XVI A. Apoproteins of Photosystem I (PSI)
Electron transport Through PSI is mediated by the following components: P700 (presumably a Chl dimer), the primary electron acceptor A0 (a Chl molecule), the secondary electron acceptor A1 (of unknown chemical structure), and the three iron-sulfur centers, X, B, and A (all made up of 4 Fe-4 S clusters).
In the thylakoid membrane, the PSI complex is associated with light-harvesting pigment-protein antenna complexes. It appears to be made up of twelve different polypeptides designated: PSI-A (gene = psaA), PSI-B (gene = psaB), PSI-C (gene = psaC), PSI-D (gene = psaD), PSI-E (gene = psaE), PSI-F (gene = psaF), PSI-G (gene = psaG), PSI-H (gene = psaH), PSI-I (gene = psaI), PSI-J (gene = psaJ), PSI-K (gene = psaK), PSI-L (gene = psaL),