Identification of a possible APS reductase in A. ferrooxidans. Alignment of two different regions of the putative APS reductase (CysH) of A. ferrooxidans (Af) with APS and PAPS reductases from the following organisms: Nitrosomonas europaea (ZP00002617), Allochromatium vinosum (AAF27544), E. coli K12 (P17854), Salmonella typhimurium (P17853), Saccharomyces cerevisiae (P18408). The two APS regions are separated by the / symbol. Conserved amino acids shared by APS and PAPS reductases are shown in red. The four cysteines proposed to coordinate a 4Fe-4S center in APS reductase but not PAPS reductase are identified with asterisks. The conserved APS/PAPS reductase signature (KRT)ECG(LS)H is boxed. Also aligned is part of the putative Plr (PAPS-like reductase) protein predicted from the genome of A. ferrooxidans in which amino acids highlighted in blue are shared with either APS or PAPS reductase and include two of the four critical cysteines of APS reductase (in bold, blue).