Np. Mishra et al., DESTRUCTIVE ROLE OF SINGLET OXYGEN DURING AEROBIC ILLUMINATION OF THEPHOTOSYSTEM-II CORE COMPLEX, Biochimica et biophysica acta. Bioenergetics, 1186(1-2), 1994, pp. 81-90
Strong illumination of the Photosystem II (PS II) core complex, at 35
degrees C under aerobic conditions, resulted in rapid inactivation of
electron transport activity, and pigment photobleaching which was foll
owed by the degradation of the D1 polypeptide. Concomitant with D1 deg
radation there was a significant disappearance of the 43 and 29 kDa Ch
l binding proteins and an appearance of high-molecular-weight species
originating from the cross-linking of other PS II proteins with the D1
polypeptide and/or D1 fragments. Strict anaerobic conditions during i
llumination almost completely prevented pigment photobleaching and pro
tein degradation and subsequent cross-linking. The presence of singlet
oxygen scavengers, histidine and rutin, during illumination, signific
antly protected against photoinduced damage to the PS II complex, sugg
esting an involvement of singlet oxygen in the destructive process. Si
nglet oxygen-generating chemicals led to similar pigment bleaching and
protein cross-linking. We propose that singlet oxygen, which is gener
ated during aerobic illumination of the PS II complex, is responsible
for the photobleaching of photosynthetic pigments, D1 protein degradat
ion and protein cross-linking.