title: Amino acid precursor supply in the biosynthesis of the RNA polymerase inhibitor streptolydigin by Streptomyces lydicus.
abstract: Biosynthesis of the hybrid polyketide-nonribosomal peptide antibiotic streptolydigin, 3-methylaspartate, is utilized as precursor of the tetramic acid moiety. The three genes from the Streptomyces lydicus streptolydigin gene cluster slgE1-slgE2-slgE3 are involved in 3-methylaspartate supply. SlgE3, a ferredoxin-dependent glutamate synthase, is responsible for the biosynthesis of glutamate from glutamine and 2-oxoglutarate. In addition to slgE3, housekeeping NADPH- and ferredoxin-dependent glutamate synthase genes have been identified in S. lydicus. The expression of slgE3 is increased up to 9-fold at the onset of streptolydigin biosynthesis and later decreases to ∼2-fold over the basal level. In contrast, the expression of housekeeping glutamate synthases decreases when streptolydigin begins to be synthesized. SlgE1 and SlgE2 are the two subunits of a glutamate mutase that would convert glutamate into 3-methylaspartate. Deletion of slgE1-slgE2 led to the production of two compounds containing a lateral side chain derived from glutamate instead of 3-methylaspartate. Expression of this glutamate mutase also reaches a peak increase of up to 5.5-fold coinciding with the onset of antibiotic production. Overexpression of either slgE3 or slgE1-slgE2 in S. lydicus led to an increase in the yield of streptolydigin.
authors.affiliation: Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Gómez
authors.forename: Dina H
authors.initials: DH
authors.lastname: Horna
authors.forename: Carlos
authors.initials: C
authors.lastname: Olano
authors.forename: Martina
authors.initials: M
authors.lastname: Palomino-Schätzlein
authors.forename: Antonio
authors.initials: A
authors.lastname: Pineda-Lucena
authors.forename: Rodrigo J
authors.initials: RJ
authors.lastname: Carbajo
authors.forename: Alfredo F
authors.initials: AF
authors.lastname: Braña
authors.forename: Carmen
authors.initials: C
authors.lastname: Méndez
authors.forename: José A
authors.initials: JA
authors.lastname: Salas
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism / Q000494:pharmacology*; D000617:Aminoglycosides / Q000096:biosynthesis* / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D008969:Molecular Sequence Data; D058990:Molecular Targeted Therapy; D016254:Mutagenesis, Insertional; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013302:Streptomyces / Q000235:genetics / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D012313:RNA; C100307:streptolydigin; D012321:DNA-Directed RNA Polymerases