Chaperone activity with a redox switch

Article Abstract:

A study of the regulatory function of the Hsp33, a heat shock protein that was found to be a very potent molecular chaperone, revealed that Hsp33 becomes an active folding helper protein in an oxidizing environment, protecting cells from oxidants. Results also showed that oxidizing conditions lead to the formation of disulfide bonds in Hsp33 that serve as a molecular switch for activating its chaperone function. These findings suggest that Hsp33 plays an important role in defending against bacteria during oxidative stress.

Heat shock proteins

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Oxidative protein folding is driven by the electron transport system

Article Abstract:

An enzymatic assay for diosulfide bond B (DsbB) was created to characterize the DsbA-DsbB system in a biochemical manner. It was shown that catalysis of reduced DsbA's oxidation in vitro is undertaken by membranes containing overexpressed DsbB. The assay also reveals that the activity of DsbB is highly dependent on the existence of oxygen, which suggests that oxygen can act as the final electron acceptor. The importance of the components of the electron transport system in the reoxidation of DsbB was also established.

Analysis, Protein folding, Electron transport

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Why is DsbA such an oxidizing disulfide catalyst?

Article Abstract:

The high oxidizing ability of the DsbA protein, an oxidoreductase, is due to the instability of the active site disulfide and low pK(sub a) of the Cys-30 residue. DsbA oxidizes newly formed proteins by transferring its disulfide group to them. The stability of the reduced form of DsbA is more than that of the oxidized form. The low pK(sub a) of Cys-30 makes DsbA negatively charged at neutral pH which lets the protein exit the oxidizing reaction in the reduced form.

Enzymes, Enzyme structure-activity relationships

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