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

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Abstract
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.