scholarly journals In vivo cycling of the Escherichia coli transcription factor FNR between active and inactive states

Microbiology ◽  
2005 ◽  
Vol 151 (12) ◽  
pp. 4063-4070 ◽  
Author(s):  
David P. Dibden ◽  
Jeffrey Green
Keyword(s):  
Escherichia Coli ◽  
De Novo ◽  
Oxygen Availability ◽  
Anaerobic Conditions ◽  
Aerobic Conditions ◽  
Fnr Protein ◽  
Transcription Regulators ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

FNR proteins are transcription regulators that sense changes in oxygen availability via assembly–disassembly of [4Fe–4S] clusters. The Escherichia coli FNR protein is present in bacteria grown under aerobic and anaerobic conditions. Under aerobic conditions, FNR is isolated as an inactive monomeric apoprotein, whereas under anaerobic conditions, FNR is present as an active dimeric holoprotein containing one [4Fe–4S] cluster per subunit. It has been suggested that the active and inactive forms of FNR are interconverted in vivo, or that iron–sulphur clusters are mostly incorporated into newly synthesized FNR. Here, experiments using a thermo-inducible fnr expression plasmid showed that a model FNR-dependent promoter is activated under anaerobic conditions by FNR that was synthesized under aerobic conditions. Immunoblots suggested that FNR was more prone to degradation under aerobic compared with anaerobic conditions, and that the ClpXP protease contributes to this degradation. Nevertheless, FNR was sufficiently long lived (half-life under aerobic conditions, ∼45 min) to allow cycling between active and inactive forms. Measuring the abundance of the FNR-activated dms transcript when chloramphenicol-treated cultures were switched between aerobic and anaerobic conditions showed that it increased when cultures were switched to anaerobic conditions, and decreased when aerobic conditions were restored. In contrast, measurement of the abundance of the FNR-repressed ndh transcript under the same conditions showed that it decreased upon switching to anaerobic conditions, and then increased when aerobic conditions were restored. The abundance of the FNR- and oxygen-independent tatE transcript was unaffected by changes in oxygen availability. Thus, the simplest explanation for the observations reported here is that the FNR protein can be switched between inactive and active forms in vivo in the absence of de novo protein synthesis.

scholarly journals Kinetic Analysis of the Oxidative Conversion of the [4Fe-4S]2+ Cluster of FNR to a [2Fe-2S]2+ Cluster

2004 ◽  
Vol 186 (23) ◽  
pp. 8018-8025 ◽  
Author(s):  
Victoria R. Sutton ◽  
Erin L. Mettert ◽  
Helmut Beinert ◽  
Patricia J. Kiley
Keyword(s):  
Oxidative Conversion ◽  
Anaerobic Conditions ◽  
Protein Levels ◽  
Detectable Difference ◽  
Fnr Protein ◽  
Sense And Respond ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

ABSTRACT The ability of FNR to sense and respond to cellular O2 levels depends on its [4Fe-4S]2+ cluster. In the presence of O2, the [4Fe-4S]2+ cluster is converted to a [2Fe-2S]2+ cluster, which inactivates FNR as a transcriptional regulator. In this study, we demonstrate that ∼2 Fe2+ ions are released from the reaction of O2 with the [4Fe-4S]2+ cluster. Fe2+ release was then used as an assay of reaction progress to investigate the rate of [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion in vitro. We also found that there was no detectable difference in the rate of O2-induced cluster conversion for FNR free in solution compared to its DNA-bound form. In addition, the rate of FNR inactivation was monitored in vivo by measuring the rate at which transcriptional regulation by FNR is lost upon the exposure of cells to O2; a comparison of the in vitro and in vivo rates of conversion suggests that O2-induced cluster conversion is sufficient to explain FNR inactivation in cells. FNR protein levels were also compared for cells grown under aerobic and anaerobic conditions.

The Leeuwenhoek Lecture, 1995. Adaptation to life without oxygen

1995 ◽  
Vol 350 (1332) ◽  
pp. 189-202 ◽  
Keyword(s):  
Escherichia Coli ◽  
Oxygen Availability ◽  
Regulatory Mechanisms ◽  
Anaerobic Conditions ◽  
The Earth ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

The Earth was populated by anaerobic organisms for at least a thousand million years before the atmosphere became oxygenated and aerobes could evolve. M any bacteria like Escherichia coli retain the ability to grow under both aerobic and anaerobic conditions. Recent studies have revealed some global regulatory mechanisms for activating or repressing the expression of relevant genes in response to oxygen availability. These mechanisms ensure that the appropriate metabolic mode is adopted when bacteria switch between aerobic and anaerobic environments.

PRODUCTION AND PROPERTIES OF 2,3-BUTANEDIOL: VII. FERMENTATION OF WHEAT BY AEROBACILLUS POLYMYXA UNDER AEROBIC AND ANAEROBIC CONDITIONS

1946 ◽  
Vol 24f (1) ◽  
pp. 1-11 ◽  
Author(s):  
G. A. Adams
Keyword(s):  
Carbon Dioxide ◽  
Anaerobic Fermentation ◽  
Anaerobic Conditions ◽  
Mechanical Agitation ◽  
Fermentation Time ◽  
Aerobic Conditions ◽  
Ethanol Formation ◽  
Time Required ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

Aeration by mechanical agitation of 15% wheat mash fermented by Aerobacillus polymyxa inhibited the formation of 2,3-butanediol and particularly of ethanol. Aeration of similar mashes by passage of finely dispersed air or oxygen at the rate of 333 ml. per minute per litre of mash increased the rate of formation and yield of 2,3-butanediol but inhibited ethanol formation. However, the over-all time required for the completion of fermentation was not shortened from the usual 72 to 96 hr. required for unaerated mashes. There was no evidence of a shift from fermentative to oxidative dissimilation. Under aerobic conditions, the final butanediol–ethanol ratio was approximately 3:1. Anaerobic conditions, as produced by the passage of nitrogen or hydrogen through the mash, increased the rate of formation of both butanediol and ethanol and shortened the fermentation time to about 48 hr. Under these conditions, the butanediol–ethanol ratio was reduced to about 1.3:1.0. Carbon dioxide gave a butanediol–ethanol ratio resembling that of anaerobic fermentation but did not reduce fermentation time.

Further evidence for the existence of cyclic and non-cyclic photophosphorylation in vivo by means of desaspidin and DCMU

1967 ◽  
Vol 22 (5) ◽  
pp. 537-540 ◽  
Author(s):  
W. Urbach ◽  
W. Simonis
Keyword(s):  
Antimycin A ◽  
Anaerobic Conditions ◽  
Intact Cells ◽  
Cyclic Photophosphorylation ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

The effect of desaspidin and DCMU on photophosphorylation in intact cells under aerobic and anaerobic conditions has been studied. Desaspidin is mainly effective in N2 and inhibits under these conditions the DCMU-insensitive cyclic photophosphorylation in vivo like antimycin A. The inhibition of the phosphorylation in light by DCMU is stronger in N2 than in air which suggests a partial existence of oxydative phosphorylation during illumination.

The energy metabolism of adult Haemonchus contortus, in vitro

Parasitology ◽  
1978 ◽  
Vol 77 (3) ◽  
pp. 255-271 ◽  
Author(s):  
P. F. V. Ward ◽  
N. S. Huskisson
Keyword(s):  
Energy Metabolism ◽  
Haemonchus Contortus ◽  
Aerobic Incubation ◽  
Anaerobic Conditions ◽  
Physically Active ◽  
Aerobic Conditions ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

SummaryA comparison was made of the major excretory products when adult Haemonchus contortus worms were incubated with D-[U-14C]glucose under aerobic and anaerobic conditions. Catabolites measured were propan-1-ol, acetate, n-propionate and CO2 and the only major difference was that nearly twice as much CO2 both in terms of quantity and radioactivity was excreted under aerobic than anaerobic conditions. The worms were also much more physically active under aerobic conditions. When worms were incubated under aerobic conditions with increasing amounts of fluoroacetate their CO2 production was progressively reduced to the anaerobic level. Their movement and their ability to clump together was also progressively reduced. After aerobic incubation with fluoroacetate and D-[U-14C]g1ucose the quantity and radioactivity of citrate within worms increased greatly. When worms were similarly incubated anaerobically no increase in citrate occurred, no radioactivity was associated with the citrate and the worms appeared physically unaffected. When worms were incubated aerobically with fluoro[1-14C]acetate they produced radioactive fluorocitrate.

Sign in / Sign up

Export Citation Format

Share Document