FIG 6.

ArsR2 negatively regulates the expression of arsK. (A) RT-PCR analysis illustrating the cotranscription of arsR2 and arsK. Total RNA was extracted from strain GW4 grown in MMNH₄ medium with 1 mM As(III). M, molecular weight marker (DL 2000 plus). In lanes 1 and 4, total DNA was used as the template; in lanes 2 and 5, total RNA was used as the template; in lines 3 and 6, double-distilled water (ddH₂O) was used as the template. The horizontal lines represent the locations of primers. (B) EMSAs. FAM-labeled arsR2-arsK probe interacted with ArsR2 protein. The amounts of DNA probes and ArsR2 are shown in the tables above each panel. Competition EMSAs including arsR2-arsK probe and ArsR2 protein with increasing amounts of As(III) (C), Sb(III) (D), Rox(III) (E), MAs(III) (F), As(V) (G), or dimethyl-As(III) (H). The amount of DNA probe was 100 ng, the amount of ArsR2 was 1.0 μM, and the amounts of each metalloid are shown in the tables above each panel.