Structure and expression of a laccase gene from the ligninolytic basidiomycete Ceriporiopsis subvermispora

Abstract

A gene encoding laccase has been isolated from a genomic library of the white-rot basidiomycete Ceriporiopsis subvermispora constructed in Lambda GEM-ii. This gene (Cs-lcs1) contains an open reading frame of 2215 bp, encoding a mature protein of 499 amino acids with a 21-residue signal peptide. The protein sequence exhibits between 63 and 68% identity with laccases from other basidiomycetes and shares with all of them 10 conserved histidines and one cysteine involved in the coordination of copper atoms at the active site of the enzyme. The gene possesses ii introns, with splicing junctions and internal lariat formation sites adhering to the GT-AG and CTRAY rules, respectively. The upstream region of Cs-lcsl contains a TATA box, two CAAT sites, five putative metal response elements and a ACE1 element. In agreement with the presence of the latter element, transcription of Cs-lcsl is activated by copper and silver, as shown by Northern blot and reverse transcription followed by DNA amplification analyses. Based on Southern blot analysis, Cs-lcsl appears to be the only gene encoding laccase in C. subvermispora.