Glycosylated yellow laccases of the basidiomycete Stropharia aeruginosa

• S. aeruginosa secretes glycosylated yellow laccases Yel1p and Yel3p.
• Yel1p and Yel3p have been purified and characterised.
• Low coverage, high throughput transcriptome sequencing identified the Yel1 gene.
• Theories about the differences between yellow and blue laccases are discussed.

Here we describe the identification, purification and characterisation of glycosylated yellow laccase proteins from the basidiomycete fungus Stropharia aeruginosa. Biochemical characterisation of two yellow laccases, Yel1p and Yel3p, show that they are both secreted, monomeric, N-glycosylated proteins of molecular weight around 55 kDa with substrate specificities typical of laccases, but lacking the absorption band at 612 nm typical of the blue laccase proteins. Low coverage, high throughput 454 transcriptome sequencing in combination with inverse-PCR was used to identify cDNA sequences. One of the cDNA sequences has been assigned to the Yel1p protein on the basis of identity between the translated protein sequence and the peptide data from the purified protein, and the full length gene sequence has been obtained. Biochemical properties, substrate specificities and protein sequence data have been used to discuss the unusual spectroscopic properties of S. aeruginosa proteins in the context of recent theories about the differences between yellow and blue laccases.