Understanding the early stages of peptide formation during the biosynthesis of teicoplanin and related glycopeptide antibiotics

Resurrecting ancestral antibiotics: unveiling the origins of modern lipid II targeting glycopeptides

Antibiotics are central to modern medicine, and yet they are mainly the products of intra and inter-kingdom evolutionary warfare. To understand how nature evolves antibiotics around a common mechanism of action, we investigated the origins of an extremely valuable class of compounds, lipid II targeting glycopeptide antibiotics (GPAs, exemplified by teicoplanin and vancomycin), which are used as last resort for the treatment of antibiotic resistant bacterial infections. Using a molecule-centred approach and computational techniques, we first predicted the nonribosomal peptide synthetase assembly line of paleomycin, the ancestral parent of lipid II targeting GPAs. Subsequently, we employed synthetic biology techniques to produce the predicted peptide and validated its antibiotic activity. We revealed the structure of paleomycin, which enabled us to address how nature morphs a peptide antibiotic scaffold through evolution. In doing so, we obtained temporal snapshots of key selection domains in nonribosomal peptide synthesis during the biosynthetic journey from ancestral, teicoplanin-like GPAs to modern GPAs such as vancomycin. Our study demonstrates the synergy of computational techniques and synthetic biology approaches enabling us to journey back in time, trace the temporal evolution of antibiotics, and revive these ancestral molecules. It also reveals the optimisation strategies nature has applied to evolve modern GPAs, laying the foundation for future efforts to engineer this important class of antimicrobial agents.

Adenylation Domain-Guided Recruitment of Trans-Acting Nonheme Monooxygenases in Nonribosomal Peptide Biosynthesis

Nonheme diiron monooxygenases (NHDMs) interact with nonribosomal peptide synthetase (NRPS) assembly lines to install β-hydroxylations at thiolation-domain-bound amino acids during nonribosomal peptide biosynthesis. The high potential of this enzyme family to diversify the products of engineered assembly lines is disproportionate to the currently small knowledge about their structures and mechanisms of substrate recognition. Here, we report the crystal structure of FrsH, the NHDM which catalyzes the β-hydroxylation of l-leucines during biosynthesis of the depsipeptide G protein inhibitor FR900359. Using biophysical approaches, we provide evidence that FrsH interacts with the cognate monomodular NRPS FrsA. By AlphaFold modeling and mutational studies, we detect and examine structural features within the assembly line crucial to recruit FrsH for leucine β-hydroxylation. These are, in contrast to cytochrome-dependent NRPS β-hydroxylases, not located on the thiolation domain, but on the adenylation domain. FrsH can be functionally substituted by homologous enzymes from biosyntheses of the cell-wall-targeting antibiotics lysobactin and hypeptin, indicating that these features are generally applicable to members of the family of trans-acting NHDMs. These insights give important directions for the construction of artificial assembly lines to yield bioactive and chemically complex peptide products.

Beyond vancomycin: recent advances in the modification, reengineering, production and discovery of improved glycopeptide antibiotics to tackle multidrug-resistant bacteria

Glycopeptide antibiotics (GPAs), which include vancomycin and teicoplanin, are important last-resort antibiotics used to treat multidrug-resistant Gram-positive bacterial infections. Whilst second-generation GPAs - generated through chemical modification of natural GPAs - have proven successful, the emergence of GPA resistance has underlined the need to develop new members of this compound class. Significant recent advances have been made in GPA research, including gaining an in-depth understanding of their biosynthesis, improving titre in production strains, developing new derivatives via novel chemical modifications and identifying a new mode of action for structurally diverse type-V GPAs. Taken together, these advances demonstrate significant untapped potential for the further development of GPAs to tackle the growing threat of multidrug-resistant bacteria.

Nyuzenamide C, an Antiangiogenic Epoxy Cinnamic Acid-Containing Bicyclic Peptide from a Riverine Streptomyces sp

A new nonribosomal peptide, nyuzenamide C (1), was discovered from riverine sediment-derived Streptomyces sp. DM14. Comprehensive analysis of the spectroscopic data of nyuzenamide C (1) revealed that 1 has a bicyclic backbone composed of six common amino acid residues (Asn, Leu, Pro, Gly, Val, and Thr) and four nonproteinogenic amino acid units, including hydroxyglycine, β-hydroxyphenylalanine, p-hydroxyphenylglycine, and 3,β-dihydroxytyrosine, along with 1,2-epoxypropyl cinnamic acid. The absolute configuration of 1 was proposed by J-based configuration analysis, the advanced Marfey's method, quantum mechanics-based DP4 calculations, and bioinformatic analysis of its nonribosomal peptide synthetase biosynthetic gene cluster. Nyuzenamide C (1) displayed antiangiogenic activity in human umbilical vein endothelial cells and induced quinone reductase in murine Hepa-1c1c7 cells.

Biotechnological production optimization of argyrins - a potent immunomodulatory natural product class

Argyrins represent a family of cyclic octapeptides exhibiting promising immunomodulatory activity via inhibiting mitochondrial protein synthesis, which leads to reduced IL-17 production by the T-helper 17 cells. Argyrins are formed by a non-ribosomal peptide synthetase (NRPS), originating from the myxobacterial producer strains Archangium gephyra Ar8082 and Cystobacter sp. SBCb004. In this work, a previously established heterologous production platform was employed to provide evidence of direct D-configured amino acid incorporation by the argyrin assembly line. An adenylation domain of the argyrin NRPS was characterized and shown to have a high preference for D-configured amino acids. Eight novel argyrin derivatives were generated via biosynthetic engineering of the heterologous production system. The system was also optimized to enable formation of methylated argyrin C and D derivatives with improved immunosuppressive activity compared with their unmethylated counterparts. Furthermore, the optimization of cultivation conditions allowed exclusive production of one major derivative at a time, drastically improving the purification process. Importantly, engineering of transcription and translation initiation resulted in a substantially improved production titre reaching 350-400 mg l^-1 . The optimized system presented herein thus provides a versatile platform for production of this promising class of immunosuppressants at a scale that should provide sufficient supply for upcoming pre-clinical development.

Genomic-Led Discovery of a Novel Glycopeptide Antibiotic by Nonomuraea coxensis DSM 45129

Glycopeptide antibiotics (GPAs) are last defense line drugs against multidrug-resistant Gram-positive pathogens. Natural GPAs teicoplanin and vancomycin, as well as semisynthetic oritavancin, telavancin, and dalbavancin, are currently approved for clinical use. Although these antibiotics remain efficient, emergence of novel GPA-resistant pathogens is a question of time. Therefore, it is important to investigate the natural variety of GPAs coming from so-called “rare” actinobacteria. Herein we describe a novel GPA producer—Nonomuraea coxensis DSM 45129. Its de novo sequenced and completely assembled genome harbors a biosynthetic gene cluster (BGC) similar to the dbv BGC of A40926, the natural precursor to dalbavancin. The strain produces a novel GPA, which we propose is an A40926 analogue lacking the carboxyl group on the N-acylglucosamine moiety. This structural difference correlates with the absence of dbv29—coding for an enzyme responsible for the oxidation of the N-acylglucosamine moiety. Introduction of dbv29 into N. coxensis led to A40926 production in this strain. Finally, we successfully applied dbv3 and dbv4 heterologous transcriptional regulators to trigger and improve A50926 production in N. coxensis, making them prospective tools for screening other Nonomuraea spp. for GPA production. Our work highlights genus Nonomuraea as a still untapped source of novel GPAs.

Comparative genomics and transcriptomics analyses provide insights into the high yield and regulatory mechanism of Norvancomycin biosynthesis in Amycolatopsis orientalis NCPC 2-48

Background

Norvancomycin has been widely used in clinic to treat against MRSA (Methicillin-resistant Staphylococcus aureus) and MRSE (Methicillin-resistant Staphylococcus epidermidis) infections in China. Amycolatopsis orientalis NCPC 2-48, a high yield strain derived from A. orientalis CPCC 200066, has been applied in industrial large-scale production of norvancomycin by North China Pharmaceutical Group. However, the potential high-yield and regulatory mechanism involved in norvancomycin biosynthetic pathway has not yet been addressed.

Results

Here we sequenced and compared the genomes and transcriptomes of A. orientalis CPCC 200066 and NCPC 2-48. These two genomes are extremely similar with an identity of more than 99.9%, and no duplication and structural variation was found in the norvancomycin biosynthetic gene cluster. Comparative transcriptomic analysis indicated that biosynthetic genes of norvancomycin, as well as some primary metabolite pathways for the biosynthetic precursors of norvancomycin were generally upregulated. AoStrR1 and AoLuxR1, two cluster-situated regulatory genes in norvancomycin cluster, were 23.3-fold and 5.8-fold upregulated in the high yield strain at 48 h, respectively. Over-expression of AoStrR1 and AoLuxR1 in CPCC 200066 resulted in an increase of norvancomycin production, indicating their positive roles in norvancomycin biosynthesis. Furthermore, AoStrR1 can regulate the production of norvancomycin by directly interacting with at least 8 promoters of norvancomycin biosynthetic genes or operons.

Conclusion

Our results suggested that the high yield of NCPC 2-48 can be ascribed to increased expression level of norvancomycin biosynthetic genes in its cluster as well as the genes responsible for the supply of its precursors. The norvancomycin biosynthetic genes are presumably regulated by AoStrR1 and AoLuxR1, of them AoStrR1 is possibly the ultimate pathway-specific regulator for the norvancomycin production. These results are helpful for further clarification of the holistic and pathway-specific regulatory mechanism of norvancomycin biosynthesis in the industrial production strain.

Functional Cross-Talk of MbtH-Like Proteins During Thaxtomin Biosynthesis in the Potato Common Scab Pathogen Streptomyces scabiei

Thaxtomin A is a potent phytotoxin that serves as the principle pathogenicity determinant of the common scab pathogen, Streptomyces scabiei, and is also a promising natural herbicide for agricultural applications. The biosynthesis of thaxtomin A involves the non-ribosomal peptide synthetases (NRPSs) TxtA and TxtB, and an MbtH-like protein (MLP), TxtH, which may function as a chaperone by promoting the proper folding of the two NRPS enzymes in S. scabiei. MLPs are required for the proper function of many NRPS enzymes in bacteria, and they are often capable of interacting with NRPSs from different biosynthetic pathways, though the mechanism by which this occurs is still poorly understood. To gain additional insights into MLP functional cross-talk, we conducted a broad survey of MLPs from diverse phylogenetic lineages to determine if they could functionally replace TxtH. The MLPs were assessed using a protein solubility assay to determine whether they could promote the soluble expression of the TxtA and TxtB adenylation domains. In addition, the MLPs were tested for their ability to restore thaxtomin production in a S. scabiei mutant that lacked TxtH and other endogenous MLPs. Our results showed that the MLPs investigated vary in their ability to exhibit functional cross-talk with TxtH, with two of the MLPs being unable to compensate for the loss of TxtH in the assays performed. The ability of an MLP to serve as a functional partner for the thaxtomin NRPS was not correlated with its overall amino acid similarity with TxtH, but instead with the presence of highly conserved residues. In silico structural analysis of TxtH in association with the TxtA and TxtB adenylation domains revealed that several such residues are situated at the predicted interaction interface, suggesting that they might be critical for promoting functional interactions between MLPs and the thaxtomin NRPS enzymes. Overall, our study provides additional insights into the mechanism of MLP cross-talk, and it enhances our understanding of the thaxtomin biosynthetic machinery. It is anticipated that our findings will have useful applications for both the control of common scab disease and the commercial production of thaxtomin A for agricultural use.

Redesign of Substrate Selection in Glycopeptide Antibiotic Biosynthesis Enables Effective Formation of Alternate Peptide Backbones

Nonribosomal peptide synthesis is capable of utilizing a wide range of amino acid residues due to the selectivity of adenylation (A)-domains. Changing the selectivity of A-domains could lead to new bioactive nonribosomal peptides, although remodeling efforts of A-domains are often unsuccessful. Here, we explored and successfully reengineered the specificity of the module 3 A-domain from glycopeptide antibiotic biosynthesis to change the incorporation of 3,5-dihydroxyphenylglycine into 4-hydroxyphenylglycine. These engineered A-domains remain selective in a functioning peptide assembly line even under substrate competition conditions and indicate a possible application of these for the future redesign of GPA biosynthesis.

Exploring modular reengineering strategies to redesign the teicoplanin non-ribosomal peptide synthetase

Non-ribosomal peptide synthesis is an important biosynthesis pathway in secondary metabolism. In this study we have investigated modularisation and redesign strategies for the glycopeptide antibiotic teicoplanin. Using the relocation or exchange of domains within the NRPS modules, we have identified how to initiate peptide biosynthesis and explored the requirements for the functional reengineering of both the condensation/adenylation domain and epimerisation/condensation domain interfaces. We have also demonstrated strategies that ensure communication between isolated NRPS modules, leading to new peptide assembly pathways. This provides important insights into NRPS reengineering of glycopeptide antibiotic biosynthesis and has broad implications for the redesign of other NRPS systems.