Figure 6

Molecular models for the nine class-II heme peroxidases (AA2) found in the P. cinnabarinus genome. MnP models (A-C) present a Mn²⁺ oxidation site characteristic of typical MnPs, formed by two glutamates and one aspartate at the internal heme propionate region; LiP models (D-G) exhibit a Trp residue exposed to the solvent, which has been involved in high-redox-potential aromatic compound oxidation by typical LiPs; the VP model (H) obtained for the only peroxidase of this family identified in the genome analysis evidences both the Mn²⁺ oxidation site and the Trp residue exposed to the solvent, characteristic of members of this class-II family; the atypical VP (I) contains an aspartate residue (Asp36) in a position occupied by a glutamate in VPs and MnPs. Two axial histidines, one acting as heme iron ligand (proximal histidine) and the second (distal histidine) contributing to the heme reaction with peroxide, together with an arginine residue characterizing class-II peroxidases are also shown in the nine molecular homology models. Four disulfide bridges are depicted as green sticks. These homology models were obtained at the Swiss-Model protein-homology server [83] using P. eryngii VPL (PDB entries 4FCS, 2VKA and 3FJW) and P. chrysosporium LiPH2 and LiPH8 (PDB entries 1LLP, 1B80 and 1B82) crystal structures as templates.