Auranofin inactivates purified recombinant Trichomonas vaginalis TrxR. (A) Recombinant TrxR (TVAG_474980) and Trx (TVAG_125500) were expressed in Escherichia coli, purified and analysed by polyacrylamide gel electrophoresis (PAGE) and Coomassie straining. Lane M, markers; lane 1, flow through; lane 2, first wash; lane 3, second wash; lanes 4–9, elution fractions. (B,D) TrxR activity was tested in a cell-free system using final concentrations of 80 nM TrxR and 640 nM Trx, and 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB) and NADPH as substrates. Auranofin (AF) and the organic gold(I) compounds 7 and 31 [21], whose structures are shown in (C), were tested at the indicated concentrations. Data (mean ± standard error of the mean; n = 3–8) are expressed as percentage of activity in solvent controls. * P < 0.05 (t-test) vs. controls without test compounds.