Multiplicity of Electron Transport Reactions in Bacterial Photosynthesis

Frenkel, Albert W.

doi:10.1111/j.1469-185x.1970.tb01177.x

Cited by 52 publications

(6 citation statements)

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“…Keister andMinto (1969) andR. Govindjee andSybesma (1972) showed that this reduction was driven by a light-induced, reverse electron transport which required ATP or an equivalent energy source (Vernon 1958, Chance and Hollunger 1961, Stanier 1961, Mitchell 1966, Frenkel 1970, Lascelles 1973, Gromet-Elhanan 1977, Gest 1982.…”

Section: (B ) Photophosphorylation Electron Transport and Developmenmentioning

confidence: 99%

Recollections

Frenkel

1993

Photosynth Res

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About 1939, Sam Ruben and Martin Kamen introduced me to the emergent application of artificial radio-isotopes in the study of photosynthesis. While my own experiments on CO2 fixation by isolated chloroplasts turned out to be negative, their laboratory provided me with an informative and exciting experience. Also, there were many stimulating contacts with Cornelis van Niel, Robert Emerson, Don DeVault and many other outstanding scientists. Efforts on my part to obtain a better understanding of intermediary metabolism, eventually led me to Fritz Lipmann's laboratory. There I was encouraged to study the metabolic activities of cell-free preparations of photosynthetic purple bacteria. Investigations of oxidative phosphorylation by isolated bacterial chromatophores in the dark raised questions about the possible effects of light on the phosphorylation activities of such preparations. Surprisingly, high rates of phosphorylation were observed in the light in the absence of molecular oxygen ('light-induced phosphorylation'). In this process, adenosine diphosphate (ADP) and inorganic phosphate (Pi) could be converted quantitatively into adenosine triphosphate (ATP). It was postulated that this process was 'cyclic' in nature, as only catalytic concentrations of added electron donors were required. Later, at Minnesota, it could be shown that similar chromatophore preparations, in the presence of suitable electron donors, could reduce nicotinamide-adenine dinucleotide (NAD(+)) to NADH in the light. It was then demonstrated that the chromatophores of Rhodospirilum rubrum, as well as the smaller membrane components derived from them, must contain the active metabolic components for these photosynthetic reactions.These observations, and studies on the kinetics of the formation and decay of light-induced free radicals, appeared to demonstrate the usefulness of bacterial chromatophores and of their membrane fragments in the study of partial reactions of bacterial photosynthesis. Since that time, numerous investigators elsewhere have carried out remarkable research on the purification and eventual crystallization of distinct bacterial membrane components, capable of carrying out well characterized photochemical and electron transport reactions.

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Section: (B ) Photophosphorylation Electron Transport and Developmenmentioning

confidence: 99%

Recollections

Frenkel

1993

Photosynth Res

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“…Die Bedeutung der Forschung an Reaktionszentren von photosynthetischen Prokaryoten wird deutlich durch die fast alljahrlich erscheinenden, ausfiihrlichen Obersichtsartikel: FRENKEL (1970), CLAYTON (1971CLAYTON ( und 1973, SAUER (1975), PARSON (1974) und PARSON und . Von den drei Familien phototropher Bakterien -Rhodospirillaceae, Chromatiaceae und Chlorobiaceae -sind vor allem Arten der Familie der Rhodospirillaceae seit Jahren intensiv bearbeitet worden.…”

Section: Introductionunclassified

“…, ) FRENKEL (1970, FRENKEL (1970) Pxasox und A-450 ist die Bezeichnung fiir eine Rbodospeudomonas spheroides-RC-Komponente, deren Absorptionsanderung bei 450 nm mit der Riickreduktionsrate von P S70 -I-iibereinstimmt (WRAIGHT et a1. 1975).…”

Section: Introductionunclassified

Zur Struktur von Reaktionszentren in phototrophen Bakterien: eine Standortbestimmung

Hanselmann

1977

Berichte der Deutschen Botanischen Gesellschaft

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“…In bacteria lacking the non-cyclic electron transport system, reduced pyridine nucleotides (required for biosynthetic purposes) are produced by reverse electron Row driven by ATP. The reader is referred to the article of Frenkel (1970) for an extensive discussion of the proposed electron transport reactions in bacterial photosynthesis.…”

Section: Introductionmentioning

confidence: 99%

“…Literature is cited on an elective rather than a comprehensive basis. For detailed accounts of other 1 1 1 1 1 1 1 aspects of bacterial photosynthesis, the reader is referred to recent reviews (Gest et ul., 1963;Govindjee, 1974;Parson and Cogdell, 1975;Frenkel, 1970;Walker and Crofts, 1970;Clayton, 1973;Vernon, 1968;Loach and Hales, 1976;.…”

Section: Introductionmentioning

confidence: 99%

A Survey of Epr Investigations of Bacterial Photosynthesis

Corker

1976

Photochem & Photobiology

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Abstract-Investigations in which EPR has been used as a probe of the mechanism of the primary quantum conversion reaction and/or electron transport reactions in bacterial photosynthesis are surveyed. These investigations include studies of whole cell organisms and simpler sub-cellular preparations, chromatophores and bacteriochlorophyll-protein complexes.Electron paramagnetic resonance studies have successfully demonstrated that the primary donor of the photosynthetic, photochemical reaction involves a dimer of bacteriochlorophyll, generally referred to as P870. P870 is photochemically oxidized to a cation radical which exhibits a g = 2.0025 EPR signal. Comparative studies of the time behaviour of this signal in whole cells and in sub-cellular preparations show that electron flow in the whole cells is substantially different than in the cell-free systems.The primary acceptor molecule of the photochemical reaction has not been conclusively identified. When it is photochemically reduced, it exhibits a broad EPR absorbance centered at g = 1.8 observable only at low temperatures. This signal involves an iron atom and a quinone molecule. Two possible identifications of the species responsible for the g = 1.8 signal are an iron-quinone complex and an iron-sulfur protein. The latter identification would require that one primary acceptor function for two primary donors and that the removal of a tightly held quinone alter the integrity of the system so as to inhibit the photochemistry.When the primary acceptor is chemically reduced, a photo-induced, polarized triplet EPR spectrum is detected. Both absorption and emission lines arq observed as if only one substate (m = 0) of the triplet manifold is populated. The zero field parameters of the triplet spectrum suggest that the triplet is formed through a decay of a biradical, not through an optical singlet to triplet transition.Low temperature EPR studies of photosynthetic preparations which had been poised at room temperature by subjecting the preparations to different redox potentials and/or dark adaptation and illumination show the presence of a number of light-influenced, EPR active components. The spectral characteristics of these components are indicative of iron-heme (both low and high-spin forms) and iron-sulfur (both oxidized and reduced) proteins and at least one other organic free radical distinct from P870'. The spectra varied for different strains of bacteria. Also, some of the signals detected in the whole cell organism were not detected in cell free preparations and the kinetics of the light influenced signal amplitudes were different in the whole cells than in chromatophores.

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Multiplicity of Electron Transport Reactions in Bacterial Photosynthesis

Cited by 52 publications

References 210 publications

Recollections

Recollections

Zur Struktur von Reaktionszentren in phototrophen Bakterien: eine Standortbestimmung

A Survey of Epr Investigations of Bacterial Photosynthesis

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