An Alternative Electron Transfer Pathway Mediated by Chloroplast Envelope |
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Authors: | Murata Yoshinori; Takahashi Masaaki |
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Institution: | Department of Applied Biological Chemistry, Faculty of Agriculture, Osaka Prefecture University 1-1, Gakuen-cho, Sakai, Osaka, 599-8531 Japan |
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Abstract: | Localization of redox active substance(s) in chloroplast envelopeswas revealed by means of the oxidation of Cyt c by isolatedouter and inner envelope preparations. Irradiated chloroplastsreduced extra-chloroplastic Cyt c probably by an envelope electrontransfer chain. The rate was saturated at a level of about 10µmol (mg Chl)1 h1 under weak light of 10µEm2 s1. Cyt c photoreduction was inhibited by DCMUbut not by 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB)indicating that the plastoquinone site is the junction of photosyntheticelectron transfer chain to envelope redox substance. Completesuppression of the non-cyclic photophosphorylation of thylakoidsby the presence of envelope membranes indicates that there isan alternative electron transfer path-way in envelope membranesthat bypasses over the pH-forming plastoquinone shuttle in thephotosynthetic electron transfer chain.
1 Present address: Photosynthesis Research Laboratory, Instituteof Physical and Chemical Research (RIKEN), Wako, Saitama, 351-0198Japan. |
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