Vijgenboom Erik, Busch Julie E, Canters Gerard W
Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands.
Microbiology (Reading). 1997 Sep;143 ( Pt 9):2853-2863. doi: 10.1099/00221287-143-9-2853.
The role of the blue copper protein azurin and cytochrome C551 as the possible electron donors to nitrite reductase in the dissimilatory nitrate reduction pathway in Pseudomonas aeruginosa have been investigated. It was shown by an in vivo approach with mutant strains of P. aeruginosa deficient in one or both of these electron-transfer proteins that cytochrome C551, but not azurin, is functional in this pathway. Expression studies demonstrated the presence of azurin in both aerobic and anaerobic cultures. A sharp increase in azurin expression was observed when cultures were shifted from exponential to stationary phase. The stationary-phase sigma factor, sigma s, was shown to be responsible for this induction. In addition, one of the two promoters transcribing the azu gene was regulated by the anaerobic transcriptional regulator ANR. An azurin-deficient mutant was more sensitive to hydrogen peroxide and paraquat than the wild-type P. aeruginosa. These results suggest a physiological role of azurin in stress situations like those encountered in the transition to the stationary phase.
在铜绿假单胞菌异化硝酸盐还原途径中，蓝色铜蛋白天青蛋白和细胞色素C551作为亚硝酸盐还原酶可能的电子供体的作用已被研究。通过对缺乏这两种电子传递蛋白中的一种或两种的铜绿假单胞菌突变株进行体内研究表明，细胞色素C551而非天青蛋白在该途径中起作用。表达研究表明，在需氧和厌氧培养物中均存在天青蛋白。当培养物从指数生长期转变为稳定期时，观察到天青蛋白表达急剧增加。已证明稳定期σ因子σs负责这种诱导。此外，转录azu基因的两个启动子之一受厌氧转录调节因子ANR调控。与野生型铜绿假单胞菌相比，天青蛋白缺陷型突变体对过氧化氢和百草枯更敏感。这些结果表明天青蛋白在向稳定期转变等应激情况下具有生理作用。
