Regulation of expression of terminal oxidases in Paracoccus denitrificans

Abstract

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 bc 1 -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 ba 3 -type quinol oxidase, while it positively regulated the activity of the cco promoter, which controls expression of the cbb 3 -type cytochrome c oxidase. The ctaDII and ctaC promoters, which control the expression of the aa 3 -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 wildtype. 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.

Cytochrome cbb 3 of Thioalkalivibrio is a Na + -pumping cytochrome oxidase

“…Exogenously expressed T. versutus cbb 3 Cox in strain AO1 reached a level comparable to that in T. versutus AL2 strain, as monitored using Western blotting. Expression of self-cbb 3 Cox in P. denitrificans WT strain grown aerobically (this study) reached the same high level as in semiaerobically grown cells (44), as quantified by real-time quantitative PCR. Each self-Cox level, aa 3 and cbb 3 , reached 70 pmol Cox/mg of membrane protein as determined by COreduced minus reduced spectra using extinction coefficients of 7 mM −1 ·cm −1 Fig.…”

The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry

“…Both genetic and biochemical studies have provided evidence that the cytochrome bo 3 quinol-oxidase has a cellular role that is distinct from that of the cytochrome bc 1 -dependent oxidases. 29,30 The bc 1 -complex, cytochrome c and the aa 3 -and cbb 3 -type oxidases are always present when O 2 is available to support respiration. By contrast, synthesis of the cytochrome bo 3 UQH 2 -oxidase requires the presence of not only O 2 , but also more highly reduced molecules as organic substrates for the catabolic processes that feed electrons into the UQ-pool.…”

“…31 However, the presence of cytochrome bo 3 is much lower during aerobic growth on malate (or succinate), for which full oxidation can supply only twelve (or fourteen) electrons and assimilation to the mean biomass composition consumes electrons. [29][30][31] We have found that the electron donating capacities of the catabolic substrates impact directly on the UQ/UQH 2 ratio in the membrane, i.e., the redox-poise of the UQ-pool. For P. pantotrophus HPLC analysis of the UQ-pool shows it to be substantially more reduced during aerobic growth on butyrate than during aerobic growth on succinate.…”

Regulation of the aerobic respiratory chain in the facultatively aerobic and hyperthermophilic archaeon Pyrobaculum oguniense

“…In these studies, additional functions of terminal oxidases were observed in a few species of bacteria. For example, Paracoccus denitrificans has three terminal oxidases: cbb 3 -type cytochrome c oxidase (FixN type) is expressed at a low oxygen concentration, aa 3 -type cytochrome c oxidase (SoxM type) is expressed at atmospheric oxygen concentration, and the pathway to ba 3 -type quinol oxidase (SoxM type) becomes active when the reduction state of the Q-pool increases (Otten et al, 1999(Otten et al, , 2001). E. coli has a bo 3 -type quinol oxidase (SoxM-type) that is utilized for atmospheric oxygen concentrations and a bd-type quinol oxidase (alternative oxidase) that is utilized for limited oxygen tension (Kita et al, 1984a, b).…”