title: Occurrence of a putative ancient-like isomerase involved in histidine and tryptophan biosynthesis.
abstract: We report the occurrence of an isomerase with a putative (betaalpha)(8)-barrel structure involved in both histidine and trypto-phan biosynthesis in Streptomyces coelicolor A3(2) and Mycobacterium tuberculosis HR37Rv. Deletion of a hisA homologue (SCO2050) putatively encoding N'-[(5'-phosphoribosyl)-formimino]-5 amino-imidazole-4-carboxamide ribonucleotide isomerase from the chromosome of S. coelicolor A3(2) generated a double auxotrophic mutant for histidine and tryptophan. The bifunctional gene SCO2050 and its orthologue Rv1603 from M. tuberculosis complemented both hisA and trpF mutants of Escherichia coli. Expression of the E. coli trpF gene in the S. coelicolor mutant only complemented the tryptophan auxo-trophy, and the hisA gene only complemented the histidine auxotrophy. The discovery of this enzyme, which has a broad-substrate specificity, has implications for the evolution of metabolic pathways and may prove to be important for understanding the evolution of the (betaalpha)(8)-barrels.
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK. fbarona-gomez@bio.warwick.ac.uk
authors.forename: Francisco
authors.initials: F
authors.lastname: Barona-Gómez
authors.forename: David A
authors.initials: DA
authors.lastname: Hodgson
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D016384:Consensus Sequence; D017931:DNA Primers; D017353:Gene Deletion; D005816:Genetic Complementation Test; D005838:Genotype; D006639:Histidine / Q000096:biosynthesis*; D007535:Isomerases / Q000235:genetics*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013302:Streptomyces / Q000201:enzymology* / Q000235:genetics; D014364:Tryptophan / Q000096:biosynthesis*
chemical_list: D017931:DNA Primers; D006639:Histidine; D014364:Tryptophan; D007535:Isomerases; D019747:Aldose-Ketose Isomerases; C079656:Phosphoribosyl-5-amino-1-phosphoribosyl-4-imidazolecarboxiamide isomerase; C029865:phosphoribosylanthranilate isomerase