CLONING OF THE RIB7 GENE ENCODING THE RIB OFLAVIN SYNTHASE OF THE YEAST PICHIA-GUILLIERMONDII

The RIB7 gene encoding the enzyme of the final stage of riboflavin bio synthesis in Pichia guilliermondii - riboflavin synthase was cloned on the pFL38 shuttle vector as the Sau3A fragment of the chromosomal DNA of about 4 kb. The HindIII fragment of 1.4 kb was subcloned from the hybrid plasmid pFR7 obtained onto the pUC18 plasmid. The plasmid pR7 t hus constructed transform Escherichia coli ribB-45 mutant cells with a blocked riboflavin synthase approximately at the same frequency as pF R7. High riboflavin synthase activity was discovered in the E. coli tr ansformants carrying pR7 but not pFR7. Using both plasmids we also com plemented rib17 mutant of P. guilliermondii.