Otten M F, Stork D M, Reijnders W N, Westerhoff H V, Van Spanning R J
Department of Molecular Cell Physiology, Faculty of Biology, BioCentrum Amsterdam, Free University, The Netherlands.
Eur J Biochem. 2001 Apr;268(8):2486-97. doi: 10.1046/j.1432-1327.2001.02131.x.
In order to study the induction of terminal oxidases in Paracoccus denitrificans, their promoters were fused to the lacZ reporter gene and analysed in the wild-type strain, in an FnrP-negative mutant, in a cytochrome bc1-negative mutant, and in six single or double oxidase-negative mutant strains. The strains were grown under aerobic, semi-aerobic, and denitrifying conditions. The oxygen-sensing transcriptional-regulatory protein FnrP negatively regulated the activity of the qox promoter, which controls expression of the ba3-type quinol oxidase, while it positively regulated the activity of the cco promoter, which controls expression of the cbb3-type cytochrome c oxidase. The ctaDII and ctaC promoters, which control the expression of the aa3-type cytochrome c oxidase subunits I and II, respectively, were not regulated by FnrP. The activities of the latter two promoters, however, did decrease with decreasing oxygen concentrations in the growth medium, suggesting that an additional oxygen-sensing mechanism exists that regulates transcription of ctaDII and ctaC. Apparently, the intracellular oxygen concentration (as sensed by FnrP) was not the only signal to which the oxidase promoters responded. At given extracellular oxygen status, both the qox and the cco promoters responded to mutations in terminal oxidase genes, whereas the ctaDII and ctaC promoters did not. The change of electron distribution through the respiratory network, resulting from elimination of one or more oxidase genes, may have changed intracellular signals that affect the activities of the qox and cco promoters. On the other hand, the re-routing of electron distribution in the respiratory mutants hardly affected the oxygen consumption rate as compared to that of the wild-type. This suggests that the mutants adapted their respiratory network in such a way that they were able to consume oxygen at a rate similar to that of the wild-type strain.
为了研究反硝化副球菌中末端氧化酶的诱导情况，将它们的启动子与lacZ报告基因融合，并在野生型菌株、FnrP阴性突变体、细胞色素bc1阴性突变体以及六个单氧化酶或双氧化酶阴性突变体菌株中进行分析。这些菌株在需氧、半需氧和反硝化条件下生长。氧感应转录调节蛋白FnrP负调控qox启动子的活性，该启动子控制ba3型喹啉氧化酶的表达，而它正调控cco启动子的活性，该启动子控制cbb3型细胞色素c氧化酶的表达。分别控制aa3型细胞色素c氧化酶亚基I和II表达的ctaDII和ctaC启动子不受FnrP调控。然而，后两个启动子的活性确实随着生长培养基中氧浓度的降低而降低，这表明存在一种额外的氧感应机制来调节ctaDII和ctaC的转录。显然，细胞内氧浓度（由FnrP感知）不是氧化酶启动子响应的唯一信号。在给定的细胞外氧状态下，qox和cco启动子都对末端氧化酶基因的突变有反应，而ctaDII和ctaC启动子则没有。由于一个或多个氧化酶基因的缺失导致通过呼吸网络的电子分布变化，可能改变了影响qox和cco启动子活性的细胞内信号。另一方面，与野生型相比，呼吸突变体中电子分布的重新路由几乎不影响氧消耗率。这表明突变体以这样一种方式调整了它们的呼吸网络，使得它们能够以与野生型菌株相似的速率消耗氧气。
