Characterization of a 41 kDa photoinhibition adduct in isolated photosystem II reaction centres

When isolated reaction centres of photosystem II are subjected to photoinhibitory illumination, a 41 kDa SDS-PAGE band is observed under all experimental conditions. The same band is also found, together will lower molecular weight fragments of the D1 protein, in whole thylakoids and in all PSII sub-particles investigated up to now. In the case of isolated reaction centres the 41 kDa band is represented by a heterodimer of the D1 polypeptide and the α-subunit of cytochrome b 559. The cross-linkage between D1 and α-cyl b 559 involves a region on D1 between the N-terminal residue and Arg·225, and is an early event in photo-induced damage to the D1 protein.