Multiple sequence alignment of proteins in the aldo–keto reductase (AKR) family. Proteins are represented by their PDB codes: 4ijc, Saccharomyces cerevisiae Ara1 (NP_009707.3); 1mzr, Escherichia coli Dkga (NP_417485.4; Jeudy et al., 2006); 3h7u, Arabidopsis thaliana NADP-linked oxidoreductase (NP_001031505.1; Simpson et al., 2009); 4f4o, Leishmania braziliensis Ara1 (XP_001685202.1; Andersen et al., 2012); 1qwk, Caenorhabditis elegans Ara1 (NP_509242.1; Southeast Collaboratory for Structural Genomics, unpublished work); 1frb, Mus musculus aldose reductase (NP_032038.1; Wilson et al., 1995); 1zua, Homo sapiens Akr1b10 (NP_064695.3; Gallego et al., 2007). The secondary-structure elements of Ara1 (PDB entry 4ijc) are shown at the top. Residues involved in substrate binding are labelled with blue triangles and catalytic residues are marked with red stars. The alignment was performed with ClustalW (Larkin et al., 2007) and ESPript (Gouet et al., 1999).