The highly purified PS II reaction center complex with 47, 43, 32, 30 and 9 kDa (and 4.5 kDa) polypeptides was subjected to iodo-labeling to identify the polypeptide(s) participating on the donor side of the photosystem. The 32 kDa component (D2) and the aggregate(s) of about 60 kDa were exclusively labeled in the dark, suggesting the presence of a dark-stable oxidizing component on this polypeptide. Illumination of the complex in the presence of 2,6-dichlorophenolindophenol and iodide resulted in the preferential iodination of the 30 kDa component (D1) and the aggregate(s), but not the 47 kDa polypeptide. This iodo-labeling was completely inhibited by the addition of an electron donor, 1,5-diphenylcarbazide. From these results, it is concluded that the site of photooxidation of iodide, and presumably the site of Z binding, is located on or near the herbicide-binding polypeptide, D1, in the PS II reaction center complex.
- Photosystem II Reaction center Iodo-labeling Secondary electron donor Herbicide-binding protein
ASJC Scopus subject areas
- Structural Biology
- Molecular Biology
- Cell Biology