Crystal structure and biochemical features of dye-decolorizing peroxidase YfeX from Escherichia coli O157 Asp{sup 143} and Arg{sup 232} play divergent roles toward different substrates

YfeX from Escherichia coli O157 is a bacterial dye-decolorizing peroxidase that represents both dye-decoloring activity and typical peroxidase activity. We reported the crystal structure of YfeX bound to heme at 2.09 Å resolution. The YfeX monomer resembles a ferredoxin-like fold and contains two domains. The three conserved residues surrounding the heme group are His{sup 215}, Asp{sup 143} and Arg{sup 232}. His{sup 215} functions as the proximal axial ligand of the heme iron atom. Biochemical data show that the catalytic significance of the conserved Asp{sup 143} and Arg{sup 232} depends on the substrate types and that YfeX may adopt various catalytic mechanisms toward divergent substrates. In addition, it is observed that an access tunnel spans from the protein molecular surface to the heme distal region, it serves as the passageway for the entrance and binding of the H{sub 2}O{sub 2}. - Highlights: • We determined the crystal structure of YfeX bound to heme at 2.09 Å resolution. • The conserved Asp{sup 143} and Arg{sup 232} play different roles toward divergent substrates. • The H{sub 2}O{sub 2} access tunnel spans from the protein molecular surface to the heme distal region.