Figure 1. HOCl-treated RidA inhibits IlvA.

(a) Untreated RidA (RidA-UT) accelerates α-ketobutyrate generation from threonine catalysed by threonine deaminase IlvA. In the presence of RidA treated with a 10-fold excess of HOCl for 5 min at 37 °C, product formation is clearly decreased below levels of product formation in the absence of RidA indicating inhibition of IlvA. A representative measurement is shown. (b) RidA was incubated with a 10-fold molar excess of diamide, peroxynitrite (ONOO⁻) or HOCl, or a 5-fold molar excess of H₂O₂ or H₂O₂/CuCl₂ for 10 min at 30 °C. Oxidants were removed before analysis of chaperone activity. Relative chaperone activities were calculated by normalizing the change of absorption to HOCl-treated RidA. Diamide, H₂O₂ and peroxynitrite (ONOO⁻) do not induce chaperone activity of RidA. The oligomeric state of RidA without prior treatment (c) or after treatment with a 10-fold excess of HOCl for 5 min at 37 °C (d) was analysed. HOCl was removed with the help of Micro Bio-Spin Chromatography Columns before gel filtration using a Superdex 75 10/300 GL column.