title: First crystal structure of a fungal high-redox potential dye-decolorizing peroxidase: substrate interaction sites and long-range electron transfer.
abstract: Dye-decolorizing peroxidases (DyPs) belong to the large group of heme peroxidases. They utilize hydrogen peroxide to catalyze oxidations of various organic compounds. AauDyPI from Auricularia auricula-judae (fungi) was crystallized, and its crystal structure was determined at 2.1 Å resolution. The mostly helical structure also shows a β-sheet motif typical for DyPs and Cld (chlorite dismutase)-related structures and includes the complete polypeptide chain. At the distal side of the heme molecule, a flexible aspartate residue (Asp-168) plays a key role in catalysis. It guides incoming hydrogen peroxide toward the heme iron and mediates proton rearrangement in the process of Compound I formation. Afterward, its side chain changes its conformation, now pointing toward the protein backbone. We propose an extended functionality of Asp-168, which acts like a gatekeeper by altering the width of the heme cavity access channel. Chemical modifications of potentially redox-active amino acids show that a tyrosine is involved in substrate interaction. Using spin-trapping experiments, a transient radical on the surface-exposed Tyr-337 was identified as the oxidation site for bulky substrates. A possible long-range electron transfer pathway from the surface of the enzyme to the redox cofactor (heme) is discussed.
authors.affiliation: Institute of Organic Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany.
authors.forename: Eric
authors.initials: E
authors.lastname: Strittmatter
authors.forename: Christiane
authors.initials: C
authors.lastname: Liers
authors.forename: René
authors.initials: R
authors.lastname: Ullrich
authors.forename: Sabrina
authors.initials: S
authors.lastname: Wachter
authors.forename: Martin
authors.initials: M
authors.lastname: Hofrichter
authors.forename: Dietmar A
authors.initials: DA
authors.lastname: Plattner
authors.forename: Klaus
authors.initials: K
authors.lastname: Piontek
mesh_terms: D020816:Amino Acid Motifs; D001487:Basidiomycota / Q000201:enzymology*; D018360:Crystallography, X-Ray; D004579:Electron Transport; D005656:Fungal Proteins / Q000737:chemistry*; D006418:Heme / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D009195:Peroxidase / Q000737:chemistry*; D017434:Protein Structure, Tertiary
chemical_list: D005656:Fungal Proteins; D006418:Heme; D006861:Hydrogen Peroxide; D007501:Iron; D009195:Peroxidase