biostudies-literatureUnknown7Hochmal AKCalcium (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 ofNature communications11847https://www.ebi.ac.uk/biostudies/studies/S-EPMC4911631biostudies-literatureCalredoxin represents a novel type of calcium-dependent sensor-responder connected to redox regulation in the chloroplast.PMC4911631Tanaka HScholz MFufezan CHochmal AKGabelein PMutoh RHuang KFinazzi GHippler MZinzius KSchulze SNordhues APetroutsos DCharoenwattanasatien ROffenborn JNKurisu GLiu GfalseCalredoxin represents a novel type of calcium-dependent sensor-responder connected to redox regulation in the chloroplast.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 of2016-01-01T00:00:00Z2016 Jun2026-05-30T06:53:27.877Z2019-03-27T02:16:18ZS-EPMC49116312729704110.1038/ncomms11847