Riboflavin Biosynthesis in Saccharomyces cerevisiae CLONING, CHARACTERIZATION, AND EXPRESSION OF THE RIB5 GENE ENCODING RIBOFLAVIN SYNTHASE

摘要: Saccharomyces cerevisiae has a monofunctional riboflavin synthase that catalyzes the formation of from 6,7-dimethyl-8-ribityllumazine. We have isolated gene encoding this enzyme yeast genomic library by functional complementation mutant, rib5-10, lacking activity. Deletion chromosomal copy RIB5 led to auxotrophy and loss Intragenic between point deletion mutant alleles suggested encoded protein (Rib5p) assembles into multimeric complex predicted existence discrete domain located at N terminus. Nucleotide sequencing revealed 714-base pair open reading frame 25-kDa protein. Rib5p was purified apparent homogeneity simple procedure. The specific activity enriched 8500-fold. N-terminal sequence identical nucleotide gene. Initial structural characterization gel filtration chromatography both nondenaturing pore limit SDS-polyacrylamide electrophoresis showed forms trimer subunits. derived amino acid shows extensive homology sequences α subunits Bacillus subtilis other prokaryotes. In addition, also internal C-terminal halves Taken together, these results suggest subunit contains two structurally related (substrate-binding) but catalytically different (acceptor donator) domains.