New herbicide‐binding site in the photosynthetic electron‐transport chain

FEBS Letters

Itoh, Shigeru¹  Iwaki, Masayo¹ 

[1] National Institute for Basic Biology, 38 Nishigonaka, Myodaiji,azaki 444, Japan

关键词: Photosystem I;    Quinone;    Phylloquinone;    Vitamin K-1;    Herbicide;    Reaction center;    DBMIB;    dibromothymoquinone;    DCMU;    3-(3;    4-dichlorophenyl)-1;    1-dimethylurea;    HOQNO;    2-heptyl-4-hydroxyquinoline N-oxide;    prometone;    2;    4-bis(isopropyl-amino)-6-(methoxy)-s-triazine;    prometryne;    2;    4-bis(isopropyl-amino)-6-(methylthio)-s-triazine;    PS;    photosystem;    Qφ site;    PS I phylloquinone-binding site;   

DOI  :  10.1016/0014-5793(89)80773-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The binding of herbicides to the phylloquinone-(primary electron acceptor A₁)-binding site in green plant photosystem (PS) I reaction centers is shown. Dissociation constants (K _d) of various herbicides to the phylloquinone-binding site were estimated by analyzing their competitive inhibition of the reconstitution of the phylloquinone analogue, menadione (vitamin K₃), to the phylloquinone-extracted spinach PS I particles. The phylloquinone-binding site was found to bind o-phenanthroline (K _d = 1.2 × 10⁻⁴ M), but only weak binding was observed with atrazine (K _d > 10⁻² M), although both are known to bind specifically to the quinone-(Q_B)-binding site in reaction centers of purple photosynthetic bacteria or PS II. The inhibitors of the cytochrome b/c ₁(ƒ) complex, myxothiazol (K _d=9.5 × 10⁻⁶ M) or antimycin A (K _d = 2.8 × 10⁻⁶ M), also strongly bound to the phylloquinone site. This is the first report showing that the PS I reaction center complex also has a herbicide-binding site, although the site is probably not sensitive in vivo to these herbicides due to its higher affinity for phylloquinone than herbicides. The inhibitor specificity of the PS I phylloquinone site is different from that of the other quinone-functioning sites in the photosynthetic or respiratory electron-transfer chain, suggesting it to have a unique structure.

【 授权许可】

Unknown