutase-encoding gene of the obligate anaerobe Porphyromonas gingivalis is regulated by the redox-sensing transcription activator OxyR
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DOI：
10.1099/mic.0.28537-0
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发表时间：
2006-04-01
期刊：
影响因子：
2.8
通讯作者：
Nakayama, K
中科院分区：
文献类型：
--
作者：
Ohara, N;Kikuchi, Y;Nakayama, K
口腔厌氧菌牙龈卟啉单胞菌的基因组DNA序列检测显示，该微生物具有过氧化物感应转录激活子OxyR，但不具有超氧化物感应转录因子SoxR。通过双向凝胶电泳对牙龈假单胞菌氧化应激反应蛋白的研究发现，两个蛋白在氧化条件下显著上调。在一个牙龈卟啉卟啉氧r突变体中，这两种蛋白在有氧条件下不被过氧化氢诱导。通过n端氨基酸测序，发现这两个蛋白分别为超氧化物歧化酶和烷基氢过氧化物还原酶，分别由sod和ahpC编码。Northern blot和lacZ融合分析显示，OxyR正调控牙龈假单胞菌的sod和ahpC。引物延伸分析定位了sod和ahpC的启动子区域，并在其推测的oxyr结合序列附近发现了-35盒这些启动子。此外，sod和ahpC的启动子区域具有结合牙龈假单胞菌OxyR蛋白的能力。这些结果表明，牙龈假单胞杆菌的sod是OxyR调控因子之一，这表明在牙龈假单胞杆菌中，OxyR的功能是细胞内氧化还原传感器而不是过氧化物传感器。脆弱拟杆菌（Bacteroides fragilis）与牙龈卟啉杆菌（P. gingivalis）在分类上有亲缘关系，其sod基因受氧化还原胁迫诱导，但不受其OxyR控制。含有脆性双歧杆菌sod启动子区的DNA片段可以结合牙龈双歧杆菌的OxyR蛋白；然而，DNA片段内的假设的OxyR结合序列与其启动子的推定-35盒距离为14个碱基。
Inspection of the genomic DNA sequence of the oral anaerobe Porphyromonas gingivalis reveals that the micro-organism possesses the peroxide-sensing transcription activator OxyR, but not the superoxide-sensing transcription factor SoxR. Investigatation of oxiclative-stress-responsive proteins in P. gingivalis by two-dimensional gel electrophoresis showed that two proteins were predominantly upregulated in oxidative conditions. In a P. gingivalis oxyR mutant these two proteins were not induced by treatment with hydrogen peroxide under aerobic conditions. By N-terminal amino acid sequencing, the two proteins were found to be superoxide dismutase and alkyl hydroperoxide reductase, encoded by sod and ahpC, respectively. Northern blot and lacZ fusion analyses revealed that P. gingivalis sod and ahpC were positively regulated by OxyR. Primer extension analysis located the promoter regions of sod and ahpC, and putative -35 boxes of these promoters were found immediately adjacent to their putative OxyR-binding sequences. Moreover, the promoter regions of sod and ahpC had the ability to bind P. gingivalis OxyR protein. These results demonstrate that P. gingivalis sod is one of the OxyR regulons, suggesting that OxyR functions as an intracellular redox sensor rather than a peroxide sensor in this organism. A sod gene of Bacteroides fragilis, which is taxonomically related to P. gingivalis, is inducible by redox stresses but not controlled by its OxyR. A DNA fragment including the B. fragilis sod promoter region could bind the P. gingivalis OxyR protein; however, a putative OxyR binding sequence within the DNA fragment was 14 bases distant from a putative -35 box of its promoter.