The crystal structure of manganese peroxidase from Phanerochaete chrysosporium at 2.06-A resolution

The crystal structure of manganese peroxidase (MnP) from the lignin-degrading basidiomycetous fungus Phanerochaete chrysosporium has been solved using molecular replacement techniques and refined to R = 0.20 at 2.0 A. The overall structure is similar to that of two other fungal peroxidases, lignin peroxidase from P. chrysosporium and Arthromyces ramosus peroxidase. Like the other fungal peroxidases, MnP has two structural calcium ions. MnP also has two N-acetylglucosamine residues N-linked to Asn131 that are readily visible in the electron density map. The active site, consisting of a proximal His ligand H-bonded to an Asp residue and a distal side peroxide binding pocket consisting of a catalytic His and Arg, is the same as in the aforementioned fungal peroxidases as well as yeast cytochrome c peroxidase. MnP differs in having five rather than four disulfide bonds. The additional disulfide bond, Cys341-Cys348, is located near the C terminus of the polypeptide chain. Importantly, a new cation binding site, which we propose is the manganese-binding site of MnP, was located in the crystal structure. The ligands constituting the Mn(2+)-binding site include Asp179, Glu35, Glu39, a heme propionate, and two water molecules. Electron transfer from Mn2+ to the heme edge or iron center is envisioned to occur through a sigma-bonded pathway along a heme propionate.