Biosynthesis of the Antitumor Chromomycin A3 in Streptomyces griseus

Abstract

The biosynthetic gene cluster of the aureolic acid type antitumor drug chromomycin A3 from S. griseus subsp. griseus has been identified and characterized. It spans 43 kb and contains 36 genes involved in polyketide biosynthesis and modification, deoxysugar biosynthesis and sugar transfer, pathway regulation and resistance. The organization of the cluster clearly differs from that of the closely related mithramycin. Involvement of the cluster in chromomycin A3 biosynthesis was demonstrated by disrupting the cmmWI gene encoding a polyketide reductase involved in side chain reduction. Three novel chromomycin derivatives were obtained, named chromomycin SK, chromomycin SA, and chromomycin SDK, which show antitumor activity and differ with respect to their 3-side chains. A pathway for the biosynthesis of chromomycin A3 and its deoxysugars is proposed.

An ATP-dependent ligase catalyzes the fourth ring cyclization in tetracycline biosynthesis

“…32,33 Indeed, homologs of SsfL2 that were annotated as acyl-CoA ligases are also found in the reported aureolic acid gene clusters, including MtmL from the mithramycin gene cluster, 34 CmmLII from the chromomycin gene cluster 35 and PokL from the polyketomycin gene cluster. 36 (see Supplementary data, Table S3) To test whether a SsfL2 homolog from these clusters could also catalyze the C1eC18 cyclization reaction, we coexpressed the gene encoding MtmL from Streptomyces argillaceus with those encoded in pWJ83c in S. lividans K4-114.…”

A Novel Mithramycin Analogue with High Antitumor Activity and Less Toxicity Generated by Combinatorial Biosynthesis

“…Agar cultures were removed from the plates and were extracted three times with ethyl acetate. 50 The organic extracts were evaporated under vacuum and finally dissolved in 5 ml of a mixture of DMSO and methanol (50:50). The first purification step was done by chromatography in an XTerra PrepRP18 column (19 × 300 mm, Waters) with acetonitrile and 0.05% trifluoroacetic acid (TFA) in water as solvents.…”

Functional Analyses of Oxygenases in Jadomycin Biosynthesis and Identification of JadH as a Bifunctional Oxygenase/Dehydrase

“…For example, MtmOIV, postulated to be a Baeyer-Villiger monooxygenase (22, 23) responsible for the fourth ring cleavage in the aureolic acid polyketide mithramycin, shares 37.3% identity with JadF and 38.5% identity with JadH. The oxygenase CmmOIV (39.0% identity with JadF and 37.5% with JadH) is suggested to function like MtmOIV in the gene cluster for biosynthesis of the aureolic acid polyketide chromomycin (24), and the oxygenase GrhO6 (35.3% identical to JadF and 36.4% to JadH) is postulated to catalyze ring cleavage in the rubromycin-like polyketide, griseorhodin (25). Three motifs conserved in FAD-and NAD(P)H-dependent monooxygenases are found in JadF and JadH: a dinucleotide binding motif characterized by a Rossmann fold (GxGxxG/A) interacting with the adenosine of FAD (26,27), a GD motif responsible for binding the FAD flavin moiety (28) and a DG motif involved in both FAD and NAD(P)H binding ( Fig.…”