Crystallization and preliminary structure analysis of the blue laccase from the ligninolytic fungus Panus tigrinus

The blue laccase from the white-rot basidiomycete fungus Panus tigrinus, an enzyme involved in lignin biodegradation, has been crystallized. P. tigrinus laccase crystals grew within one week at 296 K using the sitting-drop vapour-diffusion method in 22%(w/v) PEG 4000, 0.2 M CaCl₂, 100 mM Tris–HCl pH 7.5. The crystals belong to the monoclinic space group P2₁, with unit-cell parameters a = 54.2, b = 111.6, c = 97.1, β = 97.7°, and contain 46% solvent. A complete native data set was collected to 1.4 Å resolution at the copper edge. Molecular replacement using the Coprinus cinereus laccase structure (PDB code 1hfu) as a starting model was performed and initial electron-density maps revealed the presence of a full complement of copper ions. Model refinement is in progress. The P. tigrinus laccase structural model exhibits the highest resolution available to date and will assist in further elucidation of the catalytic mechanism and electron-transfer processes for this class of enzymes.