SITE OF MANGANESE FUNCTION IN PHOTOSYNTHETIC ELECTRON TRANSPORT SYSTEM

被引:70
作者
ITOH, M
YAMASHIT.K
NISHI, T
KONISHI, K
SHIBATA, K
机构
[1] The Tokugawa Institute for Biological Research, Mejiromachi, Tokyo Postal address
[2] Tokyo Institute of Technology, Meguroku, Tokyo
关键词
D O I
10.1016/0005-2728(69)90029-2
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The effects of Mn2+ on aerobic photobleaching of carotenoids, on photoreduction of 2,6-dichlorophenolindophenol (DCIP) and on fluorescence above 600 mμ of spinach chloroplasts washed with 0.8 M Tris-HC1 buffer were investigated. Carotenoids (mostly carotenes, lutein and violaxanthin) in the Tris-washed chloroplasts were irreversibly bleached by illumination with red light, while carotenoids in normal chloroplasts prepared with a low concentration of Tris-HC1 underwent no bleaching upon illumination. The photobleaching of carotenoids observed with Tris-washed chloroplasts was inhibited by Mn2+ (MnCl2 or MnSO4) as well as by some inhibitors of the Hill reaction such as dichlorophenyl-1,1-dimethylurea (DCMU), methylthio-4,6-bis-isopropylamino-s-triazine and o-phenanthroline or by reducing agents such as ascorbate plus tetramethyl-p-phenylene diamine (TMPD). DCIP photoreduction, which was deactivated by Tris, was reactivated to 50-80% of the rate for normal chloroplasts upon addition of Mn2+. The restored photoreduction of DCIP was inhibited by DCMU and carbonylcyanide m-chlorophenylhydrazone (CCCP). The steady-state fluorescence yield of normal chloroplasts measured at room temperature was lowered by Tris treatment, and the decreased yield was restored by adding Mn2+ as well as ascorbate plus TMPD. CCCP also lowered the yield; the yield was recovered by adding ascorbate plus TMPD. Determination of manganese in normal and Tris-washed chloroplasts showed that 30% of the manganese in chloroplast was removed with Tris. It was postulated that Mn2+ functions in the electron transport on the oxidizing side of Photosystem II at a site between water and an electron carrier (Y). CCCP as well as Tris inhibits the reduction of Y+ by Mn2+, and carotenoids are oxidized by Y+ which is reduced by ascorbate plus TMPD. © 1969.
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页码:509 / &
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