Figure 10.

Determination of the molecular mass of diamide or arsenite treated ArsR1. First, 0.5 mL of sample (1.0 mg mL⁻¹ of proteins) was loaded onto a Superose 12 10/300 GL (GE Healthcare) analytical and preparative column equilibrated by 10 mM MOPS/0.1 M NaCl/15% glycerol (pH 7.5). The flow rate after sample application was 0.5 mL min⁻¹. Marker proteins (solid squares in inset graph) were albumin (66.7 kDa), ovalbumin (43 kDa), chymotrypsinogen A (25.7 kDa) and ribonuclease A (13.7 kDa). Line a, ArsR1 alone; line b, ArsR1 in the presence of 1 mM diamide; line c, ArsR1 in the presence of 0.1 mM arsenite. Molecular masses calculated from the calibration curve were 33.1 kDa (a), 16.8 kDa (b) and 16.6 kDa (c). The theoretical molecular mass of the His-tagged monomer is 16,744 Da.