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The stress-associated protein SAP12 belongs to the stress-associated protein (SAP) family with 14 members in Arabidopsis thaliana. SAP12 contains two AN1 zinc fingers and was identified in diagonal 2D redox SDS-PAGE as a protein undergoing major redox-dependent conformational changes. Its transcript was strongly induced under cold and salt stress in a time-dependent manner similar to SAP10, with high levels after 6 h and decreasing levels after 24 and 48 h. The tran-script regulation resembled those of the stress marker peroxiredoxin PrxIID at 24 and 48 h. Recombinant SAP12 protein showed redox-dependent changes in quateary structure as visualized by altered electrophoretic mobility in non-reduc-ing SDS polyacrylamide gel electrophoresis. The oxidized oligomer was reduced by high dithiothreitol concentrations, and also by E. coli thioredoxin TrxA with low dithiothreitol (DTT) concentrations or NADPH plus NADPH-dependent thioredoxin reductase. From Weste blots, the SAP12 protein amount was estimated to be in the range of 0.5 ng μg-1 leaf protein. SAP12 protein decreased under salt and cold stress. These data suggest a redox state-linked function of SAP12 in plant cells particularly under cold and salt stress.