The oxygen affinity of cytochrome bo' in Escherichia coli determined by the deoxygenation of oxyleghemoglobin and oxymyoglobin: Km values for oxygen are in the submicromolar range

D'mello, Rita; Hill, Susan; Poole, Robert K.

doi:10.1128/jb.177.3.867-870.1995

Cited by 62 publications

(44 citation statements)

References 30 publications

(34 reference statements)

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“…The K m value of aa 3 could not be determined using myoglobin, because oxymyoglobin was immediately oxidized to metmyoglobin when the membrane fraction of QXAaS2 was added to the reaction mixture. The K m values determined by measurements using an oxygen electrode were significantly higher than those determined using myoglobin, likely because of the relatively low sensitivity and slow response of the electrode to change in oxygen concentration (41). Although the oxygen electrode data underestimated the actual affinity of the terminal oxidases for oxygen, the relative difference of the estimated K m values was similar to that of the spectrophotometric data.…”

Section: Growth Profile Of Multiple Terminal Oxidase Knockout Mutantssupporting

confidence: 56%

Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa

et al. 2014

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The ubiquitous opportunistic pathogen Pseudomonas aeruginosa has five aerobic terminal oxidases: bo 3 -type quinol oxidase (Cyo), cyanide-insensitive oxidase (CIO), aa 3 -type cytochrome c oxidase (aa 3 ), and two cbb 3 -type cytochrome c oxidases (cbb 3 -1 and cbb 3 -2). These terminal oxidases are differentially regulated under various growth conditions and are thought to contribute to the survival of this microorganism in a wide variety of environmental niches. Here, we constructed multiple mutant strains of P. aeruginosa that express only one aerobic terminal oxidase to investigate the enzymatic characteristics and in vivo function of each enzyme. The K m values of Cyo, CIO, and aa 3 for oxygen were similar and were 1 order of magnitude higher than those of cbb 3 -1 and cbb 3 -2, indicating that Cyo, CIO, and aa 3 are low-affinity enzymes and that cbb 3 -1 and cbb 3 -2 are high-affinity enzymes. Although cbb 3 -1 and cbb 3 -2 exhibited different expression patterns in response to oxygen concentration, they had similar K m values for oxygen. Both cbb 3 -1 and cbb 3 -2 utilized cytochrome c 4 as the main electron donor under normal growth conditions. The electron transport chains terminated by cbb 3 -1 and cbb 3 -2 generate a proton gradient across the cell membrane with similar efficiencies. The electron transport chain of aa 3 had the highest proton translocation efficiency, whereas that of CIO had the lowest efficiency. The enzymatic properties of the terminal oxidases reported here are partially in agreement with their regulatory patterns and may explain the environmental adaptability and versatility of P. aeruginosa.

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Section: Growth Profile Of Multiple Terminal Oxidase Knockout Mutantssupporting

confidence: 56%

Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa

et al. 2014

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“…Cytochrome bd-I has a high affinity for oxygen (K m ϭ 0.27 M (8)) and is induced under microoxic conditions, whereas the lower affinity (K m ϭ 6.05 M (8)) cytochrome boЈ is highly expressed under oxic conditions. The K m values for both oxidases are much lower when measured without recourse to oxygen electrodes (9,10), but the higher oxygen affinity of cytochrome bd-I is well established. Both oxidases are repressed under anoxic conditions as components of the Arc and Fnr regulons (11)(12)(13)(14).…”

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confidence: 99%

Compensations for Diminished Terminal Oxidase Activity in Escherichia coli

Shepherd

Sanguinetti

Cook

et al. 2010

Journal of Biological Chemistry

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Escherichia coli possesses cytochrome bo (CyoABCDE), cytochrome bd-I (CydAB), and cytochrome bd-II (AppBC) quinol oxidases, all of which can catalyze the terminal step in the aerobic respiratory chain, the reduction of oxygen by ubiquinol. Although CydAB has a role in the generation of ⌬pH, AppBC has been proposed to alleviate the accumulation of electrons in the quinone pool during respiratory stress via electroneutral ubiquinol oxidation. A cydB mutant strain exhibited lower respiration rates while maintaining a wild type growth rate. Transcriptomic analysis revealed a dramatic up-regulation of AppBC in the cydB strain, accompanied by the induction of genes involved in glutamate/␥-aminobutyric acid (GABA) antiport, the GABA shunt, the glyoxylate shunt, respiration (including appBC), motility, and osmotic stress. Transcription factor modeling suggests that the underpinning regulation is largely controlled by H-NS, GadX, FlhDC, and AppY. The transcriptional adaptations imply that cydB cells contribute to the proton motive force via consumption of intracellular protons and glutamate/GABA antiport. Indeed, supplementation of culture medium with L-glutamate stimulates growth in a cydB strain. Phenotype analyses of the cydB strain confirm decreased motility and elevated acid resistance and also an elevated cytochrome d spectroscopic signal in cells grown at low pH. We propose a mechanism via which E. coli can compensate for the loss of cytochrome bd-I activity; cytochrome bd-II-mediated quinol oxidation prevents the accumulation of NADH, whereas GABA synthesis/antiport maintains the proton motive force for ATP production.

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“…Cytochrome boЈ is a member of the heme-copper superfamily of terminal oxidases; it is a proton pump (42) and has a moderately high affinity for oxygen, with a K m in the submicromolar range (11). In contrast, cytochrome bd uses a heme-heme binuclear center to bind oxygen as a surprisingly stable oxygenated form and reduce oxygen to water (20,39).…”

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confidence: 99%

Nitric oxide, nitrite, and Fnr regulation of hmp (flavohemoglobin) gene expression in Escherichia coli K-12

et al. 1996

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Escherichia coli possesses a soluble flavohemoglobin, with an unknown function, encoded by the hmp gene. A monolysogen containing an hmp-lacZ operon fusion was constructed to determine how the hmp promoter is regulated in response to heme ligands (O 2 , NO) or the presence of anaerobically utilized electron acceptors (nitrate, nitrite). Expression of the ⌽(hmp-lacZ)1 fusion was similar during aerobic growth in minimal medium containing glucose, glycerol, maltose, or sorbitol as a carbon source. Mutations in cya (encoding adenylate cyclase) or changes in medium pH between 5 and 9 were without effect on aerobic expression. Levels of aerobic and anaerobic expression in glucose-containing minimal media were similar; both were unaffected by an arcA mutation. Anaerobic, but not aerobic, expression of ⌽(hmp-lacZ)1 was stimulated three-to four-fold by an fnr mutation; an apparent Fnr-binding site is present in the hmp promoter. Iron depletion of rich broth medium by the chelator 22-dipyridyl (0.1 mM) enhanced hmp expression 40-fold under anaerobic conditions, tentatively attributed to effects on Fnr. At a higher chelator concentration (0.4 mM), hmp expression was also stimulated aerobically. Anaerobic expression was stimulated 6-fold by the presence of nitrate and 25-fold by the presence of nitrite. Induction by nitrate or nitrite was unaffected by narL and/or narP mutations, demonstrating regulation of hmp by these ions via mechanisms alternative to those implicated in the regulation of other respiratory genes. Nitric oxide (10 to 20 M) stimulated aerobic ⌽(hmp-lacZ)1 activity by up to 19-fold; soxS and soxR mutations only slightly reduced the NO effect. We conclude that hmp expression is negatively regulated by Fnr under anaerobic conditions and that additional regulatory mechanisms are involved in the responses to oxygen, nitrogen compounds, and iron availability. Hmp is implicated in reactions with small nitrogen compounds.Escherichia coli is generally considered to consume oxygen by using two membrane-bound terminal oxidases for aerobic respiration, cytochromes boЈ and bd (15,36). Cytochrome boЈ is a member of the heme-copper superfamily of terminal oxidases; it is a proton pump (42) and has a moderately high affinity for oxygen, with a K m in the submicromolar range (11). In contrast, cytochrome bd uses a heme-heme binuclear center to bind oxygen as a surprisingly stable oxygenated form and reduce oxygen to water (20, 39). Cytochrome bd is believed not to be a proton pump but has an extraordinarily high apparent affinity for oxygen, with a K m in vivo as low as 5 nM (12). The distinct properties of these oxidases, and thus their suitability for growth under different aerobic conditions, requires that they be differentially regulated. Cytochromes boЈ and bd are maximally synthesized during growth with high (4) or limited (14) aeration, respectively. Expression of operons comprising the oxidase structural genes (cyoABCDE and cydAB, respectively) are each affected by Fnr and ArcA/ArcB, although dissection of the dire...

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The oxygen affinity of cytochrome bo' in Escherichia coli determined by the deoxygenation of oxyleghemoglobin and oxymyoglobin: Km values for oxygen are in the submicromolar range

Cited by 62 publications

References 30 publications

Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa

Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa

Compensations for Diminished Terminal Oxidase Activity in Escherichia coli

Nitric oxide, nitrite, and Fnr regulation of hmp (flavohemoglobin) gene expression in Escherichia coli K-12

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