The nucleotide sequence of the tyrosinase gene from Streptomyces antibioticus and characterization of the gene product.

The sequence of a 1.56-kb DNA fragment containing the tyrosinase gene (mel) from Streptomyces antibioticus was determined and the Mr (30612) and amino acid (aa) sequence of the protein were deduced from the nucleotide (nt) sequence. Intracellular and extracellular tyrosinase from S. antibioticus, transformed with pIJ702 (containing mel), were purified to homogeneity; the Mr (29 500), as determined by Sephadex G-75 chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), was consistent with the value derived from the nt sequence. Edman degradation established that the N-terminal sequence of both the intracellular and extracellular forms of tyrosinase are identical and correspond to the aa sequence derived from the structural gene. In addition, this sequence exhibits striking homology to the N-terminal region of the intracellular and extracellular enzyme purified from Streptomyces glaucescens (Crameri et al., 1982). An additional open reading frame (ORF438) upstream of the mel gene, was also identified that appears to code for a protein (Mr = 14 754) with a putative signal sequence.