Hsp31 protein, belonging to the DJ-1/ThiJ/Pfpl superfamily, increases the survival of Escherichia coli under various stresses. While it was reported as a holding chaperone, Hsp31 was also shown to exhibit the glyoxalase III activity in subsequent study. Here, we describe our finding that Hsp31 undergoes a Zn+2-mediated multimerization (HMWzinc), resulting in an enhanced chaperone activity. Furthermore, it was shown that the formation of HMWzinc is reversible such that the oligomer dissociates into the native dimer by EDTA incubation. We attempted to determine the structural change involving the transition between the native dimer and HMWzinc by adding Ni+2, which is Zn+2-mimetic, producing a potential intermediate structure. An analysis of this intermediate revealed a structure with hydrophobic interior exposed, due to an unfolding of the N-terminal loop and the C-terminal beta-to-alpha region. A treatment with hydrogen peroxide accelerated HMWzinc formation, so that the Hsp31(C185E) mutant rendered the formation of HMWzinc even at 45 degrees C. However, the presence of Zn+2 in the catalytic site antagonizes the oxidation of C185, implying a negative role. Our results suggest an unprecedented mechanism of the enhancing chaperone activity by Hsp31, in which the reversible formation of HMWzinc occurs in the presence of heat and Zn+2 ion. (C) 2018 Elsevier Ltd. All rights reserved.