[Cloning of the RIB7 gene encoding the riboflavin synthase of the yeast Pichia guilliermondii].

The RIB7 gene encoding the enzyme of the final stage of riboflavin biosynthesis 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 thus constructed transform Escherichia coli ribB-45 mutant cells with a blocked riboflavin synthase approximately at the same frequency as pFR7. High riboflavin synthase activity was discovered in the E. coli transformants carrying pR7 but not pFR7. Using both plasmids we also complemented rib17 mutant of P. guilliermondii.