title: Sequence analysis of porothramycin biosynthetic gene cluster.
abstract: The biosynthetic gene cluster of porothramycin, a sequence-selective DNA alkylating compound, was identified in the genome of producing strain Streptomyces albus subsp. albus (ATCC 39897) and sequentially characterized. A 39.7 kb long DNA region contains 27 putative genes, 18 of them revealing high similarity with homologous genes from biosynthetic gene cluster of closely related pyrrolobenzodiazepine (PBD) compound anthramycin. However, considering the structures of both compounds, the number of differences in the gene composition of compared biosynthetic gene clusters was unexpectedly high, indicating participation of alternative enzymes in biosynthesis of both porothramycin precursors, anthranilate, and branched L-proline derivative. Based on the sequence analysis of putative NRPS modules Por20 and Por21, we suppose that in porothramycin biosynthesis, the methylation of anthranilate unit occurs prior to the condensation reaction, while modifications of branched proline derivative, oxidation, and dimethylation of the side chain occur on already condensed PBD core. Corresponding two specific methyltransferase encoding genes por26 and por25 were identified in the porothramycin gene cluster. Surprisingly, also methyltransferase gene por18 homologous to orf19 from anthramycin biosynthesis was detected in porothramycin gene cluster even though the appropriate biosynthetic step is missing, as suggested by ultra high-performance liquid chromatography-diode array detection-mass spectrometry (UHPLC-DAD-MS) analysis of the product in the S. albus culture broth.
authors.affiliation: Institute of Microbiology AS CR, Videnska 1083, 142 20, Prague 4, Czech Republic, lucie.najmanova@biomed.cas.cz.
authors.forename: Lucie
authors.initials: L
authors.lastname: Najmanova
authors.forename: Dana
authors.initials: D
authors.lastname: Ulanova
authors.forename: Marketa
authors.initials: M
authors.lastname: Jelinkova
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Kamenik
authors.forename: Eliska
authors.initials: E
authors.lastname: Kettnerova
authors.forename: Marketa
authors.initials: M
authors.lastname: Koberska
authors.forename: Radek
authors.initials: R
authors.lastname: Gazak
authors.forename: Bojana
authors.initials: B
authors.lastname: Radojevic
authors.forename: Jiri
authors.initials: J
authors.lastname: Janata
mesh_terms: D000876:Anthramycin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D005810:Multigene Family; D017421:Sequence Analysis; D013302:Streptomyces / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D000876:Anthramycin; C057882:porothramycin A