Tentative identification of the apoproteins of iron‐sulfur centers of Photosystem I

A newly purified Photosystem (PS) I particle is described, with still active iron‐sulfur acceptors: A, B and X. Apart from the apoprotein of P700, 3 other main polypeptides of this particle are located at 20, 17 and 10 kDa, and two minor ones are detectable at 16.5 and 8 kDa. Both in vivo 35S labeling and carboxymethylation with iodo[14C]acetate show that most of the cysteine residues are located in the 8‐kDa band. The amino acid composition of this band reveals important common features with small iron‐sulfur proteins of the ferredoxin type.