Calredoxin represents a novel type of calcium-dependent sensor-responder connected to redox regulation in the chloroplast

• DOI: 10.1038/ncomms11847
• Publication Date: 2016-06-14T09:49:26Z
• Authors: Ana Karina Hochmal; Karen Zinzius; Ratana Charoenwat...; Philipp Gäbelein; Risa Mutoh; Hideaki Tanaka; Stefan Schulze; Gai Liu; Martin Scholz; André Nordhues; Jan Niklas Offenborn; Dimitris Petroutsos; Giovanni Finazzi; Christian Fufezan; Kaiyao Huang; Genji Kurisu; Michael Hippler
• Keywords: Models, Molecular; Protein Conformation, alpha-Helical; chlamydomonas reinhardtii; Redox signaling; Chloroplasts; [SDV]Life Sciences [q-bio]; [SDV.BBM]Life Sciences [q-bio]/Biochemistry; Gene Expression; Crystallography, X-Ray; Biochemistry; Stress acclimation; Gene Expression Regulation, Plant; Cloning, Molecular; Photosynthesis; Biokemi; Plant Proteins; 0303 health sciences; Molekylärbiologi; chloroplaste; Subcellular localization; Q; Biochemistry and Molecular Biology; Plants, Genetically Modified; Thioredoxin domain; Oxidation-Reduction; Protein Binding; 570; Algae; CRX; Science; 610; Calredoxin; Chloroplast; Article; Electron transfer; Electron Transport; 03 medical and health sciences; Calmodulin; transfert d'électrons; Escherichia coli; [SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology; acclimatation; Molecular Biology; calcium; Binding Sites; Protein; Crystal structure; Calcium-Binding Proteins; stress oxydatif; Peroxiredoxins; Oxidative stress; Calcium; Biokemi och molekylärbiologi; Chlamydomonas reinhardtii

AbstractCalcium (Ca2+) 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 Ca2+- and redox-related signalling. This protein, designated as calredoxin (CRX), combines four Ca2+-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 Ca2+-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). Ca2+-binding to CRX is critical for its TRX activity and for efficient binding and reduction of PRX1. Thereby, CRX represents a new class of Ca2+-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.