The highly conserved DnaK-DnaJ-GrpE system protects cells against elevated temperatures. Under oxidative heat stress conditions, however, DnaK reversibly looses its chaperone activity. This is caused by a dramatic degrease of the cellular ATP concentration due to oxidative stress. Now, the ATP-independent, redox-regulated chaperone holdase Hsp33 binds to aggregation sensitive proteins until non-stress conditions are restored. Then, DnaK reactivates and supports the refolding of Hsp33-bound substrate proteins. Studies with the co-chaperone DnaJ show an independent function for DnaJs two highly conserved zinc centers. While zinc center I is important for DnaJs autonomous, DnaK-independent chaperone activity, zinc center II is essential for the catalytic activity of the DnaK-DnaJ-GrpE machine. In addition to the J-domain of DnaJ, DnaK needs to interact with zinc center II in order to reach high affinity for substrate proteins.
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The highly conserved DnaK-DnaJ-GrpE system protects cells against elevated temperatures. Under oxidative heat stress conditions, however, DnaK reversibly looses its chaperone activity. This is caused by a dramatic degrease of the cellular ATP concentration due to oxidative stress. Now, the ATP-independent, redox-regulated chaperone holdase Hsp33 binds to aggregation sensitive proteins until non-stress conditions are restored. Then, DnaK reactivates and supports the refolding of Hsp33-bound subst...
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