Redox-regulated chaperone function and conformational changes of Escherichia coli Hsp33

We have studied the chaperone activity and conformation of Escherichia coli heat shock protein (Hsp)33, whose activity is known to be switched on by o xidative conditions. While oxidized Hsp33 completely prevents the heat-indu ced aggregation of zeta -crystallin at 42 degreesC at a ratio of 1:1 (w/w), the reduced form exhibits only a marginal effect on the aggregation. Far U V-circular dichroism (CD) spectra show that reduced Hsp33 contains a signif icant a-helical component. Oxidation results in significant changes in the far UV-CD spectrum. Near UV-CD spectra show changes in tertiary structural packing upon oxidation. Polarity-sensitive fluorescent probes report enhanc ed hydrophobic surfaces in the oxidized Hsp33. Our studies show that the ox idative activation of the chaperone function of Hsp33 involves observable c onformational changes accompanying increased exposure of hydrophobic pocket s. (C) 2001 Federation of European Biochemical Societies. Published by Else vier Science B.V. All rights reserved.