Plastoquinones are effectively reduced by ferredoxin:NADP+ oxidoreductase in the presence of sodium cholate micelles. Significance for cyclic electron transport and chlororespiration.
The effect of sodium cholate and other detergents (Triton X-100, sodium dodecyl sulphate, octyl glucoside, myristyltrimethylammonium bromide) on the reduction of plastoquinones (PQ) with a different length of the side-chain by spinach ferredoxin:NADP(+) oxidoreductase (FNR) in the presence of NADPH has been studied. Both NADPH oxidation and oxygen uptake due to plastosemiquinone autoxidation were highly stimulated only in the presence of sodium cholate among the used detergents. Sodium cholate at the concentration of 20 mM was found to be the most effective on both PQ-4 and PQ-9-mediated oxygen uptake. The FNR-dependent reduction of plastoquinones incorporated into sodium cholate micelles was stimulated by spinach ferredoxin but inhibited by Mg(2+) ions. It was concluded that the structure of sodium cholate micelles facilitates contact of plastoquinone molecules with the enzyme and creates favourable conditions for the reaction similar to those found in thylakoid membranes for PQ-9 reduction. The obtained results were discussed in terms of the function of FNR as a ferredoxin:plastoquinone reductase both in cyclic electron transport and chlororespiration.
Department of Physiology and Biochemistry of Plants, Faculty of Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-387 Kraków, Poland.
Monika
M
Bojko
Jerzy
J
Kruk
Stanislaw
S
Wieckowski
D000693:Anaerobiosis; D002736:Chloroplasts / Q000502:physiology*; D004579:Electron Transport; D005287:Ferredoxin-NADP Reductase / Q000378:metabolism*; D008274:Magnesium / Q000737:chemistry / Q000494:pharmacology; D008823:Micelles; D009249:NADP / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D010971:Plastoquinone / Q000737:chemistry / Q000378:metabolism*; D020358:Sodium Cholate / Q000737:chemistry / Q000494:pharmacology*; D018724:Spinacia oleracea / Q000201:enzymology; D013501:Surface-Active Agents / Q000737:chemistry / Q000494:pharmacology
D008823:Micelles; D013501:Surface-Active Agents; D009249:NADP; D005287:Ferredoxin-NADP Reductase; D008274:Magnesium; D020358:Sodium Cholate; D010971:Plastoquinone