Figure 1.

TrxA-dependent growth of STXA2 mutant. WT and STXA2 strains were grown in BG11C containing arsenite (1 mM) and transferred to medium with or without inducer. A, Photographs and (B) growth curve of WT and STXA2 strains in the presence or the absence of inducer at different times. C, Northern blot of trxA gene before (0 h) and after inducer removal (24–72 h). Total RNA was isolated from WT and STXA2 cells at different times. Five micrograms were analyzed and gel was blotted and hybridized with trxA probe. The filter was stripped and rehybridized with an rnpB probe as a loading control. D, Quantification of the relative mRNA levels of trxA in the STXA2 strain relative to the WT. Radioactive signals were quantified and normalized to the rnpB signal using ImageJ software. E, Western blot analysis of TrxA in the WT and STXA2 strains before (0 h) and after inducer removal (24–72 h). From the same cultures used for Northern blot analysis, samples equivalents to 4 ×10⁷ cells were taken at the indicated times, and total proteins were isolated and resolved on SDS–PAGE, blotted, and incubated with anti-TrxA antibody. Different dilutions of total protein extracts from WT cells were loaded (50%, 25%, and 5%) to calculate TrxA protein levels in the STXA2 strain. F, Quantification of TrxA protein levels in the STXA2 strain relative to the WT from results of (E) using ImageJ software. Data are means ± sd from three biological replicates in all cases. ***P < 0.001 (two-tailed Student’s t test between WT and STXA2 strains).