The PSI-E subunit of photosystem I binds ferredoxin:NADP+ oxidoreductase

AbstractA photosystem I complex containing the polypeptides PSI-A to PSI-L, light-harvesting complex I and ferredoxin:NADP+ oxidoreductase has been isolated from barley using the non-ionic detergent n-decyl-β-d-maltopyranoside. The ratio between bound forredoxin:NADP+ oxidoreductase and P700 is 0.4 ± 0.2. The complex is highly active in catalyzing light-induced transfer of electrons from plastocyanin to NADP+ at rates of 280±150 and 1800 ± 800, μmol NADPH/(mg chl h), without and in the presence of saturating amounts of exogenously added ferredoxin:NADP+ oxidoreductase, respectively. Endogenously bound ferredoxin:NADP+ oxidoreductase interacts with the PSI-E subunit as demonstrated by cross-linking experiments using two different types of cross-linkers and identification of the products by Western blotting and the use of monospecific antibodies