Photosystem II

Model of the acceptor side of photosystem II core from Howie Robinson (1)

The structure is a model based on use of the bacterial reaction center as a template.

In the initial view, the protein is oriented with the acceptor side (stroma facing domain) up, and the donor-side (lumen facing domain) down. The D1 subunit is colored green (helix D) and orange (helix E), and the D2 subunit blue (helix D) and blue-green (helix E). The chromophores are shown as ball and stick models, colored as follows: pheophytin of D2, green-blue; PQ_A, yellow; PQ_B, CPK-colors.

Reload in initial configuration, with side chains showing.

The acceptor side

Zoom in on the acceptor side. The residues highlighted are those within 7.5 Å of the Q_B plastoquinone. Residues shown as thick sticks are changed in herbicide resistant mutants of green plants or Chlamydomonas, putative ligands, or residues which change the kinetics of electron transfer at the Q_B-site on mutation (H215, V219, A251, H252, F255, G256, R257, S264, H272, L275, - color-coded by amino acid type). The plastoquinones are colored yellow (Q_A) or orange (Q_B), with O- and H-atoms in CPK, Fe red. The D1 and D2 subunits are represented by ribbon models colored cyan or yellow respectively.

(See panel at top left for amino acid color coding)

Crofts, A.R., Robinson, H.H., Andrews, K., Van Doren, S. and Berry, E. (1987) Catalytic sites for reduction and oxidation of quinones. In "Cytochrome Systems: Molecular Biology and Bioenergetics", Papa, S., Chance, B. and Ernster, L., eds. pp. 617-624, Plenum Publ., New York.