The Arabidopsis KS-type dehydrin recovers lactate dehydrogenase activity inhibited by copper with the contribution of His residues

• Dehydrin is a group 2 late embryogenesis abundant (LEA) proteins which is related to water stress tolerance in plants.
• Here, we found that Arabidopsis dehydrin reactivated the lactate dehydrogenase which had been inactivated by Cu2+.
• This is the first report showing that dehydrin can protect proteins from the heavy metal damage.

Dehydrin, which is one of the late embryogenesis abundant (LEA) proteins, is involved in the ability of plants to tolerate the lack of water. Although many reports have indicated that dehydrins bind heavy metals, the physiological role of this metal binding has not been well understood. Here, we report that the Arabidopsis KS-type dehydrin (AtHIRD11) recovered the lactate dehydrogenase (LDH) activity denatured by Cu2+. The LDH activity was partially inhibited by 0.93 μM Cu2+ but totally inactivated by 9.3 μM Cu2+. AtHIRD11 recovered the activity of LDH treated with 9.3 μM Cu2+ in a dose-dependent manner. The recovery activity of AtHIRD11 was significantly higher than those of serum albumin and lysozyme. The conversion of His residues to Ala in AtHIRD11 resulted in the loss of the Cu2+ binding of the protein as well as the disappearance of the conformational change induced by Cu2+ that is observed by circular dichroism spectroscopy. The mutant protein showed lower recovery activity than the original AtHIRD11. These results indicate that AtHIRD11 can reactivate LDH inhibited by Cu2+ via the His residues. This function may prevent physiological damage to plants due to heavy-metal stress.