Bacterial Cytochromes: II. Functional Aspects

Horio, Takekazu; Kamen,

doi:10.1146/annurev.mi.24.100170.002151

Cited by 56 publications

(9 citation statements)

References 49 publications

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“…The enriched cells used for making this particular batch of particles showed an Aao/A86o ratio of 0.93, and it seems likely that cells with higher ratios will prove to contain even greater quantities of cytochrome c2. An increase in the concentration of this cytochrome in cells with a high content of reaction-center BChl is consistent with the generally accepted view that reduced cytochrome c2 is the primary electron donor for the reduction of oxidized reaction-center BChl (15). The reducedminus-oxidized difference spectrum obtained with dithionite and ferricyanide as reductant and oxidant, respectively, also discloses (Fig.…”

Section: Reaction-center Bchl and Cytochromes In Membrane Fragmentssupporting

confidence: 88%

Mutational and Physiological Enhancement of Photosynthetic Energy Conversion in Rhodopseudomonas capsulata

Lien

Pietro

Gest

1971

Proc. Natl. Acad. Sci. U.S.A.

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Photosynthetic growth of Rhodopseudomonas capsulata, a nonsulfur purple bacterium, is severely inhibited by inorganic arsenate when this anion is present equimolar to orthophosphate in the culture medium.Studies on an arsenate-resistant mutant indicate that its resistance can be explained by a significantly increased photophosphorylation capacity of the energy-converting machinery, which can compensate for the decrease in adenosine triphosphate regeneration rate caused by esterification of arsenate in place of phosphate. Repeated subculture of the mutant in the presence of arsenate, under certain conditions, yields cell populations that have strikingly elevated contents of membrane-bound reactioncenter bacteriochlorophyll, cytochromes, and photophosphorylation coupling factor. Membranes from such cells show unusually high photophosphorylation activity, and can be expected to provide a useful experimental material for more refined analysis of the mechanism of the energy-conversion process.Results of previous studies (1, 2) on photosynthetic bacteria are consistent with the idea that the relative concentrations of the intracellular adenylate nucleotides define an important signal system in the complex regulatory networks that control both biosynthesis and the integration of synthetic activities with energy conversion. It may be expected that the rate of regeneration and the adenylate nucleotide profile in growing cells will be strongly affected by the presence of inorganic arsenate (Asi), which substitutes for orthophosphate (Pi) in numerous biochemical reactions, thereby leading to the formation of unstable esters. Asi, when present equimolar to Pi in the medium, is indeed very inhibitory for photosynthetic growth of the nonsulfur purple bacterium, Rhodopseudomonas capsulata (2). Mutants resistant to Asi can be readily isolated, and a study of one such organism (strain Z-1) suggested that the Asi-resistance in this particular strain is due to a significantly enhanced activity of the photophosphorylation system (2). This increased activity presumably enables the cells to compensate for the decrease in ATP regeneration rate occasioned by the Asi versus Pi competition in the energyconversion process. In this communication, we summarize supporting evidence that shows that the energy-converting membranes of Rps. capsulata Z-1 contain elevated amounts of reaction center bacteriochlorophyll (BChl), photophosphorylation coupling factor, and cytochromes. These modifications are associated with, and presumably responsible for, a very high photophosphorylation capacity of the energyconverting membranes of this organism. For routine transfers, inoculated cultures were incubated at 34°C and illuminated with banks of Lumiline lamps (Sylvania) at a light intensity of about 900 footcandles (fc); other details were as described by Sojka and Gest (1). The arsenate-resistant mutant, Rps. capsulata Z-1 (2), was similarly cultivated in a medium of the same composition, but supplemented with 10 mM sodium arsenate (Asi/Pi in th...

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Section: Reaction-center Bchl and Cytochromes In Membrane Fragmentssupporting

confidence: 88%

Mutational and Physiological Enhancement of Photosynthetic Energy Conversion in Rhodopseudomonas capsulata

Lien

Pietro

Gest

1971

Proc. Natl. Acad. Sci. U.S.A.

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“…In the bacterial respiratory chains, as in that of mitochondria, reducing equivalents originating in NADH, succinate, or other electron donors pass over a cascade of carriers to oxygen. Various aspects of bacterial respiratory chains are covered in recent reviews (49,122,168,353,390), all of which stress features in which the respiratory chains of bacteria differ from each other and from those of mitochondria. The essential point is that bacterial respiratory chains are more flexible: They oxidize a wider range of substrates than mitochondria do, and in some cases at least can employ sulfate or nitrate as terminal electron acceptors in place of oxygen.…”

Section: Oxidative Phosphorylationmentioning

confidence: 99%

Conservation and transformation of energy by bacterial membranes.

Harold¹

1972

Bacteriological Reviews

433

174

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“…The nature of the cytochrome-independent NADH and D-k3,Ctate oxidase activity has not been investigated. a 9 2 8 a (b) When grown in the presence of 5-aminolaevulinic acid, the rates of respiration of NADH and D-lactate are lower in extracts from cells grown anaerobically than from those grown aerobically. This point has been independently observed many times (e.g.…”

Section: Properties Of Strain A201mentioning

confidence: 99%

Electron‐Transport Chains of Escherichia coli

Haddock

Schairer²

1973

European Journal of Biochemistry

110

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1. The properties of a 5-aminolaevulinic acid synthetase-deficient mutant of Escherichia coli Ki2Ymel grown aerobically or anaerobically in the presence or absence of 5-aminolaevulinic acid are described. I n the absence of 5-aminolaevulinic acid no detectable cytochromes are produced, respiration rates are lowered, and the concentration of menaquinone in the cell is increased. The absence of 5-aminolaevulinic acid from the growth medium has no apparent effect on the Mg2+. dependent ATPase activity or on the concentrations of ubiquinone and flavoprotein(s) in the cell.2. Two methods for the reconstitution of respiration by cells grown aerobically or anaerobically in the absence of 5-aminolaevulinic acid are described. With intact cells, reconstitution is achieved in 3 h at 37 "C and is dependent on the presence of 5-aminolaevulinic acid and a fermentable carbon source. With cell-free extracts, respiration can be reconstituted by the addition of haematin in 15-20 min a t 37 "C provided that ATP is also present.3. It is concluded that the reconstitution of respiration by both methods is achieved in the absence of protein synthesis, indicating that the apoproteins of cytochromes, involved in electron transport with oxygen as terminal electron acceptor, are synthesized and incorporated into the membrane in the absence of haem synthesis. 4.From an examination of the cytochromes produced during the reconstitution experiments, it is suggested that two membrane-bound electron transport systems using oxygen as terminal electron acceptor can co-exist in E . coli. The first involving cytochrome b,,, with cytochrome o as terminal oxidase is the system normally present under aerobic growth conditions, and the second is induced under conditions when the concentrations of NADH and ADP in the cell are likely to be high and involves cytochrome b668 with cytochrome a, as the terminal oxidase.Escherichia coli forms a variety of electron transport systems depending upon the conditions chosen for growth (for reviews see [l-31). Under conditions of vigorous aeration the membrane-bound carriers include ubiquinone and cytochromes b,,,, bSBB and o [4-61, whereas under conditions of anaerobic growth the major membrane-bound electron carriers are menaquinone and cytochromes b,,, bSSB and a2 together with low concentrations of cytochrome a, [6--81. Two soluble c-type cytochromes, c548 and are also produced under anaerobic growth conditions [S]; cytochrome ~5 5 0 is associated with formate-hydrogen lyase activity [9] and cytochrome c548 is only present in low concentrations and its role is unknown. Under conditions of poor aeration, Enzymes. Mga++-dependent ATPase (EC 3.6.1.3) ; hexokinase (EC 2.7.1.1); catalase (EC 1.11.1.6); 6-aminolaevulinate synthetaee (EC 6.3.-.-).Nomenclature. Nonemclature of E. wli genes is that of A. L. Taylor (1970) Bacterial. Rev. 34, 155-176. or in the late log-phase of growth, a complex mixture of all these membrane-bound electron carriers is observed [S] (and unpublished observations). Under anaerobic growt...

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Bacterial Cytochromes: II. Functional Aspects

Cited by 56 publications

References 49 publications

Mutational and Physiological Enhancement of Photosynthetic Energy Conversion in Rhodopseudomonas capsulata

Mutational and Physiological Enhancement of Photosynthetic Energy Conversion in Rhodopseudomonas capsulata

Conservation and transformation of energy by bacterial membranes.

Electron‐Transport Chains of Escherichia coli

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