RESUMEN
Cyclolithistide A is a peptide lactone isolated from marine lithistid sponges. Its entire structure, including absolute configurations, has been reported except the relative and absolute configurations of its characteristic residue, 4-chloroisoleucine (4-CIle). We synthesized four isomers of 4-CIle from furfural-derived N-Boc imine and propionaldehyde. Analysis of the acid hydrolysate of cyclolithistide A and the synthetic samples of 4-CIle after derivatization with l- and d-FDAA permitted us to propose the absolute configuration of the 4-chloroisoleucine residue in cyclolithistide A as 2S,3R,4R.
Asunto(s)
Lactonas , Poríferos , Poríferos/química , Animales , Lactonas/química , Antifúngicos/química , Antifúngicos/farmacología , Estereoisomerismo , Péptidos Cíclicos/química , Conformación Molecular , Estructura MolecularRESUMEN
Two families of DNA glycosylases (YtkR2/AlkD, AlkZ/YcaQ) have been found to remove bulky and crosslinking DNA adducts produced by bacterial natural products. Whether DNA glycosylases eliminate other types of damage formed by structurally diverse antibiotics is unknown. Here, we identify four DNA glycosylases-TxnU2, TxnU4, LldU1 and LldU5-important for biosynthesis of the aromatic polyketide antibiotics trioxacarcin A (TXNA) and LL-D49194 (LLD), and show that the enzymes provide self-resistance to the producing strains by excising the intercalated guanine adducts of TXNA and LLD. These enzymes are highly specific for TXNA/LLD-DNA lesions and have no activity toward other, less stable alkylguanines as previously described for YtkR2/AlkD and AlkZ/YcaQ. Similarly, TXNA-DNA adducts are not excised by other alkylpurine DNA glycosylases. TxnU4 and LldU1 possess unique active site motifs that provide an explanation for their tight substrate specificity. Moreover, we show that abasic (AP) sites generated from TxnU4 excision of intercalated TXNA-DNA adducts are incised by AP endonuclease less efficiently than those formed by 7mG excision. This work characterizes a distinct class of DNA glycosylase acting on intercalated DNA adducts and furthers our understanding of specific DNA repair self-resistance activities within antibiotic producers of structurally diverse, highly functionalized DNA damaging agents.
Asunto(s)
Aductos de ADN , ADN Glicosilasas , Aminoglicósidos , Antibacterianos/farmacología , Daño del ADN , ADN Glicosilasas/metabolismo , Reparación del ADNRESUMEN
BACKGROUND: Streptomyces are well known for their potential to produce various pharmaceutically active compounds, the commercial development of which is often limited by the low productivity and purity of the desired compounds expressed by natural producers. Well-characterized promoters are crucial for driving the expression of target genes and improving the production of metabolites of interest. RESULTS: A strong constitutive promoter, stnYp, was identified in Streptomyces flocculus CGMCC4.1223 and was characterized by its effective activation of silent biosynthetic genes and high efficiency of heterologous gene expression. The promoter stnYp showed the highest activity in model strains of four Streptomyces species compared with the three frequently used constitutive promoters ermEp*, kasOp*, and SP44. The promoter stnYp could efficiently activate the indigoidine biosynthetic gene cluster in S. albus J1074, which is thought to be silent under routine laboratory conditions. Moreover, stnYp was found suitable for heterologous gene expression in different Streptomyces hosts. Compared with the promoters ermEp*, kasOp*, and SP44, stnYp conferred the highest production level of diverse metabolites in various heterologous hosts, including the agricultural-bactericide aureonuclemycin and the antitumor compound YM-216391, with an approximately 1.4 - 11.6-fold enhancement of the yields. Furthermore, the purity of tylosin A was greatly improved by overexpressing rate-limiting genes through stnYp in the industrial strain. Further, the yield of tylosin A was significantly elevated to 10.30 ± 0.12 g/L, approximately 1.7-fold higher than that of the original strain. CONCLUSIONS: The promoter stnYp is a reliable, well-defined promoter with strong activity and broad suitability. The findings of this study can expand promoter diversity, facilitate genetic manipulation, and promote metabolic engineering in multiple Streptomyces species.
Asunto(s)
Productos Biológicos , Streptomyces , Tilosina/metabolismo , Productos Biológicos/metabolismo , Streptomyces/genética , Streptomyces/metabolismo , Regiones Promotoras Genéticas , Familia de MultigenesRESUMEN
Two glycosylated naphthacemycins (naphthacemycins D1 and D2) were identified in Streptomyces sp. N12W1565. These two compounds not only showed antimicrobial potential against bacteria but also exhibited more aqueous solubility than naphthacemycins. Furthermore, the whole genome of Streptomyces sp. N12W1565 has been sequenced, the natY gene, located outside the biosynthetic gene cluster encoding a D-glucose glycosyltransferase, was identified to mediate glycosylation in the phenolic hydroxyl of the naphthacemycin core scaffold. Glycosyltransferase was elucidated in vitro by using a homologous enzyme, which showed potential as a biocatalyst.
Asunto(s)
Streptomyces , Antibacterianos/farmacología , Glicosilación , Glicosiltransferasas/genética , Glicosiltransferasas/metabolismo , Familia de MultigenesRESUMEN
DNA-alkylating natural products play an important role in drug development due to their significant antitumor activities. They usually show high affinity with DNA through different mechanisms with the aid of their unique scaffold and highly active functional groups. Therefore, the biosynthesis of these natural products has been extensively studied, especially the construction of their pharmacophores. Meanwhile, their producing strains have evolved corresponding self-resistance strategies to protect themselves. To further promote the functional characterization of their biosynthetic pathways and lay the foundation for the discovery and rational design of DNA alkylating agents, we summarize herein the progress of research into DNA-alkylating antitumor natural products, including their biosynthesis, modes of action, and auto-resistance mechanisms.
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Productos Biológicos , Alquilantes/farmacología , Productos Biológicos/farmacología , Vías Biosintéticas , ADNRESUMEN
Understanding how antibiotic-producing bacteria deal with highly reactive chemicals will ultimately guide therapeutic strategies to combat the increasing clinical resistance crisis. Here, we uncovered a distinctive self-defense strategy featured by a secreted oxidoreductase NapU to perform extracellularly oxidative activation and conditionally overoxidative inactivation of a matured prodrug in naphthyridinomycin (NDM) biosynthesis from Streptomyces lusitanus NRRL 8034. It was suggested that formation of NDM first involves a nonribosomal peptide synthetase assembly line to generate a prodrug. After exclusion and prodrug maturation, we identified a pharmacophore-inactivated intermediate, which required reactivation by NapU via oxidative C-H bond functionalization extracellularly to afford NDM. Beyond that, NapU could further oxidatively inactivate the NDM pharmacophore to avoid self-cytotoxicity if they coexist longer than necessary. This discovery represents an amalgamation of sophisticatedly temporal and spatial shielding mode conferring self-resistance in antibiotic biosynthesis from Gram-positive bacteria.
Asunto(s)
Antibacterianos/metabolismo , Profármacos/metabolismo , Streptomyces/metabolismo , Naftiridinas/metabolismo , Oxidación-Reducción , Oxidorreductasas/metabolismo , Péptido Sintasas/metabolismoRESUMEN
Miharamycins are peptidyl nucleoside antibiotics with a unique branched C9 pyranosyl amino acid core and a rare 2-aminopurine moiety. Inactivation of 19 genes in the biosynthetic gene cluster and identification of several unexpected intermediates suggest an alternative biosynthetic pathway, which is further supported by feeding experiments and in vitro characterization of an unusual adenylation domain recognizing a complex nucleoside derivative as the substrate. These results thereby provide an unprecedented biosynthetic route of high-carbon sugar catalyzed by atypical hybrid nonribosomal peptide synthetase-polyketide synthase.
Asunto(s)
Proteínas Bacterianas/metabolismo , Nucleósidos/metabolismo , Péptido Sintasas/metabolismo , Sintasas Poliquetidas/metabolismo , Streptomyces/metabolismo , Azúcares/metabolismo , Proteínas Bacterianas/genética , Vías Biosintéticas , Familia de Multigenes , Nucleósidos/genética , Péptido Sintasas/genética , Sintasas Poliquetidas/genética , Streptomyces/genéticaRESUMEN
Covering: 2012 to 2019HemN-like radical S-adenosyl-l-methionine (SAM) enzymes have been recently disclosed to catalyze diverse chemically challenging reactions from primary to secondary metabolic pathways. In this highlight, we summarize the reaction examples catalyzed by HemN-like enzymes to date and the enzymatic mechanisms reported. From the recent mechanistic investigations, we reason that there is a shared initiating mechanism wherein a characteristic SAM methylene radical is proposed to abstract a hydrogen atom from an sp3 carbon or add onto an sp2 carbon center although variations occur thereafter from reaction to reaction, as well as providing a brief insight into some future prospects.
Asunto(s)
Enzimas/química , Enzimas/metabolismo , S-Adenosilmetionina/metabolismo , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Coproporfirinógeno Oxidasa/química , Coproporfirinógeno Oxidasa/metabolismo , Duocarmicinas/metabolismo , Proteínas de Escherichia coli/metabolismo , Hemo/metabolismo , Hidrógeno , Metilación , Péptidos Cíclicos/metabolismo , Policétidos/metabolismo , Proteína Metiltransferasas/metabolismo , Tiazoles/metabolismoRESUMEN
Ranking among the most effective anticancer drugs, anthracyclines represent an important family of aromatic polyketides generated by type II polyketide synthases (PKSs). After formation of polyketide cores, the post-PKS tailoring modifications endow the scaffold with various structural diversities and biological activities. Here we demonstrate an unprecedented four-enzyme-participated hydroxyl regioisomerization process involved in the biosynthesis of kosinostatin. First, KstA15 and KstA16 function together to catalyze a cryptic hydroxylation of the 4-hydroxyl-anthraquinone core, yielding a 1,4-dihydroxyl product, which undergoes a chemically challenging asymmetric reduction-dearomatization subsequently acted by KstA11; then, KstA10 catalyzes a region-specific reduction concomitant with dehydration to afford the 1-hydroxyl anthraquinone. Remarkably, the shunt product identifications of both hydroxylation and reduction-dehydration reactions, the crystal structure of KstA11 with bound substrate and cofactor, and isotope incorporation experiments reveal mechanistic insights into the redox dearomatization and rearomatization steps. These findings provide a distinguished tailoring paradigm for type II PKS engineering.
Asunto(s)
Aminoglicósidos/biosíntesis , Antraciclinas/metabolismo , Proteínas Bacterianas/metabolismo , Enzimas/metabolismo , Aminoglicósidos/química , Antraciclinas/química , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Biocatálisis , Vías Biosintéticas , Enzimas/química , Enzimas/genética , Micromonospora/genética , Micromonospora/metabolismo , Modelos Moleculares , Estructura Molecular , Mutación , Dominios Proteicos , EstereoisomerismoRESUMEN
A number of strategies have been developed to mine novel natural products based on biosynthetic gene clusters and there have been dozens of successful cases facilitated by the development of genomic sequencing. During our study on biosynthesis of the antitumor polyketide kosinostatin (KST), we found that the genome of Micromonospora sp. strain TP-A0468, the producer of KST, contains other potential polyketide gene clusters, with no encoded products detected. Deletion of kst cluster led to abolishment of KST and the enrichment of several new compounds, which were isolated and characterized as 16-demethylrifamycins (referred to here as compounds 3 to 6). Transcriptional analysis demonstrated that the expression of the essential genes related to the biosynthesis of compounds 3 to 6 was comparable to the level in the wild-type and in the kst cluster deletion strain. This indicates that the accumulation of these compounds was due to the redirection of metabolic flux rather than transcriptional activation. Genetic disruption, chemical complementation, and bioinformatic analysis revealed that the production of compounds 3 to 6 was accomplished by cross talk between the two distantly placed polyketide gene clusters pks3 and M-rif This finding not only enriches the analogue pool and the biosynthetic diversity of rifamycins but also provides an auxiliary strategy for natural product discovery through genome mining in polyketide-producing microorganisms.IMPORTANCE Natural products are essential in the development of novel clinically used drugs. Discovering new natural products and modifying known compounds are still the two main ways to generate new candidates. Here, we have discovered several rifamycins with varied skeleton structures by redirecting the metabolic flux from the predominant polyketide biosynthetic pathway to the rifamycin pathway in the marine actinomycetes species Micromonospora sp. strain TP-A0468. Rifamycins are indispensable chemotherapeutics in the treatment of various diseases such as tuberculosis, leprosy, and AIDS-related mycobacterial infections. This study exemplifies a useful method for the discovery of cryptic natural products in genome-sequenced microbes. Moreover, the 16-demethylrifamycins and their genetically manipulable producer provide a new opportunity in the construction of novel rifamycin derivates to aid in the defense against the ever-growing drug resistance of Mycobacterium tuberculosis.
Asunto(s)
Aminoglicósidos/biosíntesis , Aminoglicósidos/genética , Antibacterianos/biosíntesis , Antibacterianos/farmacología , Descubrimiento de Drogas , Micromonospora/genética , Micromonospora/metabolismo , Aminoglicósidos/farmacología , Secuencia de Bases , Vías Biosintéticas/genética , Eliminación de Gen , Lactamas Macrocíclicas/metabolismo , Familia de Multigenes/genética , Policétidos/metabolismo , Rifamicinas/biosíntesis , Metabolismo Secundario/genéticaRESUMEN
One biosynthetic gene cluster (BGC) usually governs the biosynthesis of a series of compounds exhibiting either the same or similar molecular scaffolds. Reported here is a multiplex activation strategy to awaken a cryptic BGC associated with tetracycline polyketides, resulting in the discovery of compounds having different core structures. By constitutively expressing a positive regulator gene in tandem mode, a single BGC directed the biosynthesis of eight aromatic polyketides with two types of frameworks, two pentacyclic isomers and six glycosylated tetracyclines. The proposed biosynthetic pathway, based on systematic gene inactivation and identification of intermediates, employs two sets of tailoring enzymes with a branching point from the same intermediate. These findings not only provide new insights into the role of tailoring enzymes in the diversification of polyketides, but also highlight a reliable strategy for genome mining of natural products.
Asunto(s)
Familia de Multigenes , Policétidos/química , Policétidos/metabolismo , Streptomyces/genética , Streptomyces/metabolismo , Perfilación de la Expresión Génica , Genes Bacterianos , Microorganismos Modificados Genéticamente , Estructura Molecular , Mutación , Regiones Promotoras GenéticasRESUMEN
Oxygen-containing heterocycles are widely encountered in natural products that display diverse pharmacological properties and have potential benefits to human health. The formation of O-heterocycles catalyzed by different types of enzymes in the biosynthesis of natural products not only contributes to the structural diversity of these compounds, but also enriches our understanding of nature's ability to construct complex molecules. This minireview focuses on the various modes of enzymatic O-heterocyclization identified in natural product biosynthesis and summarizes the possible mechanisms involved in ring closure.
Asunto(s)
Productos Biológicos/metabolismo , Enzimas , Compuestos Heterocíclicos/metabolismo , Oxígeno/metabolismo , Catálisis , Ciclización , Enzimas/química , Enzimas/metabolismoRESUMEN
Using a highly effective heterologous expression system, the YM-216391 (1) biosynthetic gene cluster was engineered to yield aurantizolicin (2) and the hybrid compound 3. Both of these compounds were isolated and fully structurally characterised and the bioactivity was evaluated. The results indicate that compound 3 exhibits significantly improved antitumor activity.
Asunto(s)
Antineoplásicos/metabolismo , Vías Biosintéticas , Oxazoles/metabolismo , Péptidos Cíclicos/metabolismo , Streptomyces coelicolor/metabolismo , Streptomyces/metabolismo , Secuencia de Aminoácidos , Antineoplásicos/química , Antineoplásicos/farmacología , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Genes Bacterianos , Ingeniería Genética , Humanos , Familia de Multigenes , Neoplasias/tratamiento farmacológico , Oxazoles/química , Oxazoles/farmacología , Péptidos Cíclicos/química , Péptidos Cíclicos/genética , Péptidos Cíclicos/farmacología , Streptomyces/química , Streptomyces/genética , Streptomyces coelicolor/química , Streptomyces coelicolor/genéticaRESUMEN
Leinamycin (LNM) is a potent antitumor antibiotic produced by Streptomyces atroolivaceus S-140, featuring an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring. Upon reductive activation in the presence of cellular thiols, LNM exerts its antitumor activity by an episulfonium ion-mediated DNA alkylation. Previously, we have cloned the lnm gene cluster from S. atroolivaceus S-140 and characterized the biosynthetic machinery responsible for the 18-membered lactam backbone and the alkyl branch at C3 of LNM. We now report the isolation and characterization of leinamycin E1 (LNM E1) from S. atroolivacues SB3033, a ΔlnmE mutant strain of S. atroolivaceus S-140. Complementary to the reductive activation of LNM by cellular thiols, LNM E1 can be oxidatively activated by cellular reactive oxygen species (ROS) to generate a similar episulfonium ion intermediate, thereby alkylating DNA and leading to eventual cell death. The feasibility of exploiting LNM E1 as an anticancer prodrug activated by ROS was demonstrated in two prostate cancer cell lines, LNCaP and DU-145. Because many cancer cells are under higher cellular oxidative stress with increased levels of ROS than normal cells, these findings support the idea of exploiting ROS as a means to target cancer cells and highlight LNM E1 as a novel lead for the development of anticancer prodrugs activated by ROS. The structure of LNM E1 also reveals critical new insights into LNM biosynthesis, setting the stage to investigate sulfur incorporation, as well as the tailoring steps that convert the nascent hybrid peptide-polyketide biosynthetic intermediate into LNM.
Asunto(s)
Antineoplásicos/metabolismo , Lactamas/metabolismo , Macrólidos/metabolismo , Profármacos/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Tiazoles/metabolismo , Tionas/metabolismo , Antineoplásicos/química , Antineoplásicos/farmacología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Humanos , Lactamas/química , Macrólidos/química , Espectroscopía de Resonancia Magnética , Masculino , Estructura Molecular , Profármacos/química , Profármacos/farmacología , Neoplasias de la Próstata/metabolismo , Neoplasias de la Próstata/patología , Streptomyces/genética , Streptomyces/metabolismo , Tiazoles/química , Tionas/químicaRESUMEN
As a commercial antibiotic, bicyclomycin (BCM) is currently the only known natural product targeting the transcription termination factor rho. It belongs to a family of highly functionalized diketopiperazine (DKP) alkaloids and bears a unique O-bridged bicyclo[4.2.2]piperazinedione ring system, a C1 triol, and terminal exo-methylene groups. We have identified and characterized the BCM biosynthetic pathway by heterologous biotransformations, inâ vitro biochemical assays, and one-pot enzymatic synthesis. A tRNA-dependent cyclodipeptide synthase guides the heterodimerization of leucine and isoleucine to afford the DKP precursor; subsequently, six redox enzymes, including five α-ketoglutarate/Fe2+ -dependent dioxygenases and one cytochrome P450 monooxygenase, regio- and stereoselectively install four hydroxy groups (primary, secondary, and two tertiary), an exo-methylene moiety, and a medium-sized bridged ring through the functionalization of eight unactivated C-H bonds.
Asunto(s)
Antibacterianos/metabolismo , Oxidorreductasas/química , Antibacterianos/química , Compuestos Bicíclicos Heterocíclicos con Puentes/química , Compuestos Bicíclicos Heterocíclicos con Puentes/metabolismo , Carbono/química , Cromatografía Liquida , Dimerización , Genes Bacterianos , Hidrógeno/química , Espectrometría de Masas , Familia de Multigenes , Péptido Sintasas/metabolismo , ARN de Transferencia/química , Streptomyces/genéticaRESUMEN
Aromatic-fused γ-pyrones are structural features of many bioactive natural products and valid scaffolds for medicinal chemistry. However, the enzymology of their formation has not been completely established. Now it is demonstrated that TxnO9, a CalC-like protein belonging to a START family, functions as an unexpected anthraquinone-γ-pyrone synthase involved in the biosynthesis of antitumor antibiotic trioxacarcinâ A (TXN-A). Structural analysis by NMR identified a likely substrate/product-binding mode and putative key active sites of TxnO9, which allowed an enzymatic mechanism to be proposed. Moreover, a subset of uncharacterized homologous proteins bearing an unexamined Lys-Thr dyad exhibit the same function. Therefore, the functional assignment and mechanistic investigation of this γ-pyrone synthase elucidated an undescribed step in TXN-A biosynthesis, and the discovery of this new branch of polyketide heterocyclases expands the functions of the START superfamily.
Asunto(s)
Aminoglicósidos/biosíntesis , Antraquinonas/química , Antibióticos Antineoplásicos/biosíntesis , Ligasas/metabolismo , Policétidos/metabolismo , Pironas/química , Aminoglicósidos/química , Antibióticos Antineoplásicos/química , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Estructura MolecularRESUMEN
Apart from its vital role as the terminal electron acceptor in oxidative phosphorylation in nature, dioxygen also serves as a universal agent which diversifies natural products by oxidative transformations. Ferrous iron and α-ketoglutarate (αKG)-dependent dioxygenases (αKGDs) are versatile enzymes that use dioxygen as an oxidant to catalyse various reactions via CH bond activation, including hydroxylation, dealkylation, desaturation, epoxidation, epimerisation, halogenation, cyclisation, peroxide formation, and ring expansion/contraction reactions. This review updates the reported αKGDs that catalyse reactions related to microbial natural product biosynthesis in the past 10 years. We hope that the versatility of αKGDs shown here can serve as an inspiration for future engineering and catalyst design, which could provide alternative methods to meet the on-going demand for fine chemicals and pharmaceutics.
Asunto(s)
Bacterias/enzimología , Productos Biológicos/metabolismo , Complejo Cetoglutarato Deshidrogenasa/metabolismo , Oxidación-Reducción , Productos Biológicos/química , Catálisis , Cristalografía por Rayos X , Compuestos Ferrosos/metabolismo , Hidroxilación , Hierro/metabolismo , Complejo Cetoglutarato Deshidrogenasa/química , Complejo Cetoglutarato Deshidrogenasa/genética , Oxígeno/metabolismoRESUMEN
The biosynthesis of antibiotics in bacteria is usually believed to be an intracellular process, at the end of which the matured compounds are exported outside the cells. The biosynthesis of saframycinâ A (SFM-A), an antitumor antibiotic, requires a cryptic fatty acyl chain to guide the construction of a pentacyclic tetrahydroisoquinoline scaffold; however, the follow-up deacylation and deamination steps remain unknown. Herein we demonstrate that SfmE, a membrane-bound peptidase, hydrolyzes the fatty acyl chain to release the amino group; and SfmCy2, a secreted oxidoreductase covalently associated with FAD, subsequently performs an oxidative deamination extracellularly. These results not only fill in the missing steps of SFM-A biosynthesis, but also reveal that a FAD-binding oxidoreductase catalyzes an unexpected deamination reaction through an unconventional extracellular pathway in Streptmyces bacteria.
Asunto(s)
Antibióticos Antineoplásicos/biosíntesis , Oxidorreductasas/metabolismo , Profármacos/metabolismo , Antibióticos Antineoplásicos/química , Biocatálisis , Desaminación , Flavina-Adenina Dinucleótido/química , Isoquinolinas/química , Isoquinolinas/metabolismo , Profármacos/química , Streptomyces/metabolismoRESUMEN
The cyclic adenosine monophosphate (cAMP) receptor protein/fumarate and nitrate reductase regulatory protein (Crp/Fnr) family of transcriptional regulators are pleiotropic transcriptional regulators that control a broad range of cellular functions. Leinamycin (LNM) is a potent antitumor antibiotic produced by Streptomyces atroolivaceus S-140. We previously cloned and characterized the lnm biosynthetic gene cluster from S. atroolivaceus S-140. We here report inactivation of lnmO in S. atroolivaceus S-140 and overexpression of lnmO in the S. atroolivaceus S-140 wild-type and ∆lnmE mutant SB3033 to investigate its role in LNM biosynthesis. Bioinformatics analysis revealed LnmO as the only regulator within the lnm gene cluster, exhibiting high sequence similarity to known Crp/Fnr family regulators. The inactivation of lnmO in S. atroolivaceus S-140 completely abolished LNM production but caused no apparent morphological changes, supporting that LnmO is indispensable and specific to LNM biosynthesis. Overexpression of lnmO in S. atroolivaceus S-140 and SB3033 resulted in three- and fourfold increase in LNM and LNM E1 production, respectively, supporting that LnmO acts as a positive regulator. While all of the Crp/Fnr family regulators studied to date appeared to be pleiotropic, our results support LnmO as the first Crp/Fnr family regulator that is pathway-specific. LnmO joins the growing list of regulators that could be exploited to improve secondary metabolite production in Streptomyces. Engineered strains overproducing LNM and LNM E1 will facilitate further mechanistic studies and clinical evaluation of LNM and LNM E1 as novel anticancer drugs.