Section 5
Chapter 4,920

Characteristic temperature dependences of respiratory and photosynthetic electron transport activities in membrane preparations from anacystis nidulans grown at different temperatures

Peschek, G.A.; Muchl, R.; Kienzl, P.F.; Schmetterer, G.

Biochimica et Biophysica Acta 679(1): 35-43


ISSN/ISBN: 0005-2728
DOI: 10.1016/0005-2728(82)90252-3
Accession: 004919256

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Electron-transport activities supported by 7 different electron donor/acceptor couples in the light and in the dark, respectively, were measured in the particle preparations of the cyanobacterium (blue-green alga). A. nidulans after growth at 40, 30 and 25.degree. C. The Arrhenius plots of the photosynthetic electron-transport reactions between ascorbate (plus 2,6-dichlorophenolindophenol (DCIP)) and NADP+, diphenylcarbazide and DCIP, diaminodurene and benzyl viologen (O2), and the plot of the photooxidation of reduced horse heart cytochrome c showed a single discontinuity at .apprx. 24-25, 15-17 and 10-13.degree. C in membranes derived from cells grown at 40, 30 and 25.degree. C, respectively. The dark respiratory electron-transport reactions between NADPH, ascorbate (plus DCIP) or redcued horse heart cytochrome c and oxygen, and the reduction by horse heart cytochrome c of the aa3-type terminal oxidase as followed directly by wavelength spectrophotometry, all gave Arrhenius plots distinguished by 2 distinct breaks: The break at the higher temperature corresponded to the break also found in the Arrhenius plots of the photosynthetic reactions while an additional discontinuity was observed at 17-18, 8-9 and 5-6.degree. C in membranes prepared from cells grown at 40, 30 and 25.degree. C, respectively. The temperatures at which the discontinuities in the Arrhenius plots occurred depended on the temperature at which the cells had been grown; they were independent of the specific electron donors and acceptors employed. The characteristic features in Arrhenius plots of respiratory and photosynthetic electron-transport reactions are discussed in terms of lipid-base transitions in the cytoplasmic and the intracytoplasmic (thylakoid) membranes of A. nidulans. Implications for possible distinct sites of the respiratory and photosynthetic electron-transport systems in A. nidulans will be mentioned.

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