D1-D2 complex of the photosystem II reaction center from spinach Isolation and partial characterization

A pigment-protein complex consisting of D1 and D2 proteins, but depleted in the two lower molecular mass components of photosystem II, i.e. cytochrome b-559 and psbI gene product, has been isolated by octyl-β-D-glucopyranoside treatment of the purified photosystem II reaction center complex from spinach [(1987) Proc. Natl. Acad. Sci. USA 84, 109-112], followed by separation by high performance liquid chromatography using a gel-permeation column (TSK G3000 SW). The isolated complex is photochemically active in the photoreduction of intrinsic pheophytin a under steady-state illumination, in the presence of dithionite and methyl viologen, and exhibits pigment stoichiometries similar to those in the untreated reaction center, indicating that the D1-D2 complex provides the site of primary photochemistry in photosystem II, as well as the principal binding sites of pigments in the reaction center.