Extreme acidophilic bacteria like sp. require an efficient enzyme system to counteract strong oxygen stress conditions in their natural habitat. The genome of sp. CF-1 encodes the thioredoxin-fold protein TFP2, which exhibits a high structural similarity to the thioredoxin domain of CnoX. CnoX from is a chaperedoxin that protects protein substrates from oxidative stress conditions using its holdase function and a subsequent transfer to foldase chaperones for refolding. Recombinantly produced and purified sp. TFP2 possesses both thioredoxin and chaperone holdase activities in vitro. It can be reduced by thioredoxin reductase (TrxR). The gene co-locates with genes for the chaperone foldase GroES/EL on the chromosome. The " cluster" () was found between 1.9 and 8.8-fold transcriptionally up-regulated in response to 1 mM hydrogen peroxide (HO). sp. heterologously expressed in wild type and mutant strains lead to an increased tolerance of these strains to HO and significantly reduced intracellular protein aggregates. Finally, a proteomic analysis of protein aggregates produced in upon exposition to oxidative stress with 4 mM HO, showed that sp. expression caused a significant decrease in the aggregation of 124 proteins belonging to fifteen different metabolic categories. These included several known substrates of DnaK and GroEL/ES. These findings demonstrate that sp. TFP2 is a chaperedoxin-like protein, acting as a key player in the control of cellular proteostasis under highly oxidative conditions that prevail in extreme acidic environments.