Three-dimensional structure of the higher-plant photosystem II reaction centre and evidence for its dimeric organization in vivo.

The three-dimensional structure of photosystem II (PSII) has been determined by conventional transmission electron microscopy and computerized three-dimensional reconstruction. Both the complete system and that lacking the oxygen-evolving complex have been analyzed. The PSII complex has a four-lobed structure with twofold symmetry. An estimate of the molecular mass and the results of Deriphat/PAGE analysis suggest that a reaction centre is present in each half of the structure resolved by electron microscopy. Stepwise removal of components of the complex showed that the removal of CP47 (a 47-kDa chlorophyll-protein complex) induces monomerization of PSII, which indicates the importance of this subunit for the dimeric structure.