Structure of Photosystem I: Suggestions on the docking sites for plastocyanin, ferredoxin and the coordination of P700

Photosystem I of Synechococcus elongatus was crystallized showing maximal diffraction to 4 Å resolution (Witt et al. (1988) Ber. Bunsenges. Phys. Chem. 92, 1503-1506). The crystal structure has been determined at a resolution of 6 Å (Krauß et al. (1993) Nature 361, 326-331). Based on this structure, docking sites for plastocyanin and ferredoxin are proposed. The arrangement of helices is analysed in terms of hydrophobicity plots and homology to the reaction center of purple bacteria. A possible coordination of the primary donor P700 by the helices in subunits A and B is suggested based on the relative three-dimensional arrangement of the helices.