Bacteria photosynthetic phosphorylation

Photoautotrophic bacteria 8 Photofootprinting 266 Photorespiration 707 Photosynthesis 506,517, 705 Photosynthetic bacteria 7 Photosynthetic phosphorylation 303, 517 Photosynthetic reaction centers 71 Phthaldialdehyde 120s Phycoerythrin 22 Phycomycetes 20... 

Arnon (1951). Formation of ATP in the light, called photosynthetic phosphorylation, was discovered by Frenkel (1954) in particles from photosynthetic bacteria, and by Arnon et al. (1954) in isolated chloroplasts. 

The above is a very simplified account of the chemiosmotic theory and a number of the details of oxidative phosphorylation remain to be elucidated, in particular the molecular mechanism of proton pumping and the exact mechanism of action of the ATPase. However, the basic principles of the theory are now widely accepted. This theory is also able to account for photosynthetic phosphorylation in chloroplasts and for the synthesis of ATP by bacteria. 

Ferredoxins are proteins containing equal numbers of iron and sulphur atoms in each active centre. They transfer electrons below the potential of the hydrogen electrode. The 8Fe-8S ferredoxins are associated with the most primitive organisms (obligate anaerobic fermenters and photosynthesizers) where they are used for electron-transfer in the pyruvate phosphoroclastic system the 4Fe-4S types probably came next in evolution and are found in sulphate- and nitrate-reducing bacteria. The later zFe-zS ferredoxins are found in plants and animals where they are essential for oxidative phosphorylation in mitochondria, for photosynthetic phosphorylation in chloroplasts, and for the synthesis of catecholamine hormones. The individual types are distinguished by e.s.r. and Mossbauer spectra. For a review, see Hall and Evans (1969). 

Frenkel, A. 1954. Light-induced phosphorylation by cell-free preparations of photosynthetic bacteria. J. Am. Chem. Soc. 76 5568-5569. 

ATP synthesis in photosynthetic organisms, i.e., photophosphorylation, was discovered nearly fifty years ago. In 1954 Albert Frenkel" using membrane vesicles of purple bacteria, and Daniel Arnon and coworkers, using spinach chloroplasts, reported light-induced phosphorylation almost simultaneously and opened up a new era in photosynthesis research. These investigations not only established the conditions necessary for ATP synthesis by photosynthetic membranes, but also established that ATP synthesis is closely related to electron transport. 

DE Fleischman and RK Clayton (1968) The effect of phosphorylation uncouplers and electron transport inhibitors upon spectral shifts and delayed light emission of photosynthetic bacteria. Photochem Photobiol 8 287-298... 

Non-sulfur, purple, photosynthetic bacteria, Rho do spirillum rub-rum and Rhodopseudomonas spheroides172 also possess a PEP-de-pendent D-fructose phosphotransferase. Two protein fractions are required for D-fructose phosphorylation. In contrast to PEP-depend-ent, phosphotransferase systems isolated from other bacteria, the aforementioned two organisms have one active protein fraction tightly associated with the membrane fraction, while another in the crude extract is solubilized by extraction with water, and has a molecular weight of about 200,000. There is no evidence for the presence of a phosphate-carrier protein of low molecular weight like HPr.171,173 The... 

Oxidative phosphorylation has been observed in particles derived from both bacteria and plants in addition to those derived from animal cells. A special type of oxidative phosphorylation has been found in photosynthetic organisms. Particles that contain the photochemical apparatus also appear to contain a series of enzymes that can recombine the products of photolysis and couple this process with the esterification of phosphate. The photochemical system is distinct from more conventional oxidative enzymes that use molecular oxygen as an electron acceptor. 

The main principles of membrane phosphorylation are the same in chloroplasts, mitochondria, and photosynthetic bacteria. In this section, in order to analyze the role of protonmotive force in the processes of energy transduction in biomembranes, we will focus our attention on the consideration of proton-transport processes in chloroplasts. In thylakoids the ApH is the main component of transmembrane difference in electrochemical potentials of hydrogen ions, AjuH+ = Acp — 2.3(RT/F)ApH. The conductivities of the thylakoid membrane for the majority of cations (Mg ", Na ), existing... 

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