Degradation of the D1 protein of photosystem-II reaction centre by ultraviolet-B radiation requires the presence of functional manganese on the donor side.
The in vivo effects of ultraviolet-B radiation (280-320 nm) on photosystem-II activity and degradation of the D1 protein are investigated and compared with the in vitro results on isolated thylakoids and other detergent-extracted photosystem-II preparations. A cleavage site in the second transmembrane segment of the D1 protein, giving rise to a 20-kDa C-terminal and a 13-kDa N-terminal fragment pair, is detected after irradiation of entire leaves as well as in all photosystem-II preparations, irrespective of their actual ability to evolve oxygen but depending on the presence of Mn ions associated with the water-splitting system. Damage to the plastoquinone moiety, observed by other authors, is confirmed and is proposed to be responsible for the impairment of electron-transport activity, but not for the observed cleavage of the D1 protein.
Barbato
R
R
Dipartimento di Biologia, Università di Padova, Italy.
Frizzo
A
A
Friso
G
G
Rigoni
F
F
Giacometti
G M
GM
D001665:Binding Sites; D004579:Electron Transport; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008970:Molecular Weight; D010100:Oxygen / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*; D045332:Photosystem II Protein Complex; D018724:Spinacia oleracea; D014466:Ultraviolet Rays
D010446:Peptide Fragments; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D008345:Manganese; D010100:Oxygen