Identification of the Plastocyanin Binding Subunit of Photosystem I
A photosystem (PS) I complex being competent in mediating the electron transfer from plastocyanin (PCy) to ferredoxin is assembled from more than 7 subunits . The two large chlorophyll (chl) a containing subunits Ia and Ib are plastid encoded and carry the primary electron donor P700 and the electron acceptors A0, phylloquinone and Fe-SX. Subunit VII carries the electron acceptors Fe-SA and Fe-SB (reviewed in ). Subunit II has been shown by cross-linking to ensure the docking of ferredoxin to subunit VII , Subunit III appeared to be necessary for the electron transfer from PCy to PS I . This subunit does not carry a prosthetic group  and it is positively charged . Its attribution to a band in SDS-PAGE is ambiguous because subunit III and IV alter their relative position in different gel systems . Subunit III has been suggested to be identical with a subunit of 21 kDa  or a positively charged subunit of 9.7 kDa as deduced from the gene sequence . Several authors have questioned a role of subunit III. However, in a recent study  PCy was cross-linked to a PS I subunit of 19 kDa. The function of this subunit and the assignment to one of the PS I subunits remains to be established.
KeywordsMethyl Viologen Primary Electron Donor Stroma Lamella Negative Surface Charge Density Peptide Deduce Sequence
Unable to display preview. Download preview PDF.
- Malkin, R. (1987) In: The Light Reactions. Topics in Photosynthesis, Vol. 8 (Barber, J., ed.), pp. 495–525, Elsevier, AmsterdamGoogle Scholar