Abstract
Calcium (Ca(2+)) and redox signalling play important roles in acclimation processes from archaea to eukaryotic organisms. Herein we characterized a unique protein from Chlamydomonas reinhardtii that has the competence to integrate Ca(2+)- and redox-related signalling. This protein, designated as calredoxin (CRX), combines four Ca(2+)-binding EF-hands and a thioredoxin (TRX) domain. A crystal structure of CRX, at 1.6 Å resolution, revealed an unusual calmodulin-fold of the Ca(2+)-binding EF-hands, which is functionally linked via an inter-domain communication path with the enzymatically active TRX domain. CRX is chloroplast-localized and interacted with a chloroplast 2-Cys peroxiredoxin (PRX1). Ca(2+)-binding to CRX is critical for its TRX activity and for efficient binding and reduction of PRX1. Thereby, CRX represents a new class of Ca(2+)-dependent 'sensor-responder' proteins. Genetically engineered Chlamydomonas strains with strongly diminished amounts of CRX revealed altered photosynthetic electron transfer and were affected in oxidative stress response underpinning a function of CRX in stress acclimation.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Binding Sites
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Calcium / chemistry*
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Calcium / metabolism
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Calcium-Binding Proteins / chemistry*
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Calcium-Binding Proteins / genetics
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Calcium-Binding Proteins / metabolism
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Calmodulin / chemistry
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Calmodulin / genetics
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Calmodulin / metabolism
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Chlamydomonas reinhardtii / genetics*
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Chlamydomonas reinhardtii / metabolism
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Chloroplasts / genetics*
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Chloroplasts / metabolism
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Cloning, Molecular
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Crystallography, X-Ray
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Electron Transport
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Escherichia coli / genetics
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Escherichia coli / metabolism
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Gene Expression
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Gene Expression Regulation, Plant*
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Models, Molecular
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Oxidation-Reduction
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Peroxiredoxins / chemistry
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Peroxiredoxins / genetics
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Peroxiredoxins / metabolism
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Photosynthesis / genetics
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Plant Proteins / chemistry*
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Plant Proteins / genetics
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Plant Proteins / metabolism
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Plants, Genetically Modified
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Protein Binding
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Protein Conformation, alpha-Helical
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Protein Conformation, beta-Strand
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Protein Folding
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Protein Interaction Domains and Motifs
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Recombinant Proteins / chemistry
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Signal Transduction
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Thioredoxins / chemistry*
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Thioredoxins / genetics
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Thioredoxins / metabolism
Substances
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Calcium-Binding Proteins
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Calmodulin
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Plant Proteins
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Recombinant Proteins
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Thioredoxins
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Peroxiredoxins
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Calcium