1
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Cordoza J, Chen PYT, Blaustein LR, Lima ST, Fiore MF, Chekan JR, Moore BS, McKinnie SMK. Mechanistic and Structural Insights into a Divergent PLP-Dependent l-Enduracididine Cyclase from a Toxic Cyanobacterium. ACS Catal 2023; 13:9817-9828. [PMID: 37497377 PMCID: PMC10367076 DOI: 10.1021/acscatal.3c01294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 06/21/2023] [Indexed: 07/28/2023]
Abstract
Cyclic arginine noncanonical amino acids (ncAAs) are found in several actinobacterial peptide natural products with therapeutically useful antibacterial properties. The preparation of ncAAs like enduracididine and capreomycidine currently takes multiple biosynthetic or chemosynthetic steps, thus limiting the commercial availability and applicability of these cyclic guanidine-containing amino acids. We recently discovered and characterized the biosynthetic pathway of guanitoxin, a potent freshwater cyanobacterial neurotoxin, that contains an arginine-derived cyclic guanidine phosphate within its highly polar structure. The ncAA l-enduracididine is an early intermediate in guanitoxin biosynthesis and is produced by GntC, a unique pyridoxal-5'-phosphate (PLP)-dependent enzyme. GntC catalyzes a cyclodehydration from a stereoselectively γ-hydroxylated l-arginine precursor via a reaction that functionally and mechanistically diverges from previously established actinobacterial cyclic arginine ncAA pathways. Herein, we interrogate l-enduracididine biosynthesis from the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using spectroscopy, stable isotope labeling techniques, and X-ray crystallography structure-guided site-directed mutagenesis. GntC initially facilitates the reversible deprotonations of the α- and β-positions of its substrate before catalyzing an irreversible diastereoselective dehydration and subsequent intramolecular cyclization. The comparison of holo- and substrate-bound GntC structures and activity assays on site-specific mutants further identified amino acid residues that contribute to the overall catalytic mechanism. These interdisciplinary efforts at structurally and functionally characterizing GntC enable an improved understanding of how nature divergently produces cyclic arginine ncAAs and generate additional tools for their biocatalytic production and downstream biological applications.
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Affiliation(s)
- Jennifer
L. Cordoza
- Department
of Chemistry and Biochemistry, University
of California, Santa
Cruz, California 95064, United States
| | - Percival Yang-Ting Chen
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States
| | - Linnea R. Blaustein
- Department
of Chemistry and Biochemistry, University
of California, Santa
Cruz, California 95064, United States
| | - Stella T. Lima
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States
- Center
for Nuclear Energy in Agriculture, University
of São Paulo, Piracicaba, São Paulo 13416-000, Brazil
| | - Marli F. Fiore
- Center
for Nuclear Energy in Agriculture, University
of São Paulo, Piracicaba, São Paulo 13416-000, Brazil
| | - Jonathan R. Chekan
- Center
for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, La Jolla, California 92093, United States
- Department
of Chemistry and Biochemistry, University
of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
| | - Bradley S. Moore
- Department
of Chemistry and Biochemistry, University
of North Carolina at Greensboro, Greensboro, North Carolina 27402, United States
- Skaggs
School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, California 92903, United States
| | - Shaun M. K. McKinnie
- Department
of Chemistry and Biochemistry, University
of California, Santa
Cruz, California 95064, United States
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2
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Caesar LK, Butun FA, Robey MT, Ayon NJ, Gupta R, Dainko D, Bok JW, Nickles G, Stankey RJ, Johnson D, Mead D, Cank KB, Earp CE, Raja HA, Oberlies NH, Keller NP, Kelleher NL. Correlative metabologenomics of 110 fungi reveals metabolite-gene cluster pairs. Nat Chem Biol 2023; 19:846-854. [PMID: 36879060 PMCID: PMC10313767 DOI: 10.1038/s41589-023-01276-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 01/31/2023] [Indexed: 03/08/2023]
Abstract
Natural products research increasingly applies -omics technologies to guide molecular discovery. While the combined analysis of genomic and metabolomic datasets has proved valuable for identifying natural products and their biosynthetic gene clusters (BGCs) in bacteria, this integrated approach lacks application to fungi. Because fungi are hyper-diverse and underexplored for new chemistry and bioactivities, we created a linked genomics-metabolomics dataset for 110 Ascomycetes, and optimized both gene cluster family (GCF) networking parameters and correlation-based scoring for pairing fungal natural products with their BGCs. Using a network of 3,007 GCFs (organized from 7,020 BGCs), we examined 25 known natural products originating from 16 known BGCs and observed statistically significant associations between 21 of these compounds and their validated BGCs. Furthermore, the scalable platform identified the BGC for the pestalamides, demystifying its biogenesis, and revealed more than 200 high-scoring natural product-GCF linkages to direct future discovery.
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Affiliation(s)
- Lindsay K Caesar
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Fatma A Butun
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Matthew T Robey
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
| | - Navid J Ayon
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Raveena Gupta
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - David Dainko
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Jin Woo Bok
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | - Grant Nickles
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
| | | | | | | | - Kristof B Cank
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Cody E Earp
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Huzefa A Raja
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Nicholas H Oberlies
- Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, Greensboro, NC, USA
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Neil L Kelleher
- Department of Chemistry, Northwestern University, Evanston, IL, USA.
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA.
- Proteomics Center of Excellence, Northwestern University, Evanston, IL, USA.
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3
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Huang L, Wang Q, Huang C, Zhou Z, Peng A, Zhang Z. Untargeted Metabolomic Analysis in Endolymphatic Sac Luminal Fluid from Patients with Meniere's Disease. J Assoc Res Otolaryngol 2023; 24:239-251. [PMID: 36715893 PMCID: PMC10121990 DOI: 10.1007/s10162-023-00887-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 12/23/2022] [Indexed: 01/31/2023] Open
Abstract
Dysfunction of the endolymphatic sac (ES) is one of the etiologies of Meniere's disease (MD), the mechanism of which remains unclear. The aim of the present study was to explore the molecular pathological characteristics of ES during the development of MD. Metabolomic profiling of ES luminal fluid from patients with MD and patients with acoustic neuroma (AN) was performed. Diluted ES luminal fluid (ELF) samples were obtained from 10 patients who underwent endolymphatic duct blockage for the treatment of intractable MD and from 6 patients who underwent translabyrinthine surgery for AN. ELF analysis was performed using liquid chromatography-mass spectrometry before the raw data were normalized and subjected to subsequent statistical analysis by MetaboAnalyst. Using thresholds of P ≤ 0.05 and variable important in projection > 1, a total of 111 differential metabolites were screened in the ELF, including 52 metabolites in negative mode and 59 in positive mode. Furthermore, 15 differentially altered metabolites corresponding to 15 compound names were identified using a Student's t-test, including 7 significant increased metabolites and 8 significant decreased metabolites. Moreover, two differentially altered metabolites, hyaluronic acid (HA) and 4-hydroxynonenal (4-HNE), were validated to be upregulated in the epithelial lining of the ES, as well as in the subepithelial connective-tissue in patients with MD comparing with that in patients with AN. Among these differentially altered metabolites, an upregulated expression of HA detected in the ES lumen of the patients with MD was supposed to be associated with the increased endolymph in ES, while an increased level of 4-HNE found in the ELF of the patients with MD provided direct evidence to support that oxidative damage and inflammatory lesions underlie the mechanism of MD. Furthermore, citrate and ethylenediaminetetraacetic acid were detected to be decreased substantially in the ELF of the patients with MD, suggesting the elevated endolymphatic Ca2+ in the ears with chronic endolymphatic hydrops is likely to be associated with the reduction of these two chelators of Ca2+ in ES. The results in the present study indicate metabolomic analysis in the ELF of the patients with MD can potentially improve our understanding on the molecular pathophysiological mechanism in the ES during the development of MD.
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Affiliation(s)
- Li Huang
- Department of Otolaryngology-Head and Neck Surgery, The Second Xiangya Hospital, Central South University, Changsha, 410011 Hunan China
| | - Qin Wang
- Department of Otolaryngology-Head and Neck Surgery, The Second Xiangya Hospital, Central South University, Changsha, 410011 Hunan China
| | - Chao Huang
- Department of Otolaryngology-Head and Neck Surgery, The Second Xiangya Hospital, Central South University, Changsha, 410011 Hunan China
| | - Zhou Zhou
- Department of Otolaryngology-Head and Neck Surgery, The Second Xiangya Hospital, Central South University, Changsha, 410011 Hunan China
| | - Anquan Peng
- Department of Otolaryngology-Head and Neck Surgery, The Second Xiangya Hospital, Central South University, Changsha, 410011 Hunan China
| | - Zhiwen Zhang
- Department of Otolaryngology-Head and Neck Surgery, The Second Xiangya Hospital, Central South University, Changsha, 410011 Hunan China
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4
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Cordoza JL, Chen PYT, Blaustein LR, Lima ST, Fiore MF, Chekan JR, Moore BS, McKinnie SMK. Mechanistic and structural insights into a divergent PLP-dependent L-enduracididine cyclase from a toxic cyanobacterium. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.21.533663. [PMID: 36993528 PMCID: PMC10055224 DOI: 10.1101/2023.03.21.533663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
Cyclic arginine noncanonical amino acids (ncAAs) are found in several actinobacterial peptide natural products with therapeutically useful antibacterial properties. The preparation of ncAAs like enduracididine and capreomycidine currently takes multiple biosynthetic or chemosynthetic steps, thus limiting the commercial availability and applicability of these cyclic guanidine-containing amino acids. We recently discovered and characterized the biosynthetic pathway of guanitoxin, a potent freshwater cya-nobacterial neurotoxin, that contains an arginine-derived cyclic guanidine phosphate within its highly polar structure. The ncAA L-enduracididine is an early intermediate in guanitoxin biosynthesis and is produced by GntC, a unique pyridoxal-5'-phosphate (PLP)-dependent enzyme. GntC catalyzes a cyclodehydration from a stereoselectively γ-hydroxylated L-arginine precursor via a reaction that functionally and mechanistically diverges from previously established actinobacterial cyclic arginine ncAA pathways. Herein, we interrogate L-enduracididine biosynthesis from the cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 using spectroscopic, stable isotope labeling techniques, and X-ray crystal structure-guided site-directed mutagenesis. GntC initially facilitates the reversible deprotonations of the α- and β-positions of its substrate prior to catalyzing an irreversible diastereoselective dehydration and subsequent intramolecular cyclization. The comparison of holo- and substrate bound GntC structures and activity assays on sitespecific mutants further identified amino acid residues that contribute to the overall catalytic mechanism. These interdisciplinary efforts at structurally and functionally characterizing GntC enables an improved understanding of how Nature divergently produces cyclic arginine ncAAs and generates additional tools for their biocatalytic production and downstream biological applications.
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5
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Chen IH, Cheng T, Wang YL, Huang SJ, Hsiao YH, Lai YT, Toh SI, Chu J, Rudolf JD, Chang CY. Characterization and Structural Determination of CmnG-A, the Adenylation Domain That Activates the Nonproteinogenic Amino Acid Capreomycidine in Capreomycin Biosynthesis. Chembiochem 2022; 23:e202200563. [PMID: 36278314 DOI: 10.1002/cbic.202200563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Revised: 10/23/2022] [Indexed: 01/25/2023]
Abstract
Capreomycidine (Cap) is a nonproteinogenic amino acid and building block of nonribosomal peptide (NRP) natural products. We report the formation and activation of Cap in capreomycin biosynthesis. CmnC and CmnD catalyzed hydroxylation and cyclization, respectively, of l-Arg to form l-Cap. l-Cap is then adenylated by CmnG-A before being incorporated into the nonribosomal peptide. The co-crystal structures of CmnG-A with l-Cap and adenosine nucleotides provide insights into the specificity and engineering opportunities of this unique adenylation domain.
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Affiliation(s)
- I-Hsuan Chen
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC.,Institute of Molecular Medicine and Bioengineering, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC
| | - Ting Cheng
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC
| | - Yung-Lin Wang
- Genomics Research Center, Academia Sinica, Taipei, 11529, Taiwan ROC
| | - Szu-Jo Huang
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC
| | - Yu-Hsuan Hsiao
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC
| | - Yi-Ting Lai
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC
| | - Shu-Ing Toh
- Institute of Molecular Medicine and Bioengineering, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC
| | - John Chu
- Department of Chemistry, National Taiwan University, Taipei, 10617, Taiwan, ROC
| | - Jeffrey D Rudolf
- Department of Chemistry, University of Florida, Gainesville, Florida, 32611-7011, USA
| | - Chin-Yuan Chang
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan, ROC.,Center for Intelligent Drug Systems and Smart Bio-devices, National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan ROC.,Department of Biomedical Science and Environment Biology, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan ROC
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6
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Cui Z, Nguyen H, Bhardwaj M, Wang X, Büschleb M, Lemke A, Schütz C, Rohrbacher C, Junghanns P, Koppermann S, Ducho C, Thorson JS, Van Lanen SG. Enzymatic C β-H Functionalization of l-Arg and l-Leu in Nonribosomally Derived Peptidyl Natural Products: A Tale of Two Oxidoreductases. J Am Chem Soc 2021; 143:19425-19437. [PMID: 34767710 DOI: 10.1021/jacs.1c08177] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Muraymycins are peptidyl nucleoside antibiotics that contain two Cβ-modified amino acids, (2S,3S)-capreomycidine and (2S,3S)-β-OH-Leu. The former is also a component of chymostatins, which are aldehyde-containing peptidic protease inhibitors that─like muraymycin─are derived from nonribosomal peptide synthetases (NRPSs). Using feeding experiments and in vitro characterization of 12 recombinant proteins, the biosynthetic mechanism for both nonproteinogenic amino acids is now defined. The formation of (2S,3S)-capreomycidine is shown to involve an FAD-dependent dehydrogenase:cyclase that requires an NRPS-bound pathway intermediate as a substrate. This cryptic dehydrogenation strategy is both temporally and mechanistically distinct in comparison to the biosynthesis of other capreomycidine diastereomers, which has previously been shown to proceed by Cβ-hydroxylation of free l-Arg catalyzed by a member of the nonheme Fe2+- and α-ketoglutarate (αKG)-dependent dioxygenase family and (eventually) a dehydration-mediated cyclization process catalyzed by a distinct enzyme(s). Contrary to our initial expectation, the sole nonheme Fe2+- and αKG-dependent dioxygenase candidate Mur15 encoded within the muraymycin gene cluster is instead demonstrated to catalyze specific Cβ hydroxylation of the Leu residue to generate (2S,3S)-β-OH-Leu that is found in most muraymycin congeners. Importantly, and in contrast to known l-Arg-Cβ-hydroxylases, the Mur15-catalyzed reaction occurs after the NRPS-mediated assembly of the peptide scaffold. This late-stage functionalization affords the opportunity to exploit Mur15 as a biocatalyst, proof of concept of which is provided.
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Affiliation(s)
- Zheng Cui
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
| | - Han Nguyen
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
| | - Minakshi Bhardwaj
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
| | - Xiachang Wang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
| | - Martin Büschleb
- Department of Chemistry, Institute of Organic and Biomolecular Chemistry, Georg-August-University, GöTammannstr. 2, 37077 Göttingen, Germany
| | - Anke Lemke
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany
| | - Christian Schütz
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany
| | - Christian Rohrbacher
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany
| | - Pierre Junghanns
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany
| | - Stefan Koppermann
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany
| | - Christian Ducho
- Department of Pharmacy, Pharmaceutical and Medicinal Chemistry, Saarland University, Campus C2 3, 66123 Saarbrücken, Germany
| | - Jon S Thorson
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
| | - Steven G Van Lanen
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, United States
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7
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Caesar LK, Montaser R, Keller NP, Kelleher NL. Metabolomics and genomics in natural products research: complementary tools for targeting new chemical entities. Nat Prod Rep 2021; 38:2041-2065. [PMID: 34787623 PMCID: PMC8691422 DOI: 10.1039/d1np00036e] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Covering: 2010 to 2021Organisms in nature have evolved into proficient synthetic chemists, utilizing specialized enzymatic machinery to biosynthesize an inspiring diversity of secondary metabolites. Often serving to boost competitive advantage for their producers, these secondary metabolites have widespread human impacts as antibiotics, anti-inflammatories, and antifungal drugs. The natural products discovery field has begun a shift away from traditional activity-guided approaches and is beginning to take advantage of increasingly available metabolomics and genomics datasets to explore undiscovered chemical space. Major strides have been made and now enable -omics-informed prioritization of chemical structures for discovery, including the prospect of confidently linking metabolites to their biosynthetic pathways. Over the last decade, more integrated strategies now provide researchers with pipelines for simultaneous identification of expressed secondary metabolites and their biosynthetic machinery. However, continuous collaboration by the natural products community will be required to optimize strategies for effective evaluation of natural product biosynthetic gene clusters to accelerate discovery efforts. Here, we provide an evaluative guide to scientific literature as it relates to studying natural product biosynthesis using genomics, metabolomics, and their integrated datasets. Particular emphasis is placed on the unique insights that can be gained from large-scale integrated strategies, and we provide source organism-specific considerations to evaluate the gaps in our current knowledge.
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Affiliation(s)
- Lindsay K Caesar
- Department of Chemistry, Northwestern University, Evanston, IL, USA.
| | - Rana Montaser
- Department of Chemistry, Northwestern University, Evanston, IL, USA.
| | - Nancy P Keller
- Department of Medical Microbiology and Immunology and Bacteriology, University of Wisconsin-Madison, Madison, WI, USA
| | - Neil L Kelleher
- Department of Chemistry, Northwestern University, Evanston, IL, USA.
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA
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8
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Cyclofaulknamycin with the Rare Amino Acid D-capreomycidine Isolated from a Well-Characterized Streptomyces albus Strain. Microorganisms 2021; 9:microorganisms9081609. [PMID: 34442689 PMCID: PMC8399532 DOI: 10.3390/microorganisms9081609] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/21/2021] [Accepted: 07/22/2021] [Indexed: 11/17/2022] Open
Abstract
Targeted genome mining is an efficient method of biosynthetic gene cluster prioritization within constantly growing genome databases. Using two capreomycidine biosynthesis genes, alpha-ketoglutarate-dependent arginine beta-hydroxylase and pyridoxal-phosphate-dependent aminotransferase, we identified two types of clusters: one type containing both genes involved in the biosynthesis of the abovementioned moiety, and other clusters including only arginine hydroxylase. Detailed analysis of one of the clusters, the flk cluster from Streptomyces albus, led to the identification of a cyclic peptide that contains a rare D-capreomycidine moiety for the first time. The absence of the pyridoxal-phosphate-dependent aminotransferase gene in the flk cluster is compensated by the XNR_1347 gene in the S. albus genome, whose product is responsible for biosynthesis of the abovementioned nonproteinogenic amino acid. Herein, we report the structure of cyclofaulknamycin and the characteristics of its biosynthetic gene cluster, biosynthesis and bioactivity profile.
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