scholarly journals Stimulations of Oxygen Uptake by Electron Transfer Inhibitors

1966 ◽  
Vol 41 (5) ◽  
pp. 797-802 ◽  
Author(s):  
S. Herman Lips ◽  
Jacob B. Biale
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake

scholarly journals Cultivation at high osmotic pressure confers ubiquinone 8–independent protection of respiration on Escherichia coli

2019 ◽  
Vol 295 (4) ◽  
pp. 981-993 ◽  
Author(s):  
Laura Tempelhagen ◽  
Anita Ayer ◽  
Doreen E. Culham ◽  
Roland Stocker ◽  
Janet M. Wood
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Escherichia Coli ◽  
Electron Transfer ◽  
Oxygen Uptake ◽  
Osmotic Pressure ◽  
Respiratory Chain ◽  
Membrane Lipid ◽  
E Coli ◽  
Uptake Rates

Ubiquinone 8 (coenzyme Q8 or Q8) mediates electron transfer within the aerobic respiratory chain, mitigates oxidative stress, and contributes to gene expression in Escherichia coli. In addition, Q8 was proposed to confer bacterial osmotolerance by accumulating during growth at high osmotic pressure and altering membrane stability. The osmolyte trehalose and membrane lipid cardiolipin accumulate in E. coli cells cultivated at high osmotic pressure. Here, Q8 deficiency impaired E. coli growth at low osmotic pressure and rendered growth osmotically sensitive. The Q8 deficiency impeded cellular O2 uptake and also inhibited the activities of two proton symporters, the osmosensing transporter ProP and the lactose transporter LacY. Q8 supplementation decreased membrane fluidity in liposomes, but did not affect ProP activity in proteoliposomes, which is respiration-independent. Liposomes and proteoliposomes prepared with E. coli lipids were used for these experiments. Similar oxygen uptake rates were observed for bacteria cultivated at low and high osmotic pressures. In contrast, respiration was dramatically inhibited when bacteria grown at the same low osmotic pressure were shifted to high osmotic pressure. Thus, respiration was restored during prolonged growth of E. coli at high osmotic pressure. Of note, bacteria cultivated at low and high osmotic pressures had similar Q8 concentrations. The protection of respiration was neither diminished by cardiolipin deficiency nor conferred by trehalose overproduction during growth at low osmotic pressure, but rather might be achieved by Q8-independent respiratory chain remodeling. We conclude that osmotolerance is conferred through Q8-independent protection of respiration, not by altering physical properties of the membrane.

scholarly journals Aspartate 205 in the Catalytic Domain of Naphthalene Dioxygenase Is Essential for Activity

1999 ◽  
Vol 181 (6) ◽  
pp. 1831-1837 ◽  
Author(s):  
Rebecca E. Parales ◽  
Juanito V. Parales ◽  
David T. Gibson
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake ◽  
Catalytic Domain ◽  
Mutant Protein ◽  
Wild Type ◽  
Naphthalene Dioxygenase ◽  
Major Pathway ◽  
Α Subunit ◽  
Mutant Proteins ◽  
Mononuclear Iron

ABSTRACT The naphthalene dioxygenase enzyme system carries out the first step in the aerobic degradation of naphthalene byPseudomonas sp. strain NCIB 9816-4. The crystal structure of naphthalene dioxygenase (B. Kauppi, K. Lee, E. Carredano, R. E. Parales, D. T. Gibson, H. Eklund, and S. Ramaswamy, Structure 6:571–586, 1998) indicates that aspartate 205 may provide the most direct route of electron transfer between the Rieske [2Fe-2S] center of one α subunit and mononuclear iron in the adjacent α subunit. In this study, we constructed four site-directed mutations that changed aspartate 205 to alanine, glutamate, asparagine, or glutamine to test whether this residue is essential for naphthalene dioxygenase activity. The mutant proteins were very inefficient in oxidizing naphthalene tocis-naphthalene dihydrodiol, and oxygen uptake in the presence of naphthalene was below detectable levels. The purified mutant protein with glutamine in place of aspartate 205 had identical spectral properties to wild-type naphthalene dioxygenase and was reduced by NADH in the presence of catalytic amounts of ferredoxinNAP and reductaseNAP. Benzene, an effective uncoupler of oxygen consumption in purified naphthalene dioxygenase, did not elicit oxygen uptake by the mutant protein. These results indicate that electron transfer from NADH to the Rieske center in the mutant oxygenase is intact, a finding consistent with the proposal that aspartate 205 is a necessary residue in the major pathway of electron transfer to mononuclear iron at the active site.

STIMULATORY EFFECT OF DL-3-HYDROXYBUTYRATE ON OXYGEN UPTAKE OF PERFUSED OMASAL LEAF

1984 ◽  
Vol 64 (5) ◽  
pp. 273-275 ◽  
Author(s):  
B. EMMANUEL ◽  
F. J. LOZEMAN ◽  
L. P. MILLIGAN
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake ◽  
Key Words ◽  
Rumen Microorganisms ◽  
Rumen Epithelium ◽  
Perfusion Chamber ◽  
Microbial Suspension

Oxygen uptake by the perfused omasal leaf was measured in the presence of mixed rumen microbial suspension which was kept anaerobically in the lumen side of a perfusion chamber. The addition of DL-3-hydroxybutyrate at 2, 4 and 8 mM concentrations to the microbial suspension increased oxygen withdrawal by 4.4, 11.1 and 15.5%, respectively. It is proposed that electron transfer through the coupled D(−)-3-hydroxybutyrate-acetoacetate reaction from rumen microorganisms to rumen epithelium yield energy for the latter tissue. Key words: Omasal leaf, oxygen uptake, microbes, DL-3-hydroxybutyrate

Origin of the ATP Formed during the Light-Dependent Oxygen Uptake Catalyzed by Rhodospirillum rubrum Chromatophores

1975 ◽  
Vol 30 (1-2) ◽  
pp. 46-52 ◽  
Author(s):  
Secundino Del Valle-Tascón ◽  
Juan Ramírez
Keyword(s):  
Electron Transfer ◽  
Oxygen Uptake ◽  
Electron Donor ◽  
Rhodospirillum Rubrum ◽  
Donor Concentration ◽  
Cyclic Flow ◽  
Atp Formation ◽  
Variable Extent ◽  
Transfer Inhibitor ◽  
Stimulation Of

Abstract The oxygen uptake which is observed when Rhodospirillum rubrum chromatophores are illuminated under air and in the presence of reduced 2,6-dichlorophenolindophenol (DCIP), 2,3,5,6-tetra-methyl-p-phenylenediamine (diaminodurene, DAD) or N,N′-tetramethyl-p-phenylenediamine (TMDP) depends on the electron-donor concentration according to the equation of Michaelis-Menten. The apparent Km for the donor is lowered by the electron-transfer inhibitor 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) which causes therefore a stimulation of the rate of the reaction at non-saturating concentrations of the donors. In contrast, the ATP formation which takes place simultaneously to oxygen uptake does not show an enzyme-like dependence on donor concentration. Moreover it is inhibited by HQNO to a variable extent, depending on the particular donor present and on its concentration. Therefore it appears that the HQNO-sensitive phosphorylation is coupled to a cyclic flow which coexists and competes with the non-cyclic flow from donor to oxygen. In the presence of HQNO, substrates and uncouplers of ATP formation accelerate somewhat the rate of the oxygen uptake supported by reduced DCIP and DAD. Thus part of the HQNO-resistant phosphorylation seems to be associated with the non-cyclic flow from those two donors to oxygen. The lack of stimulation by phosphorylation or by uncoupling of the TMPD-supported oxygen uptake does not permit a conclusion as to whether this reaction is coupled to ATP forma­ tion or not. Another part of the HQNO-resistant ATP formation is independent of the presence of oxygen and appears to be associated to cyclic flows which bypass the HQNO site. This type of phosphorylation is most important in the presence of TMPD.

A light optical diffractometer for electron microscopical images operating in line

1978 ◽  
Vol 36 (1) ◽  
pp. 86-87
Author(s):  
P. Bonhomme ◽  
A. Beorchia
Keyword(s):  
Electron Microscopy ◽  
Electron Transfer ◽  
Electron Microscope ◽  
Image Converter ◽  
Coherent Light ◽  
Spatial Filters ◽  
Electron Image ◽  
Electron Microscopical ◽  
Working Parameters ◽  
Amorphous Part

We have already described (1.2.3) a device using a pockel's effect light valve as a microscopical electron image converter. This converter can be read out with incoherent or coherent light. In the last case we can set in line with the converter an optical diffractometer. Now, electron microscopy developments have pointed out different advantages of diffractometry. Indeed diffractogram of an image of a thin amorphous part of a specimen gives information about electron transfer function and a single look at a diffractogram informs on focus, drift, residual astigmatism, and after standardizing, on periods resolved (4.5.6). These informations are obvious from diffractogram but are usualy obtained from a micrograph, so that a correction of electron microscope parameters cannot be realized before recording the micrograph. Diffractometer allows also processing of images by setting spatial filters in diffractogram plane (7) or by reconstruction of Fraunhofer image (8). Using Electrotitus read out with coherent light and fitted to a diffractometer; all these possibilities may be realized in pseudoreal time, so that working parameters may be optimally adjusted before recording a micrograph or before processing an image.

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