The structures of photosystem II, with the water-oxidizing Mn4CaO5-cluster fully removed and in an intermediate assembly state, show that photoassembly is facilitated by perfectly pre-arranged protein ligands of the five metal ions.
The structure of the photosystem I (PSI) complex from Synechocystis is determined, and reaction center subunits engineered to resemble a viral PSI are found to promote promiscuous electron acceptor properties.