Bacterial photophosphorylation and

H. Baltscheffsky, L.-V. von Stedingk, H. W. Heldt and M. Kligenberg (1966). Inorganic pyrophosphate formation in bacterial photophosphorylation. Science, 153, 1120-1122. 

Ajrfj+ = A P + Z pH where Z = 2.3 RT/ F The proton electrochemical potential (A Xjj+) difference across the coupled (energetically linked) plasma membrane in phototrophic bacteria plays an essential role in photophosphorylation and solute transport into bacterial cells. Therefore, the exact measurements of these quantities are required for studies of the mechanism of energy transduction. It was, for example, shown that R.ruhrum chrom-atophores, associated with a phospholipid-impregnated filter,... 

B.A.Melandri and A.Baccarini-Melandri, Bioenergetics of the early events of bacterial photophosphorylation, in Cation flux across biomembranes, Y.Mukohata and L.Packer eds.. Academic Press, New York (1979). 

B.A.Melandri, A.De Santis, G.Venturoli and A.Baccarini-Melandri, The rates of onset of photophosphorylation and of the protonic electrochemical potential difference in bacterial chromatophores, FEBS Lett. 95 130 (1978). 

A.Baccarini-Melandri, R.Casadio and B.A.Melandri, Thermodynamics and kinetics of photophosphorylation in bacterial chromatophores and their relation with the transmembrane electrochemical potential difference of protons, Eur.J.Biochem. 78 389 (1977). 

Venturole G and Melandri BA (1982) The localized coupling of bacterial photophosphorylation. Effect of Antimycin a and N,N-dicyclohexylcarbodiimide in chromatophores from Rhodopseudomonas sphaeroides, Ga, studied by single turnover event analysis, Biochim. Biophys. Acta 637, 447-456. 

Fig. 5.2. The photosynthetic membrane of a green sulfur bacterium. The light-activated bacte-riochlorophyll molecule sends an electron through the electron-transport chain (as in respiration) creating a proton gradient and ATP synthesis. The electron eventually returns to the bacteri-ochlorophyll (cyclic photophosphorylation). If electrons are needed for C02 reduction (via reduction of NADP+), an external electron donor is required (sulfide that is oxidised to elemental sulfur). Note the use of Mg and Fe.

The idea that oxidative phosphorylation and photophosphorylation systems are coupled with the transfer of a proton through the membrane was introduced by Mitchell (1966) and is now widely accepted. H+-ATPase (ATP synthase, F,Fo-ATPase) catalyzes ATP synthesis coupled to an electrochemical gradient and ATP hydrolysis driven by proton translocation in mitochondrial or bacterial membranes. (Boyer, 2001 Babcock and Wikstroem, 1992 Abraham et al., 1994 Allison, 1998 Ogilvie et al. 1997 Musser and Theg, 2000 Backgren et al., 2000 Arechada and Jones, 2001 Gibbsons et. al., 2000 and references therein). The enzyme from Escherichia coli consists of two parts, a water-... 

ATP synthase. An enzyme complex that forms ATP from ADP and phosphate during oxidative phosphorylation in the inner mitochondrial membrane or the bacterial plasma membrane, and during photophosphorylation in chloroplasts. Uses aproton gradient to chemiosmotically drive the synthesis. 

Paul, F. and Vignais, P. M. "Photophosphorylation in bacterial chromatophores entrapped in alginate gel improvement of the physical and biochemical properties of gel beads with barium chloride as gel-inducing agent" Enzyme Microb. Technol. 1980. 2 281-287. 

Chromatophores 1. plastids of higher plants Chloroplasts (see), Chromoplasts (see) and Leuco-plasts (see). 2. The photosynthetic organelle of Photosynthetic bacteria (see). Bacterial C. are intraplasmatic membranes originating from the cell membrane. They may exist as closed vesicles or as flattened stacks, whose membranes contain the photosynthetic pigments, and the components of photosynthetic electron transport and photophosphorylation. 

B.A.Melandri, R.Casadio and A.Baccarini Melandri, Energy levels and rates of photophosphorylation in bacterial chromatophores, in Photosynthesis 77, D.O.Hall, J.Coombs and T.W.Goodwin eds.. The Biochemical Society, London (1978). 

Incorporation of labeled amino acids by other components of the incubation medium can be excluded. Bacterial contamination of the chloroplast preparation is minimized by using sterile glassware and media. If the preparations are solubilized in 2% Triton X-100 at the end of the incubation, less than 0.1% of the radioactivity incorporated into protein is present in the pellet spun down at 10,000 for 10 min. This indicates that incorporation is not due to bacteria, nuclei, or whole leaf cells. The large stimulation of incorporation by light and the sensitivity to inhibitors of photophosphorylation argue for chloroplast, rather than mitochondrial, protein synthesis. If stored for 1 h at O C, the activity of the crude chloroplast suspensions decreases by about 50%. Therefore, we have not attempted to purify the chloroplasts from other cellular components present in the suspension. 

Moreover, it could be demonstrated that no ATP formation took place in preilluminated membranes which maintained a high and slowly decreasing Ay, unless one additional turnover of the electron transfer chain was elicited by a single turnover flash. Under those specific conditions, one flash alone was unable to drive ATP formation per se and the photophosphorylation was dependent upon the preenergization of the membrane. Under these conditions the decrease in the ATP yield accurately followed the decay of the membrane potential both parameters were destabilized by K and valino-mycin (Melandri et al.,1980). This observation, if one compares the single turnover behaviour of bacterial chromatophores to that in steady state of respiratory systems, indicate that both a competent Ap + and electron transport are conditions required for ATP formation. 

Nishimura M I to T and Chance B (1962) Studies on bacterial phosphox ylation. Ill A sensitive and rapid method of determination of photophosphorylation, Biochim. Biophys. Acta. 59, 177-182 Renger G Erixon K Do ring G and Wolff Ch (1976) Studies on the nature of the inhibitory effect of trypsin on the photosynthetic electron transport of system II in spinach chloropleists, Biochim. Biophys. Acta. 440, 278-286. 

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