Structural mechanism of regioselectivity in an unusual bacterial acyl-CoA dehydrogenase

AbstractTerminal alkenes are easily derivatized, making them desirable functional group targets for polyketide synthase (PKS) engineering. However, they are rarely encountered in natural PKS systems. One mechanism for terminal alkene formation in PKSs is through the activity of an acyl-CoA dehydrogenase (ACAD). Herein, we use biochemical and structural analysis to understand the mechanism of terminal alkene formation catalyzed by an γ,δ-ACAD from the biosynthesis of the polyketide natural product FK506, TcsD. While TcsD is homologous to canonical α,β-ACADs, it acts regioselectively at the γ,δ-position and only on α,β-unsaturated substrates. Furthermore, this regioselectivity is controlled by a combination of bulky residues in the active site and a lateral shift in the positioning of the FAD cofactor within the enzyme. Substrate modeling suggests that TcsD utilizes a novel set of hydrogen bond donors for substrate activation and positioning, preventing dehydrogenation at the α,β position of substrates. From the structural and biochemical characterization of TcsD, key residues that contribute to regioselectivity and are unique to the protein family were determined and used to identify other putative γ,δ-ACADs that belong to diverse natural product biosynthetic gene clusters. These predictions are supported by the demonstration that a phylogenetically distant homolog of TcsD also regioselectively oxidizes α,β-unsaturated substrates. This work exemplifies a powerful approach to understand unique enzymatic reactions and will facilitate future enzyme discovery, inform enzyme engineering, and aid natural product characterization efforts.

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Evolution of combinatorial diversity in trans-acyltransferase polyketide synthase assembly lines across bacteria

Nature Communications ◽

10.1038/s41467-021-21163-x ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Eric J. N. Helfrich ◽

Reiko Ueoka ◽

Marc G. Chevrette ◽

Franziska Hemmerling ◽

Xiaowen Lu ◽

...

Keyword(s):

Natural Product ◽

Pseudomonas Syringae ◽

Polyketide Synthase ◽

Gene Clusters ◽

Product Class ◽

Assembly Lines ◽

Evolutionary Patterns ◽

In Trans ◽

Global Classification ◽

Exchange Patterns

AbstractTrans-acyltransferase polyketide synthases (trans-AT PKSs) are bacterial multimodular enzymes that biosynthesize diverse pharmaceutically and ecologically important polyketides. A notable feature of this natural product class is the existence of chemical hybrids that combine core moieties from different polyketide structures. To understand the prevalence, biosynthetic basis, and evolutionary patterns of this phenomenon, we developed transPACT, a phylogenomic algorithm to automate global classification of trans-AT PKS modules across bacteria and applied it to 1782 trans-AT PKS gene clusters. These analyses reveal widespread exchange patterns suggesting recombination of extended PKS module series as an important mechanism for metabolic diversification in this natural product class. For three plant-associated bacteria, i.e., the root colonizer Gynuella sunshinyii and the pathogens Xanthomonas cannabis and Pseudomonas syringae, we demonstrate the utility of this computational approach for uncovering cryptic relationships between polyketides, accelerating polyketide mining from fragmented genome sequences, and discovering polyketide variants with conserved moieties of interest. As natural combinatorial hybrids are rare among the more commonly studied cis-AT PKSs, this study paves the way towards evolutionarily informed, rational PKS engineering to produce chimeric trans-AT PKS-derived polyketides.

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Structure elucidation and biosynthesis of fuscachelins, peptide siderophores from the moderate thermophileThermobifida fusca

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0805451105 ◽

2008 ◽

Vol 105 (40) ◽

pp. 15311-15316 ◽

Cited By ~ 48

Author(s):

Eric J. Dimise ◽

Paul F. Widboom ◽

Steven D. Bruner

Keyword(s):

Natural Products ◽

Natural Product ◽

Gene Cluster ◽

Structure Elucidation ◽

Biochemical Characterization ◽

Gene Clusters ◽

Biologically Active ◽

Biosynthetic Gene ◽

Nonribosomal Peptide

Bacteria belonging to the order Actinomycetales have proven to be an important source of biologically active and often therapeutically useful natural products. The characterization of orphan biosynthetic gene clusters is an emerging and valuable approach to the discovery of novel small molecules. Analysis of the recently sequenced genome of the thermophilic actinomyceteThermobifida fuscarevealed an orphan nonribosomal peptide biosynthetic gene cluster coding for an unknown siderophore natural product.T. fuscais a model organism for the study of thermostable cellulases and is a major degrader of plant cell walls. Here, we report the isolation and structure elucidation of the fuscachelins, siderophore natural products produced byT. fusca. In addition, we report the purification and biochemical characterization of the termination module of the nonribosomal peptide synthetase. Biochemical analysis of adenylation domain specificity supports the assignment of this gene cluster as the producer of the fuscachelin siderophores. The proposed nonribosomal peptide biosynthetic pathway exhibits several atypical features, including a macrocyclizing thioesterase that produces a 10-membered cyclic depsipeptide and a nonlinear assembly line, resulting in the unique heterodimeric architecture of the siderophore natural product.

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Discovery of Novel Biosynthetic Gene Cluster Diversity From a Soil Metagenomic Library

Frontiers in Microbiology ◽

10.3389/fmicb.2020.585398 ◽

2020 ◽

Vol 11 ◽

Author(s):

Alinne L. R. Santana-Pereira ◽

Megan Sandoval-Powers ◽

Scott Monsma ◽

Jinglie Zhou ◽

Scott R. Santos ◽

...

Keyword(s):

Natural Product ◽

Soil Microorganisms ◽

Polyketide Synthase ◽

Metagenomic Library ◽

Gene Clusters ◽

Rrna Gene ◽

Type I ◽

Biosynthetic Gene ◽

Pcr Screening ◽

Natural Product Discovery

Soil microorganisms historically have been a rich resource for natural product discovery, yet the majority of these microbes remain uncultivated and their biosynthetic capacity is left underexplored. To identify the biosynthetic potential of soil microorganisms using a culture-independent approach, we constructed a large-insert metagenomic library in Escherichia coli from a topsoil sampled from the Cullars Rotation (Auburn, AL, United States), a long-term crop rotation experiment. Library clones were screened for biosynthetic gene clusters (BGCs) using either PCR or a NGS (next generation sequencing) multiplexed pooling strategy, coupled with bioinformatic analysis to identify contigs associated with each metagenomic clone. A total of 1,015 BGCs were detected from 19,200 clones, identifying 223 clones (1.2%) that carry a polyketide synthase (PKS) and/or a non-ribosomal peptide synthetase (NRPS) cluster, a dramatically improved hit rate compared to PCR screening that targeted type I polyketide ketosynthase (KS) domains. The NRPS and PKS clusters identified by NGS were distinct from known BGCs in the MIBiG database or those PKS clusters identified by PCR. Likewise, 16S rRNA gene sequences obtained by NGS of the library included many representatives that were not recovered by PCR, in concordance with the same bias observed in KS amplicon screening. This study provides novel resources for natural product discovery and circumvents amplification bias to allow annotation of a soil metagenomic library for a more complete picture of its functional and phylogenetic diversity.

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A Concerted Action of UBA5 C-Terminal Unstructured Regions Is Important for Transfer of Activated UFM1 to UFC1

International Journal of Molecular Sciences ◽

10.3390/ijms22147390 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7390

Author(s):

Nicole Wesch ◽

Frank Löhr ◽

Natalia Rogova ◽

Volker Dötsch ◽

Vladimir V. Rogov

Keyword(s):

Cellular Localization ◽

Molecular Mechanisms ◽

Biochemical Characterization ◽

Effective Interaction ◽

Regulatory Region ◽

Titration Calorimetry ◽

Enzymatic Reactions ◽

Cellular Processes ◽

Mechanism Of Interaction

Ubiquitin fold modifier 1 (UFM1) is a member of the ubiquitin-like protein family. UFM1 undergoes a cascade of enzymatic reactions including activation by UBA5 (E1), transfer to UFC1 (E2) and selective conjugation to a number of target proteins via UFL1 (E3) enzymes. Despite the importance of ufmylation in a variety of cellular processes and its role in the pathogenicity of many human diseases, the molecular mechanisms of the ufmylation cascade remains unclear. In this study we focused on the biophysical and biochemical characterization of the interaction between UBA5 and UFC1. We explored the hypothesis that the unstructured C-terminal region of UBA5 serves as a regulatory region, controlling cellular localization of the elements of the ufmylation cascade and effective interaction between them. We found that the last 20 residues in UBA5 are pivotal for binding to UFC1 and can accelerate the transfer of UFM1 to UFC1. We solved the structure of a complex of UFC1 and a peptide spanning the last 20 residues of UBA5 by NMR spectroscopy. This structure in combination with additional NMR titration and isothermal titration calorimetry experiments revealed the mechanism of interaction and confirmed the importance of the C-terminal unstructured region in UBA5 for the ufmylation cascade.

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The Tripod for Bacterial Natural Product Discovery: Genome Mining, Silent Pathway Induction, and Mass Spectrometry-Based Molecular Networking

mSystems ◽

10.1128/msystems.00160-17 ◽

2018 ◽

Vol 3 (2) ◽

Cited By ~ 14

Author(s):

Daniela B. B. Trivella ◽

Rafael de Felicio

Keyword(s):

Mass Spectrometry ◽

Natural Products ◽

Natural Product ◽

Biosynthetic Pathway ◽

Genome Mining ◽

Chemical Compounds ◽

Gene Clusters ◽

Tandem Mass ◽

Molecular Networking ◽

Natural Product Discovery

ABSTRACT Natural products are the richest source of chemical compounds for drug discovery. Particularly, bacterial secondary metabolites are in the spotlight due to advances in genome sequencing and mining, as well as for the potential of biosynthetic pathway manipulation to awake silent (cryptic) gene clusters under laboratory cultivation. Further progress in compound detection, such as the development of the tandem mass spectrometry (MS/MS) molecular networking approach, has contributed to the discovery of novel bacterial natural products. The latter can be applied directly to bacterial crude extracts for identifying and dereplicating known compounds, therefore assisting the prioritization of extracts containing novel natural products, for example. In our opinion, these three approaches—genome mining, silent pathway induction, and MS-based molecular networking—compose the tripod for modern bacterial natural product discovery and will be discussed in this perspective.

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Aromatic Polyketides from a Symbiotic Strain Aspergillus fumigatus D and Characterization of Their Biosynthetic Gene D8.t287

Marine Drugs ◽

10.3390/md18060324 ◽

2020 ◽

Vol 18 (6) ◽

pp. 324

Author(s):

Yi Hua ◽

Rui Pan ◽

Xuelian Bai ◽

Bin Wei ◽

Jianwei Chen ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Polyketide Synthase ◽

Gene Knockout ◽

Gene Clusters ◽

Inhibitory Effect ◽

Genomic Feature ◽

Biosynthetic Gene ◽

Aromatic Polyketides ◽

Staphyloccocus Aureus ◽

Coastal Plant

The chemical investigation of one symbiotic strain, Aspergillus fumigatus D, from the coastal plant Edgeworthia chrysantha Lindl led to the isolation of eight compounds (1–8), which were respectively identified as rubrofusarin B (1), alternariol 9-O-methyl ether (2), fonsecinone D (3), asperpyrone A (4), asperpyrone D (5), fonsecinone B (6), fonsecinone A (7), and aurasperone A (8) by a combination of spectroscopic methods (1D NMR and ESI-MS) as well as by comparison with the literature data. An antimicrobial assay showed that these aromatic polyketides exhibited no remarkable inhibitory effect on Escherichia coli, Staphyloccocus aureus and Candida albicans. The genomic feature of strain D was analyzed, as well as its biosynthetic gene clusters, using antibiotics and Secondary Metabolite Analysis Shell 5.1.2 (antiSMASH). Plausible biosynthetic pathways for dimeric naphtho-γ-pyrones 3–8 were first proposed in this work. A non-reducing polyketide synthase (PKS) gene D8.t287 responsible for the biosynthesis of these aromatic polyketides 1–8 was identified and characterized by target gene knockout experiment and UPLC-MS analysis.

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