1. CHAPERONIN 20 mediates iron superoxide dismutase (FeSOD) activity independent of its co-chaperonin role in Arabidopsis chloroplasts.
- Author
-
Kuo WY, Huang CH, Liu AC, Cheng CP, Li SH, Chang WC, Weiss C, Azem A, and Jinn TL
- Subjects
- Agrobacterium tumefaciens genetics, Agrobacterium tumefaciens metabolism, Arabidopsis genetics, Arabidopsis Proteins genetics, Chloroplasts genetics, Enzyme Activation, Gene Expression Regulation, Enzymologic, Gene Expression Regulation, Plant, Gene Silencing, Green Fluorescent Proteins metabolism, Group I Chaperonins genetics, Solanum lycopersicum genetics, Solanum lycopersicum metabolism, Plants, Genetically Modified genetics, Plants, Genetically Modified metabolism, Protein Interaction Mapping, Recombinant Fusion Proteins metabolism, Saccharomyces cerevisiae genetics, Saccharomyces cerevisiae metabolism, Superoxide Dismutase genetics, Transfection, Two-Hybrid System Techniques, Arabidopsis enzymology, Arabidopsis Proteins metabolism, Chloroplasts enzymology, Group I Chaperonins metabolism, Superoxide Dismutase metabolism
- Abstract
Iron superoxide dismutases (FeSODs; FSDs) are primary antioxidant enzymes in Arabidopsis thaliana chloroplasts. The stromal FSD1 conferred the only detectable FeSOD activity, whereas the thylakoid membrane- and nucleoid-co-localized FSD2 and FSD3 double mutant showed arrested chloroplast development. FeSOD requires cofactor Fe for its activity, but its mechanism of activation is unclear. We used reversed-phase high-performance liquid chromatography (HPLC), gel filtration chromatography, LC-MS/MS, protoplast transient expression and virus-induced gene silencing (VIGS) analyses to identify and characterize a factor involved in FeSOD activation. We identified the chloroplast-localized co-chaperonin CHAPERONIN 20 (CPN20) as a mediator of FeSOD activation by direct interaction. The relationship between CPN20 and FeSOD was confirmed by in vitro experiments showing that CPN20 alone could enhance FSD1, FSD2 and FSD3 activity. The in vivo results showed that CPN20-overexpressing mutants and mutants with defective co-chaperonin activity increased FSD1 activity, without changing the chaperonin CPN60 protein level, and VIGS-induced downregulation of CPN20 also led to decreased FeSOD activity. Our findings reveal that CPN20 can mediate FeSOD activation in chloroplasts, a role independent of its known function in the chaperonin system., (© 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.)
- Published
- 2013
- Full Text
- View/download PDF