The Relationship between Proton Translocation and Cell Yields in the Facultative Methylotroph Pseudomonas AMI and a Mutant Lacking Cytochrome c

1979 ◽  
Vol 7 (1) ◽  
pp. 179-181 ◽  
Author(s):  
C. W. KEEVIL ◽  
CHRISTOPHER ANTHONY
Keyword(s):  
Cytochrome C ◽  
Proton Translocation ◽  
Facultative Methylotroph ◽  
The Relationship

scholarly journals Effect of growth conditions on the involvement of cytochrome c in electron transport, proton translocation and ATP synthesis in the facultative methylotroph Pseudomonas AM1

1979 ◽  
Vol 182 (1) ◽  
pp. 71-79 ◽  
Author(s):  
C. William Keevil ◽  
Christopher Anthony
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Proton Translocation ◽  
Atp Synthesis ◽  
Growth Conditions ◽  
Wild Type ◽  
Limited Growth ◽  
Bacterial Membranes ◽  
Facultative Methylotroph ◽  
Carbon Excess

The stoicheiometry of proton translocation, the amounts of cytochromes firmly bound to membranes, and cell yields with respect to succinate and O2 have been measured in the facultative methylotroph Pseudomonas AM1 and in the mutant lacking cytochrome c (mutant PCT76) during carbon-limited growth and carbon-excess growth. →H+/O ratios during endogenous respiration of about 4 were measured in wild-type bacteria grown in carbon-excess conditions, and in the mutant in all growth conditions. During methanol- or succinate-limited growth of wild-type bacteria the →H+/O ratio increased to about 6. Cell yields with respect to succinate and O2 were higher in wild-type than in the mutant lacking cytochrome c by an amount suggesting loss in the mutant of 30% of the ATP-generating capacity of wild-type bacteria. During carbon-limited growth on methanol or succinate some cytochrome c was tightly bound to bacterial membranes, whereas none was tightly bound in bacteria grown in batch-culture or in NH4+-limited conditions. It is proposed that the role of cytochrome c in Pseudomonas AM1 depends on growth conditions and hence on the ‘needs’ of the bacteria. During growth in carbon-excess conditions it is only required for methanol oxidation, mediating between methanol dehydrogenase and cytochrome a/a3. In these conditions oxidation of NADH and succinate by way of cytochrome b and cytochrome a/a3 occurs without the mediation of cytochrome c. This is the only route for oxidation of NADH and succinate in the cytochrome c-deficient mutant in all growth conditions. During carbon-limited growth the cytochrome c becomes bound to the membrane in such a way that it can mediate between cytochromes b and a/a3, hence becoming involved in proton translocation and ATP synthesis during NADH and succinate oxidation. An alternative possibility is that in wild-type bacteria the cytochrome c is always involved in electron transport, but that its involvement in measurable proton translocation only occurs in carbon-limited conditions.

scholarly journals The interaction between methanol dehydrogenase and the autoreducible cytochromes c of the facultative methylotroph Pseudomonas AM1

1980 ◽  
Vol 190 (2) ◽  
pp. 481-484 ◽  
Author(s):  
D T O'Keeffe ◽  
C Anthony
Keyword(s):  
Cytochrome C ◽  
Methanol Dehydrogenase ◽  
High Ph ◽  
First Order ◽  
Facultative Methylotroph ◽  
Cytochromes C ◽  
Pure Methanol

Cytochromes cH and cL were autoreduced at high pH (pK greater than 10) and the autoreduced cytochromes reacted with CO. The autoreduction was first-order with respect to oxidized cytochrome c and was reversible by lowering the pH. Pure methanol dehydrogenase reduced cytochrome c (in the absence of methanol) by lowering the pK for autoreduction to less than 8.5. A mechanism is proposed for the autoreduction of cytochrome c and its involvement in the reaction with methanol dehydrogenase.

scholarly journals Cytochrome redox states and respiratory control in mouse and beef heart mitochondria at steady-state levels of hypoxia

2015 ◽  
Vol 119 (10) ◽  
pp. 1210-1218 ◽  
Author(s):  
David K. Harrison ◽  
Mario Fasching ◽  
Mona Fontana-Ayoub ◽  
Erich Gnaiger
Keyword(s):  
Oxygen Consumption ◽  
Steady State ◽  
Cytochrome C ◽  
Respiratory Control ◽  
Low Noise ◽  
Mouse Heart ◽  
Redox States ◽  
Steady State Levels ◽  
Cytochrome Oxidation ◽  
The Relationship

Mitochondrial control of cellular redox states is a fundamental component of cell signaling in the coordination of core energy metabolism and homeostasis during normoxia and hypoxia. We investigated the relationship between cytochrome redox states and mitochondrial oxygen consumption at steady-state levels of hypoxia in mitochondria isolated from beef and mouse heart (BHImt, MHImt), comparing two species with different cardiac dynamics and local oxygen demands. A low-noise, rapid spectrophotometric system using visible light for the measurement of cytochrome redox states was combined with high-resolution respirometry. Monophasic hyperbolic relationships were observed between oxygen consumption, JO2, and oxygen partial pressure, Po2, within the range <1.1 kPa (8.3 mmHg; 13 μM). P50 j (Po2 at 0.5· Jmax) was 0.015 ± 0.0004 and 0.021 ± 0.003 kPa (0.11 and 0.16 mmHg) for BHImt and MHImt, respectively. Maximum oxygen consumption, Jmax, was measured at saturating ADP levels (OXPHOS capacity) with Complex I-linked substrate supply. Redox states of cytochromes aa3 and c were biphasic hyperbolic functions of Po2. The relationship between cytochrome oxidation state and oxygen consumption revealed a separation of distinct phases from mild to severe and deep hypoxia. When cytochrome c oxidation increased from fully reduced to 45% oxidized at 0.1 Jmax, Po2 was as low as 0.002 kPa (0.02 μM), and trace amounts of oxygen are sufficient to partially oxidize the cytochromes. At higher Po2 under severe hypoxia, respiration increases steeply, whereas redox changes are small. Under mild hypoxia, the steep slope of oxidation of cytochrome c when flux remains more stable represents a cushioning mechanism that helps to maintain respiration high at the onset of hypoxia.

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