The roles of weak light,oxygen and dithiothreitol in the photoreactivation of the oxygen evolving center of tris-washed and 2, 6-dichlorophenol indophenol-treated chloroplasts |
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Authors: | Takashi Yamashita Takahiro Kobayashi Yasuhisa Morita Toshibumi Shoji |
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Institution: | (1) Institute of Biological Sciences, University of Tsukuba, 305 Tsukuba-shi, Ibaraki, Japan;(2) Present address: Kashiwazaki-Oguni High School, Oguni-cho, Kariwa-gun, 949-52 Niigata, Japan;(3) Niiza-kita High School, Ohwada, 352 Niiza-shi, Saitama, Japan;(4) Chichibubetsu High School, Chichibubetsu-cho, Uryu-gun, 078-21 Hokkaido, Japan |
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Abstract: | The inactivated O2-evolving center of Tris-washed chloroplasts was reactivated by DCPIP-treatment and photoreactivation in the presence of Mn2+, Ca2+, DTT and weak light. Many electron donors (Asc and reduced DCPIP, etc.) were found to be suitable substitutes for DTT. By studying the anaerobic inhibition of the reactivation, the electron acceptors O2, NADP+, etc. were also found to be essential factors in photoreactivation. Weak light stimulated the chloroplast electron transport from the above-mentioned electron donors to the electron acceptor and effected the photoreactivation. More than 280 electrons were transported to NADP+ in the anaerobic photoreactivation of one unit of an O2-evolving center with 400 Chl. Electron transport in the reactivation was inhibited by omitting DTT or Mn2+ ion, and by adding DCMU. The photoreactivated chloroplasts incorporated about 2 Mn by 400 Chl. Omission of DTT in the reactivation caused chloroplasts in the weak light to bind large amounts of excess Mn.Abbreviations Asc
ascorbate
- Chl
chlorophyll
- DCPIP
2, 6-dichlorophenol indophenol
- DPC
diphenyl carbazide
- DTT
dithiothreitol
- Fd
ferredoxin
- STN
a chloroplast preparation medium, containing 0.4 M sucrose, 0.05 M Tris-Cl and 0.01 M NaCl (pH 7.8 and 8.0)
- TMPD
tetramethyl-p-phenylenediamine |
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Keywords: | electron donors and acceptors Mn-incorporation N2-inhibition and O2-stimulation O2-evolution photoreactivation and Tris-washed chloroplasts |
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