Crystal structures of two novel dye-decolorizing peroxidases reveal a β-barrel fold with a conserved heme-binding motif

BtDyP from Bacteroides thetaiotaomicron (strain VPI‐5482) and TyrA from Shewanella oneidensis are dye‐decolorizing peroxidases (DyPs), members of a new family of heme‐dependent peroxidases recently identified in fungi and bacteria. Here, we report the crystal structures of BtDyP and TyrA at 1.6 and 2.7 Å, respectively. BtDyP assembles into a hexamer, while TyrA assembles into a dimer; the dimerization interface is conserved between the two proteins. Each monomer exhibits a two‐domain, α+β ferredoxin‐like fold. A site for heme binding was identified computationally, and modeling of a heme into the proposed active site allowed for identification of residues likely to be functionally important. Structural and sequence comparisons with other DyPs demonstrate a conservation of putative heme‐binding residues, including an absolutely conserved histidine. Isothermal titration calorimetry experiments confirm heme binding, but with a stoichiometry of 0.3:1 (heme:protein). Proteins 2007. © 2007 Wiley‐Liss, Inc.