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p-nitroacetophenoxime N-methylcarbamate,a new electron acceptor in isolated thylakoids |
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| Authors: | M. Tissut G. Mrlina E. Genies J.P. Calmon |
| Affiliation: | 1. Laboratoire de Physiologie cellulaire végétale, ERA CNRS 847, Université de Grenoble I, BP 68, 38 402, Saint Martin d''Hères Cédex, France;2. Laboratoire de Chimie organique biologique et de Physicochimie des sols, Institut National Polytechnique de Toulouse, 145, avenue de Muret, 31 076, Toulouse cédex, France;3. Laboratoires de Chimie, Laboratoire d''Electrochimie Organique et Analytique (LA CNRS 321), Centre d''Etudes Nucléaires de Grenoble, Département de Recherche Fondamentale, BP 85 X, 38 041, Grenoble cédex, France |
| Abstract: | p-Nitroacetophenoxime N-methylcarbamate (MCPNA) is a rather potent inhibitor of the electron transfer in spinach class A chloroplasts. In isolated thylakoids, MCPNA is an electron acceptor at the level of photosystem I (PS I). It inhibits O2 evolution in the presence of NADP and ferredoxin but not the reduction of ferricyanide. MCPNA is active as an acceptor between 3 μM and 100 μM. At concentrations higher than 300 μM, inhibition of photosystem II (PS II) occurs. MCPNA has no uncoupling effect on photophosphorylation. Reduction of MCPNA by thylakoids in the presence of light is in accordance with the E′o of this compound (??0.57 V) and is followed by an electron transfer to O2. This reaction probably explains the inhibitory effect of MCPNA on class A chloroplasts. |
| Keywords: | chloroplasts electron transfer methylviologen thylakoids spinach DBMIB Diuron (DCMU) 3-(3,4-dichlorophenyl)-1,1-dimethylurea DPIP dichlorophenolindophenol concentration of the product giving a 50% inhibition MCPNA MOPS morpholinopropane sulfonic acid MV methylviologen PS I photosystem I PS II photosystem II TMPD |
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