title: Effect of moderate UV-B irradiation on Synechocystis PCC 6803 biliproteins.
abstract: In the present study, we investigated the mechanism of UV-B radiation induced damage to the light harvesting apparatus of the cyanobacterium Synechocystis 6803. Liquid chromatography analysis and spectroscopy investigations performed on phycobilisomes or isolated biliproteins irradiated with moderate UV-B intensity (1.3 W/m(2)) revealed rapid destruction of beta-phycocyanin and a slower damage of the other biliproteins, alpha-phycocyanin and both alpha and beta-allophycocyanin. EPR spin trapping measurements revealed that carbon centered adducts of the spin trap DMPO were formed. This evidence indicates that free radicals produced from bilins probably attack the polypeptide chain of protein inducing its degradation. Our results show that the bilin chromophore is the main target of UV-B irradiation, causing structural changes, which in turn induce reaction of the chromophore with atmospheric oxygen and lead to production of reactive radicals. Our results also demonstrate that beta-phycocyanin is the most affected biliprotein, probably due to the presence of two bilins as chromophore.
authors.affiliation: Department of Environmental Sciences, Tuscia University, Largo dell'Università, 01100 Viterbo, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Rinalducci
authors.forename: Eva
authors.initials: E
authors.lastname: Hideg
authors.forename: Imre
authors.initials: I
authors.lastname: Vass
authors.forename: Lello
authors.initials: L
authors.lastname: Zolla
mesh_terms: D001426:Bacterial Proteins / Q000528:radiation effects*; D002851:Chromatography, High Pressure Liquid; D004578:Electron Spin Resonance Spectroscopy; D045342:Light-Harvesting Protein Complexes / Q000528:radiation effects*; D045524:Phycobilisomes / Q000528:radiation effects; D010798:Phycocyanin / Q000528:radiation effects; D013053:Spectrophotometry; D046939:Synechocystis / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045524:Phycobilisomes; C002497:allophycocyanin; D010798:Phycocyanin