Photoprotective role of NADPH:protochlorophyllide oxidoreductase A
| Autor: | Oscar Valdez, Frank Buhr, Majida El Bakkouri, Nikolai Lebedev, Christiane Reinbothe, Steffen Reinbothe, Stephan Pollmann |
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| Rok vydání: | 2008 |
| Předmět: |
Light
Photochemistry Globular protein Light-Harvesting Protein Complexes Biology chemistry.chemical_compound Pigment Protochlorophyllide Oxidoreductase NADH NADPH Oxidoreductases Binding site Plant Proteins chemistry.chemical_classification Binding Sites Multidisciplinary Singlet oxygen Mutagenesis Hordeum Biological Sciences Enzyme Energy Transfer chemistry Biochemistry Structural Homology Protein visual_art Mutagenesis Site-Directed visual_art.visual_art_medium Biophysics |
| Zdroj: | Proceedings of the National Academy of Sciences. 105:12629-12634 |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.0803950105 |
| Popis: | A homology model of NADPH:protochlorophyllide (Pchlide) oxidoreductase A (POR; E.C. 1.3.33.1) of barley is developed and verified by site-directed mutagenesis. PORA is considered a globular protein consisting of nine α-helices and seven β-strands. The model predicts the presence of two functionally distinctive Pchlide binding sites where the pigment is coordinated by cystein residues. The pigment bound to the first, high-affinity Pchlide binding site is used for the formation of the photoactive state of the enzyme. The pigment bound to the second, low-affinity Pchlide binding site is involved in the PORA:PORB interaction, allowing for resonance energy transfer between the neighboring PORs in the complex. In the in vitro reconstituted light-harvesting POR:Pchlide complex (LHPP), light absorbed by PORA-bound Pchlide b is transferred to PORB-bound Pchlide a . That induces the conversion of Pchlide a to chlorophyllide (Chlide) a . This energy transfer eliminates the possibility of Pchlide b photoreduction and prevents that excited triplet states of either Pchlides a or b accumulate and provoke singlet oxygen production. Together, our results provide a photoprotective role of PORA during greening. |
| Databáze: | OpenAIRE |
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