CLONING OF A TYROSINASE GENE IN STREPTOCOCCUS-THERMOPHILUS

The streptococcal cloning vector pIL253 (4.96-kbp, Em(r)) was used to introduce the Streptomyces antibioticus tyrosinase (mel) gene (1.56-kb p) into S. thermophilus, an important microbe in dairy fermentations. Electrotransformants of S. thermophilus ST128 contained 6.51-kbp recom binant plasmids which probed positively in Southern hybridizations wit h the biotin-labeled mel fragment. Western blots of cell extracts reso lved by SDS-PAGE showed the presence of a ca. 31-kDa band thus confirm ing the synthesis of tyrosinase protein by genetic transformants.