title: N-formylkynurenine as a marker of high light stress in photosynthesis.
abstract: Photosystem II (PSII) is the membrane protein complex that catalyzes the photo-induced oxidation of water at a manganese-calcium active site. Light-dependent damage and repair occur in PSII under conditions of high light stress. The core reaction center complex is composed of the D1, D2, CP43, and CP47 intrinsic polypeptides. In this study, a new chromophore formed from the oxidative post-translational modification of tryptophan is identified in the CP43 subunit. Tandem mass spectrometry peptide sequencing is consistent with the oxidation of the CP43 tryptophan side chain, Trp-365, to produce N-formylkynurenine (NFK). Characterization with ultraviolet visible absorption and ultraviolet resonance Raman spectroscopy supports this assignment. An optical assay suggests that the yield of NFK increases 2-fold (2.2 ± 0.5) under high light illumination. A concomitant 2.4 ± 0.5-fold decrease is observed in the steady-state rate of oxygen evolution under the high light conditions. NFK is the product formed from reaction of tryptophan with singlet oxygen, which can be produced under high light stress in PSII. Reactive oxygen species reactions lead to oxidative damage of the reaction center, D1 protein turnover, and inhibition of electron transfer. Our results are consistent with a role for the CP43 NFK modification in photoinhibition.
authors.affiliation: School of Chemistry and Biochemistry and Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
authors.forename: Tina M
authors.initials: TM
authors.lastname: Dreaden
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.forename: Sascha
authors.initials: S
authors.lastname: Rexroth
authors.forename: Bridgette A
authors.initials: BA
authors.lastname: Barry
mesh_terms: D000588:Amines / Q000378:metabolism; D000595:Amino Acid Sequence; D015415:Biomarkers / Q000378:metabolism; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D007737:Kynurenine / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism; D008027:Light; D010788:Photosynthesis / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D013059:Spectrum Analysis, Raman; D018724:Spinacia oleracea / Q000201:enzymology / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects; D013312:Stress, Physiological / Q000528:radiation effects*; D053719:Tandem Mass Spectrometry
chemical_list: D000588:Amines; D015415:Biomarkers; D045332:Photosystem II Protein Complex; D021122:Protein Subunits; C083100:photosystem II, chlorophyll binding protein, CP-43; C007772:N'-formylkynurenine; C076022:5-(biotinamido)pentylamine; D007737:Kynurenine; D001710:Biotin