A near atomic resolution structure of a Melanocarpus albomyces laccase.

We have solved a crystal structure from Melanocarpus albomyces laccase expressed in the filamentous fungus Trichoderma reesei (rMaL) at 1.3A resolution by using synchrotron radiation at 100K. At the moment, this is the highest resolution that has been attained for any multicopper oxidase. The present structure confirmed our earlier proposal regarding the dynamic behaviour of the copper cluster. Thermal ellipsoids of copper atoms indicated movements of trinuclear site coppers. The direction of the type-3 copper motion was perpendicular to the type-2 copper. In addition, the structure at 1.3A resolution allowed us to describe important solvent cavities of the enzyme and the structure is also compared with other known multicopper oxidases. T2 and T3 solvent cavities, and a putative SDS-gate, formed by Ser142, Ser510 and the C-terminal Asp556 of rMaL, are described. We also observed a 2-oxohistidine, an oxidized histidine, possibly caused by a metal-catalysed oxidation by the trinuclear site coppers. To our knowledge, this is the first time that 2-oxohistidine has been observed in a protein crystal structure.