title: Degradation of D2 protein due to UV-B irradiation of the reaction centre of photosystem II.
abstract: Exposure of isolated reaction centres of photosystem II to UV-B radiation generates specific breakdown products of the D2 protein. When the quinone, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone is present a 22 kDa fragment containing the N-terminus of the mature protein is generated. Concomitant with the appearance of the N-terminal fragment, two fragments containing the C-terminus of the D2 protein having apparent molecular masses around 10-12 kDa are observed. It is concluded that the primary cleavage occurs in the hydrophilic loop linking putative transmembrane segments IV and V. No such cleavage was observed when silicomolybdate was used as an electron acceptor, suggesting that this UV-B damage is dependent on binding of the added quinone to the QA site.
authors.affiliation: Dipartimento di Biologia, Universita di Padova, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Friso
authors.forename: R
authors.initials: R
authors.lastname: Barbato
authors.forename: G M
authors.initials: GM
authors.lastname: Giacometti
authors.forename: J
authors.initials: J
authors.lastname: Barber
mesh_terms: D016227:Benzoquinones / Q000378:metabolism; D001665:Binding Sites; D003991:Dibromothymoquinone / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D015151:Immunoblotting; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism* / Q000528:radiation effects; D045332:Photosystem II Protein Complex; D012697:Serine Endopeptidases / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D016227:Benzoquinones; D010446:Peptide Fragments; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D003991:Dibromothymoquinone; C004532:quinone; D012697:Serine Endopeptidases; C028344:glutamyl endopeptidase