title: The granaticin biosynthetic gene cluster of Streptomyces violaceoruber Tü22: sequence analysis and expression in a heterologous host.
abstract: BACKGROUND
  The granaticins are members of the benzoisochromanequinone class of aromatic polyketides, the best known member of which is actinorhodin made by Streptomyces coelicolor A3(2). Genetic analysis of this class of compounds has played a major role in the development of hypotheses about the way in which aromatic polyketide synthases (PKSs) control product structure. Although the granaticin nascent polyketide is identical to that of actinorhodin, post-PKS steps involve different pyran-ring stereochemistry and glycosylation. Comparison of the complete gene clusters for the two metabolites is therefore of great interest.
  
  
  RESULTS
  The entire granaticin gene cluster (the gra cluster) from Streptomyces violaceoruber T-22 was cloned on either of two overlapping cosmids and expressed in the heterologous host, Streptomyces coelicolor A3(2), strain CH999. Chemical analysis of the recombinant strains demonstrated production of granaticin, granaticin B, dihydrogranaticin and dihydrogranaticin B, which are the four known metabolites of S. violaceoruber. Analysis of the complete 39,250 base pair sequence of the insert of one of the cosmids, pOJ466-22-24, revealed 37 complete open reading frames (ORFs), 15 of which resemble ORFs from the act (actinorhodin) gene cluster of S. coelicolor A3(2). Among the rest, nine resemble ORFs potentially involved in deoxysugar metabolism from Streptomyces spp. and other bacteria, and six resemble regulatory ORFs.
  
  
  CONCLUSIONS
  On the basis of these resemblances, putative functional assignments of the products of most of the newly discovered ORFs were made, including those of genes involved in the PKS and tailoring steps in the biosynthesis of the granaticin aglycone, steps in the deoxy sugar pathway, and putative regulatory and export functions.
authors.affiliation: Department of Genetics John Innes Centre Norwich Research Park Colney Norwich NR4 7UH UK.
authors.forename: K
authors.initials: K
authors.lastname: Ichinose
authors.forename: D J
authors.initials: DJ
authors.lastname: Bedford
authors.forename: D
authors.initials: D
authors.lastname: Tornus
authors.forename: A
authors.initials: A
authors.lastname: Bechthold
authors.forename: M J
authors.initials: MJ
authors.lastname: Bibb
authors.forename: W P
authors.initials: WP
authors.lastname: Revill
authors.forename: H G
authors.initials: HG
authors.lastname: Floss
authors.forename: D A
authors.initials: DA
authors.lastname: Hopwood
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D003360:Cosmids; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D006031:Glycosylation; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000096:biosynthesis / Q000235:genetics; D005810:Multigene Family / Q000235:genetics*; D009285:Naphthoquinones / Q000302:isolation & purification / Q000378:metabolism; D016366:Open Reading Frames; D010957:Plasmids; D012343:RNA, Transfer / Q000096:biosynthesis / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism*; D000095622:Benzoisochromanequinones
chemical_list: D004269:DNA, Bacterial; D009097:Multienzyme Complexes; D009285:Naphthoquinones; D012343:RNA, Transfer; D011994:Recombinant Proteins; C091616:daunorubicin-doxorubicin polyketide synthase; C009811:granaticin; D000095622:Benzoisochromanequinones