Coordinate synthesis of azurin I and copper nitrite reductase in Alcaligenes xylosoxidans during denitrification

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• 作者：Roger L. Harris ; Robert R. Eady ; S. Samar Hasnain and R. Gary Sawers
• 关键词：Azurin ; Electron transfer ; Denitrification ; Gene regulation ; Nitrite reductase
• 刊名：Archives of Microbiology
• 出版年：2006
• 出版时间：September, 2006
• 年：2006
• 卷：186
• 期：3
• 页码：241-249
• 全文大小：448 KB
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Life Sciences
  Microbiology
  Microbial Ecology
  Biochemistry
  Cell Biology
  Biotechnology
  Ecology
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-072X

文摘

The denitrifying bacterium Alcaligenes xylosoxidans synthesises two azurins (Az), which are termed Az I and Az 2. Both function as effective electron donors to copper nitrite reductase (NiR) in vitro. As a first step towards identifying the physiological relevance of these electron transfer proteins in the denitrification process, the gene (azuA) encoding Az I was characterised and its expression with respect to denitrification determined. We show that the azuA gene from A. xylosoxidans is monocistronic and its expression is increased when cells are grown under denitrifying conditions in the presence of nitrate or nitrite. The expression pattern of azuA was similar, though not identical, to that of the monocistronic nirK gene, which encodes copper NiR, and is in accord with both gene products being synthesised when the bacterium denitrifies. Recombinant Az I was exported to the periplasm of the heterologous host Escherichia coli, was synthesised at very high levels (80 mg purified protein per litre) and was fully loaded with copper. Electron donation from reduced recombinant Az to NiR was indistinguishable from the activity determined with the native protein. Taken together, these findings indicate that in A. xylosoxidans azuA expression is coordinated with denitrification and recombinant Az I is processed and matured in the periplasm of E. coli in the same way it is in A. xylosoxidans.