Nucleotide sequence of Saccharomyces cerevisiae genes TRP2 and TRP3 encoding bifunctional anthranilate synthase: indole-3-glycerol phosphate synthase.

Saccharomyces cerevisiaeanthranilate synthase:indole-3-glycerol phosphate synthase is a multifunctional hetero-oligomeric enzyme encoded by genes TRPB and TRP3.TRP2, encoding anthranilate synthase Component I, was cloned by complementation of a yeast trp2 mutant.The nucleotide sequence of TRP2 as well as that of TRP3 were determined.The deduced anthranilate synthase Component I primary structure from yeast exhibits only limited similarity to that of the corresponding Escherichia coli subunit encoded by trpE.On the other hand, yeast anthranilate synthase Component I1 and indole-3-glycerol phosphate synthase amino acid sequences from TRP3 are clearly homologous with the corresponding sequences of the E. coli trpG and trpC polypeptide segments and thereby establish the bifunctional structure of TRP3 protein.Based on comparisons of TRPS amino acid sequence with homologous sequences from E. coli and Neurospora crassa, an 11-amino acid residue connnecting segment was identified which fuses the trpG and trpC functions of the bifunctional TRP3 protein chain.These comparisons support the conclusion that the amino acid sequence of connectors in homologous multifunctional enzymes need not be conserved.Connector function is thus not dependent on a specific sequence.Nuclease S1 mapping was used to identify mRNA 5' termini.Heterogeneous 5' termini were found for both TRP2 and TRPS mRNA.TRP2 and TRP3 5"flanking regions were analyzed for sequences that might function in regulation of these genes by the S. cerevisiae general amino acid control system.The 9 base pair direct repeat (Hinnebusch, A. G., and Fink, G .R. (