Backbone resonance assignments of the Escherichia coli 62 kDa protein, Hsp31

NMR mapping of the highly flexible regions of 13C/15N-labeled antibody TTAC-0001-Fab

Monoclonal antibody (mAb) drugs are clinically important for the treatment of various diseases. TTAC-0001 is under development as a new anti-cancer antibody drug targeting VEGFR-2. As the less severe toxicity of TTAC-0001 compared to Bevacizumab, likely due to the decreased in vivo half-life, seems to be related to its structural flexibility, it is important to map the exact flexible regions. Although the ¹³C/¹⁵N-labeled protein is required for NMR analyses, it is difficult to obtain antibody fragments (Fab and scFv) containing disulfide bonds through general cytosolic expression in Escherichia coli (E. coli). Here, we notably increased the periplasmic expression of the ¹³C/¹⁵N-labeled TTAC-0001-Fab (¹³C/¹⁵N-TTAC-Fab) through simple isopropyl β-D-1-thiogalactopyranoside (IPTG)-induction at an increased optical density (1.5 OD_600nm). Through NMR triple resonance experiments, two loop insertions (LI-1 between the V_H and C_H1; LI-2 between the V_L and C_L) were confirmed to be highly flexible. The additional LIs could be another way to engineer the antibody by changing the pharmacokinetic properties.

Zinc-mediated Reversible Multimerization of Hsp31 Enhances the Activity of Holding Chaperone

Hsp31 protein, belonging to the DJ-1/ThiJ/PfpI 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 (HMW_Zinc), resulting in an enhanced chaperone activity. Furthermore, it was shown that the formation of HMW_Zinc 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 HMW_Zinc 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 β-to-α region. A treatment with hydrogen peroxide accelerated HMW_Zinc formation, so that the Hsp31^C185E mutant rendered the formation of HMW_Zinc even at 45 °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 HMW_Zinc occurs in the presence of heat and Zn⁺² ion.