Maize Photosystem I : Identification of the Subunit which Binds Plastocyanin

Photosystem I (PSI) has been isolated from mesophyll chloroplasts of mature maize leaves. The isolated PSI (PSI-200) was used as starting material for preparing an antenna-depleted core (PSI-100). Both of these preparations appear to be quite analogous to PSI complexes isolated from other plant tissue sources, such as those from C3 plants, as judged from NADP photoreduction assays, immunoblotting, and the ability of the complexes to form a covalent crosslinked product with spinach plastocyanin. The study suggests that the PSI complex from a C4 plant is similar to that isolated from a C3 plant in that both contain the plastocyanin docking protein although the apparent molecular weight of these respective subunits differ slightly.