Characterization of the single superoxide dismutase of Staphylococcus xylosus
Characterization of the single superoxide dismutase of Staphylococcus xylosus
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DOI：
10.1128/aem.67.9.4096-4104.2001
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发表时间：
2001-09-01
影响因子：
4.4
通讯作者：
Talon, R
中科院分区：
文献类型：
--
作者：
Barrière, C;Brückner, R;Talon, R
木糖葡萄球菌是一种兼性厌氧细菌，用作发酵肉制品的发酵剂。在试图分析这种生物体的抗氧化能力，超氧化物歧化酶（SOD）的特点。S.木糖含有单一的细胞质SOD，这是不受H2 O2抑制。SOD活性在粗提物中完全丧失后，金属耗尽，但它可以恢复锰和铁非常弱。因此建议S.木糖SOD是一种嗜锰酶。相应的基因sod是从S.木糖DNA和补充大肠杆菌SOD缺陷突变体的生长缺陷。从核苷酸序列推断，sod编码199个氨基酸的蛋白质，分子量为22.5 kDa。两个转录起始位点25和120 bp的sod起始密码子上游被确定。该基因下游的终止子样结构表明单顺反子sod mRNA。利用sod启动子与无启动子的β-半乳糖苷酶基因的融合研究了sod表达的调控。超氧化物歧化酶的表达不受锰和百草枯略有增加。它在复合培养基中的稳定期诱导，但在化学成分确定的培养基中不诱导。为了研究SOD的生理作用，构建了一个SOD活性缺失突变体。生长实验表明，在复合培养基中，sod不是好氧生长所必需的。然而，在没有亮氨酸，异亮氨酸和缬氨酸的化学成分确定的培养基中，与野生型菌株相比，sod突变体几乎不能生长。此外，该突变体对高压氧和百草枯敏感。因此，SOD在保护S.氧化应激的木糖。
Staphylococcus xylosus is a facultative anaerobic bacterium used as a starter culture for fermented meat products. In an attempt to analyze the antioxidant capacities of this organism, the superoxide dismutase (SOD) was characterized. S. xylosus contains a single cytoplasmic SOD, which was not inhibited by H2O2. The SOD activity in crude extracts was completely lost upon metal depletion, but it could be recovered by manganese and very weakly by iron. It is therefore suggested that the S. xylosus SOD is a manganese-preferring enzyme. The corresponding gene, sod, was isolated from a genomic library of S. xylosus DNA and complemented the growth defect of an Escherichia coli SOD-deficient mutant. As deduced from the nucleotide sequence, sod encodes a protein of 199 amino acids with a molecular mass of 22.5 kDa. Two transcriptional start sites 25 and 120 bp upstream of the sod start codon were identified. A terminator-like structure downstream of the gene suggested a monocistronic sod mRNA. Regulation of sod expression was studied using fusions of the sod promoters to a genomic promoterless beta -galactosidase gene. The sod expression was not affected by manganese and increased slightly with paraquat. It was induced during stationary phase in a complex medium but not in a chemically defined medium. To investigate the physiological role of SOD, a mutant devoid of SOD activity was constructed. Growth experiments showed that sod is not essential for aerobic growth in complex medium. However, in chemically defined medium without leucine, isoleucine, and valine, the sod mutant hardly grew, in contrast to the wild-type strain. In addition, the mutant was sensitive to hyperbaric oxygen and to paraquat. Therefore, sod plays an important role in the protection of S. xylosus from oxidative stress.