Regulation of Hsp31 chaperone activity by metal-induced structural change

Abstract

Hsp31 protein belongs to the DJ-1/ThiJ/PfpI superfamily, and increases the survival of Escherichia coli in stressful conditions. It was initially reported as a holding chaperone, and its glyoxalase III activity has recently been characterized. Although Hsp31 becomes a high molecular weight form at $60 ^\circ C$ ($HMW_{Heat}$) that has an enhanced chaperone activity compared to the native dimer, the HMWHeat doesn’t seem to have a biological relevance due to the high temperature. Here, we reported a novel mechanism by which the $Zn^{+2}$ -mediated high molecular weight form ($HMW_{Znic}$) of Hsp31 occurred at $50 ^\circ C$ and acquired an increased chaperone activity. Moreover, the $HMW_{Znic}$ was reversible to the native dimer by EDTA-incubation. The analyses of the chromatographic intermediate between the native dimer and the HMWZnic, which was stabilized by the $Ni^{+2}$ incorporation, revealed that the unfolding of the N-terminal long loop and the C-terminal $\alpha$ -helix led to the exposure of the hydrophobic interior. The $H_2O_2$ -treatment accelerated the $HM_{Znic}$ formation of Hsp31, and the C185E mutant mimicking the Cys oxidation was able to form the $HMW_{Znic}$ even at $45 ^\circ C$. Two distinct characteristics of the $HMW_{Znic}$ formation (the reversibility and the need for a low $Zn^{+2}$ concentration) shed a clue on the regulatory mechanism of Hsp31 via the structural change for the glyoxalase III and chaperone activities.