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Crowe SA, Zhao X, Gan F, Chen X, Hudson GA, Astolfi MCT, Scheller HV, Liu Y, Keasling JD. Engineered Saccharomyces cerevisiae as a Biosynthetic Platform of Nucleotide Sugars. ACS Synth Biol 2024; 13:1215-1224. [PMID: 38467016 DOI: 10.1021/acssynbio.3c00666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Glycosylation of biomolecules can greatly alter their physicochemical properties, cellular recognition, subcellular localization, and immunogenicity. Glycosylation reactions rely on the stepwise addition of sugars using nucleotide diphosphate (NDP)-sugars. Making these substrates readily available will greatly accelerate the characterization of new glycosylation reactions, elucidation of their underlying regulation mechanisms, and production of glycosylated molecules. In this work, we engineered Saccharomyces cerevisiae to heterologously express nucleotide sugar synthases to access a wide variety of uridine diphosphate (UDP)-sugars from simple starting materials (i.e., glucose and galactose). Specifically, activated glucose, uridine diphosphate d-glucose (UDP-d-Glc), can be converted to UDP-d-glucuronic acid (UDP-d-GlcA), UDP-d-xylose (UDP-d-Xyl), UDP-d-apiose (UDP-d-Api), UDP-d-fucose (UDP-d-Fuc), UDP-l-rhamnose (UDP-l-Rha), UDP-l-arabinopyranose (UDP-l-Arap), and UDP-l-arabinofuranose (UDP-l-Araf) using the corresponding nucleotide sugar synthases of plant and microbial origins. We also expressed genes encoding the salvage pathway to directly activate free sugars to achieve the biosynthesis of UDP-l-Arap and UDP-l-Araf. We observed strong inhibition of UDP-d-Glc 6-dehydrogenase (UGD) by the downstream product UDP-d-Xyl, which we circumvented using an induction system (Tet-On) to delay the production of UDP-d-Xyl to maintain the upstream UDP-sugar pool. Finally, we performed a time-course study using strains containing the biosynthetic pathways to produce five non-native UDP-sugars to elucidate their time-dependent interconversion and the role of UDP-d-Xyl in regulating UDP-sugar metabolism. These engineered yeast strains are a robust platform to (i) functionally characterize sugar synthases in vivo, (ii) biosynthesize a diverse selection of UDP-sugars, (iii) examine the regulation of intracellular UDP-sugar interconversions, and (iv) produce glycosylated secondary metabolites and proteins.
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Affiliation(s)
- Samantha A Crowe
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, United States
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Xixi Zhao
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Fei Gan
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Xiaoyue Chen
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, United States
| | - Graham A Hudson
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Maria C T Astolfi
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Department of Bioengineering, University of California, Berkeley, California 94720, United States
| | - Henrik V Scheller
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, United States
| | - Yuzhong Liu
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
| | - Jay D Keasling
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, United States
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, California 94720, United States
- Joint BioEnergy Institute, Emeryville, California 94608, United States
- Department of Bioengineering, University of California, Berkeley, California 94720, United States
- Division of Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
- Center for Synthetic Biochemistry, Shenzhen Institutes for Advanced Technologies, Shenzhen 518071, China
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2
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Lee AR, Carter RS, Imani AS, Dommaraju SR, Hudson GA, Mitchell DA, Freeman MF. Computationally guided exploration of borosin biosynthetic strategies. bioRxiv 2024:2024.01.09.574750. [PMID: 38260703 PMCID: PMC10802470 DOI: 10.1101/2024.01.09.574750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Borosins are ribosomally synthesized and post-translationally modified peptides containing backbone α- N -methylations. Identification of borosin precursor peptides is difficult because (1) there are no conserved sequence elements among borosin precursor peptides and (2) the biosynthetic gene clusters contain numerous domain architectures and peptide fusions. To tackle this problem, we updated the genome mining tool RODEO to automatically evaluate putative borosin BGCs and identify precursor peptides. Enabled by the new borosin module, we analyzed all borosin BGCs found in available sequence data and assigned precursor peptides to previously orphan borosin methyltransferases. Additionally, we bioinformatically predict and experimentally characterize a new fused borosin domain architecture, in which the modified core is N-terminal to the methyltransferase domain. Finally, we demonstrate that a borosin precursor peptide is the native substrate of shewasin A, a previously characterized pepsin-like aspartic peptidase whose native biological function was unknown.
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3
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Luckie BA, Kashyap M, Pearson AN, Chen Y, Liu Y, Valencia LE, Carrillo Romero A, Hudson GA, Tao XB, Wu B, Petzold CJ, Keasling JD. Development of Corynebacterium glutamicum as a monoterpene production platform. Metab Eng 2024; 81:110-122. [PMID: 38056688 DOI: 10.1016/j.ymben.2023.11.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 12/08/2023]
Abstract
Monoterpenes are commonly known for their role in the flavors and fragrances industry and are also gaining attention for other uses like insect repellant and as potential renewable fuels for aviation. Corynebacterium glutamicum, a Generally Recognized as Safe microbe, has been a choice organism in industry for the annual million ton-scale bioproduction of amino acids for more than 50 years; however, efforts to produce monoterpenes in C. glutamicum have remained relatively limited. In this study, we report a further expansion of the C. glutamicum biosynthetic repertoire through the development and optimization of a mevalonate-based monoterpene platform. In the course of our plasmid design iterations, we increased flux through the mevalonate-based bypass pathway, measuring isoprenol production as a proxy for monoterpene precursor abundance and demonstrating the highest reported titers in C. glutamicum to date at 1504.6 mg/L. Our designs also evaluated the effects of backbone, promoter, and GPP synthase homolog origin on monoterpene product titers. Monoterpene production was further improved by disrupting competing pathways for isoprenoid precursor supply and by implementing a biphasic production system to prevent volatilization. With this platform, we achieved 321.1 mg/L of geranoids, 723.6 mg/L of 1,8-cineole, and 227.8 mg/L of linalool. Furthermore, we determined that C. glutamicum first oxidizes geraniol through an aldehyde intermediate before it is asymmetrically reduced to citronellol. Additionally, we demonstrate that the aldehyde reductase, AdhC, possesses additional substrate promiscuity for acyclic monoterpene aldehydes.
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Affiliation(s)
- Bridget A Luckie
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, USA
| | - Meera Kashyap
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Allison N Pearson
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA; Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Yan Chen
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Yuzhong Liu
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA; Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA
| | - Luis E Valencia
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA; Joint Program in Bioengineering, University of California, Berkeley, San Francisco, CA, 94720, USA
| | - Alexander Carrillo Romero
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Graham A Hudson
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA; Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA
| | - Xavier B Tao
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Bryan Wu
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Christopher J Petzold
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Jay D Keasling
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA; Biological Systems & Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA; Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, USA; Joint Program in Bioengineering, University of California, Berkeley, San Francisco, CA, 94720, USA; Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark; Center for Synthetic Biochemistry, Institute for Synthetic Biology, Shenzhen Institutes for Advanced Technologies, Shenzhen, China.
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4
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Chen X, Hudson GA, Mineo C, Amer B, Baidoo EEK, Crowe SA, Liu Y, Keasling JD, Scheller HV. Deciphering triterpenoid saponin biosynthesis by leveraging transcriptome response to methyl jasmonate elicitation in Saponaria vaccaria. Nat Commun 2023; 14:7101. [PMID: 37925486 PMCID: PMC10625584 DOI: 10.1038/s41467-023-42877-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 10/24/2023] [Indexed: 11/06/2023] Open
Abstract
Methyl jasmonate (MeJA) is a known elicitor of plant specialized metabolism, including triterpenoid saponins. Saponaria vaccaria is an annual herb used in traditional Chinese medicine, containing large quantities of oleanane-type triterpenoid saponins with anticancer properties and structural similarities to the vaccine adjuvant QS-21. Leveraging the MeJA-elicited saponin biosynthesis, we identify multiple enzymes catalyzing the oxidation and glycosylation of triterpenoids in S. vaccaria. This exploration is aided by Pacbio full-length transcriptome sequencing and gene expression analysis. A cellulose synthase-like enzyme can not only glucuronidate triterpenoid aglycones but also alter the product profile of a cytochrome P450 monooxygenase via preference for the aldehyde intermediate. Furthermore, the discovery of a UDP-glucose 4,6-dehydratase and a UDP-4-keto-6-deoxy-glucose reductase reveals the biosynthetic pathway for the rare nucleotide sugar UDP-D-fucose, a likely sugar donor for fucosylation of plant natural products. Our work enables the production and optimization of high-value saponins in microorganisms and plants through synthetic biology approaches.
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Affiliation(s)
- Xiaoyue Chen
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Graham A Hudson
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
| | - Charlotte Mineo
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
| | - Bashar Amer
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Edward E K Baidoo
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Samantha A Crowe
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA
| | - Yuzhong Liu
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
| | - Jay D Keasling
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA, 94720, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
- Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
- Center for Synthetic Biochemistry, Shenzhen Institutes for Advanced Technologies, Shenzhen, China
| | - Henrik V Scheller
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA.
- Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA.
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA.
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5
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Nguyen DT, Le TT, Rice AJ, Hudson GA, van der Donk WA, Mitchell DA. Accessing Diverse Pyridine-Based Macrocyclic Peptides by a Two-Site Recognition Pathway. J Am Chem Soc 2022; 144:11263-11269. [PMID: 35713415 PMCID: PMC9247985 DOI: 10.1021/jacs.2c02824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Macrocyclic peptides
are sought-after molecular scaffolds for drug
discovery, and new methods to access diverse libraries are of increasing
interest. Here, we report the enzymatic synthesis of pyridine-based
macrocyclic peptides (pyritides) from linear precursor peptides. Pyritides
are a recently described class of ribosomally synthesized and post-translationally
modified peptides (RiPPs) and are related to the long-known thiopeptide
natural products. RiPP precursors typically contain an N-terminal
leader region that is physically engaged by the biosynthetic proteins
that catalyze modification of the C-terminal core region of the precursor
peptide. We demonstrate that pyritide-forming enzymes recognize both
the leader region and a C-terminal tripeptide motif, with each contributing
to site-selective substrate modification. Substitutions in the core
region were well-tolerated and facilitated the generation of a wide
range of pyritide analogues, with variations in macrocycle sequence
and size. A combination of the pyritide biosynthetic pathway with
azole-forming enzymes was utilized to generate a thiazole-containing
pyritide (historically known as a thiopeptide) with no similarity
in sequence and macrocycle size to the naturally encoded pyritides.
The broad substrate scope of the pyritide biosynthetic enzymes serves
as a future platform for macrocyclic peptide lead discovery and optimization.
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Affiliation(s)
- Dinh T Nguyen
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Tung T Le
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Andrew J Rice
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Wilfred A van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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6
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Hudson GA, Burkhart BJ, DiCaprio AJ, Schwalen CJ, Kille B, Pogorelov TV, Mitchell DA. Correction to "Bioinformatic Mapping of Radical S-Adenosylmethionine-Dependent Ribosomally Synthesized and Post-Translationally Modified Peptides Identifies New Cα, Cβ, and Cγ-Linked Thioether-Containing Peptides". J Am Chem Soc 2021; 143:10479. [PMID: 34197098 DOI: 10.1021/jacs.1c06285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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Harris LA, Saint-Vincent PMB, Guo X, Hudson GA, DiCaprio AJ, Zhu L, Mitchell DA. Reactivity-Based Screening for Citrulline-Containing Natural Products Reveals a Family of Bacterial Peptidyl Arginine Deiminases. ACS Chem Biol 2020; 15:3167-3175. [PMID: 33249828 DOI: 10.1021/acschembio.0c00685] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a family of natural products defined by a genetically encoded precursor peptide that is processed by associated biosynthetic enzymes to form the mature product. Lasso peptides are a class of RiPP defined by an isopeptide linkage between the N-terminal amine and an internal Asp/Glu residue with the C-terminal sequence threaded through the macrocycle. This unique lariat topology, which typically provides considerable stability toward heat and proteases, has stimulated interest in lasso peptides as potential therapeutics. Post-translational modifications beyond the class-defining, threaded macrolactam have been reported, including one example of Arg deimination to yield citrulline (Cit). Although a Cit-containing lasso peptide (i.e., citrulassin) was serendipitously discovered during a genome-guided campaign, the gene(s) responsible for Arg deimination has remained unknown. Herein, we describe the use of reactivity-based screening to discriminate bacterial strains that produce Arg- versus Cit-bearing citrulassins, yielding 13 new lasso peptide variants. Partial phylogenetic profiling identified a distally encoded peptidyl arginine deiminase (PAD) gene ubiquitous to the Cit-containing variants. Absence of this gene correlated strongly with lasso peptide variants only containing Arg (i.e., des-citrulassin). Heterologous expression of the PAD gene in a des-citrulassin producer resulted in the production of the deiminated analog, confirming PAD involvement in Arg deimination. The PADs were then bioinformatically surveyed to provide a deeper understanding of their taxonomic distribution and genomic contexts and to facilitate future studies that will evaluate any additional biochemical roles for the superfamily.
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8
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Hudson GA, Hooper AR, DiCaprio AJ, Sarlah D, Mitchell DA. Structure Prediction and Synthesis of Pyridine-Based Macrocyclic Peptide Natural Products. Org Lett 2020; 23:253-256. [PMID: 32845158 DOI: 10.1021/acs.orglett.0c02699] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural and functional characterization of natural products is vastly outpaced by the bioinformatic identification of biosynthetic gene clusters (BGCs) that encode such molecules. Uniting our knowledge of bioinformatics and enzymology to predict and synthetically access natural products is an effective platform for investigating cryptic/silent BGCs. We report the identification, biosynthesis, and total synthesis of a minimalistic class of ribosomally synthesized and post-translationally modified peptides (RiPPs) with the responsible BGCs encoding a subset of enzymes known from thiopeptide biosynthesis. On the basis of the BGC content, these RiPPs were predicted to undergo enzymatic dehydration of serine followed by [4+2]-cycloaddition to produce a trisubstituted, pyridine-based macrocycle. These RiPPs, termed "pyritides", thus contain the same six-membered, nitrogenous heterocycle that defines the thiopeptide RiPP class but lack the ubiquitous thiazole/thiazoline heterocycles, suggesting that thiopeptides should be reclassified as a more elaborate subclass of the pyritides. One pyritide product was obtained using an 11-step synthesis, and the structure verified by an orthogonal chemoenzymatic route using the precursor peptide and cognate pyridine synthase. This work exemplifies complementary bioinformatics, enzymology, and synthesis to characterize a minimalistic yet structurally intriguing scaffold that, unlike most thiopeptides, lacks growth-suppressive activity toward Gram-positive bacteria.
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Affiliation(s)
- Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Annie R Hooper
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Adam J DiCaprio
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - David Sarlah
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, United States
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9
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Hudson GA, Mitchell DA. Corrigendum to “RiPP antibiotics: biosynthesis and engineering potential” [Curr Opin Microbiol 45 (2018) 61-69]. Curr Opin Microbiol 2019; 49:103. [DOI: 10.1016/j.mib.2019.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Hudson GA, Burkhart BJ, DiCaprio AJ, Schwalen CJ, Kille B, Pogorelov TV, Mitchell DA. Bioinformatic Mapping of Radical S-Adenosylmethionine-Dependent Ribosomally Synthesized and Post-Translationally Modified Peptides Identifies New Cα, Cβ, and Cγ-Linked Thioether-Containing Peptides. J Am Chem Soc 2019; 141:8228-8238. [PMID: 31059252 DOI: 10.1021/jacs.9b01519] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recently developed bioinformatic tools have bolstered the discovery of ribosomally synthesized and post-translationally modified peptides (RiPPs). Using an improved version of Rapid ORF Description and Evaluation Online (RODEO 2.0), a biosynthetic gene cluster mining algorithm, we bioinformatically mapped the sactipeptide RiPP class via the radical S-adenosylmethionine (SAM) enzymes that form the characteristic sactionine (sulfur-to-α carbon) cross-links between cysteine and acceptor residues. Hundreds of new sactipeptide biosynthetic gene clusters were uncovered, and a novel sactipeptide "huazacin" with growth-suppressive activity against Listeria monocytogenes was characterized. Bioinformatic analysis further suggested that a group of sactipeptide-like peptides heretofore referred to as six cysteines in forty-five residues (SCIFFs) might not be sactipeptides as previously thought. Indeed, the bioinformatically identified SCIFF peptide "freyrasin" was demonstrated to contain six thioethers linking the β carbons of six aspartate residues. Another SCIFF, thermocellin, was shown to contain a thioether cross-linked to the γ carbon of threonine. SCIFFs feature a different paradigm of non-α carbon thioether linkages, and they are exclusively formed by radical SAM enzymes, as opposed to the polar chemistry employed during lanthipeptide biosynthesis. Therefore, we propose the renaming of the SCIFF family as radical non-α thioether peptides (ranthipeptides) to better distinguish them from the sactipeptide and lanthipeptide RiPP classes.
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11
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DiCaprio AJ, Firouzbakht A, Hudson GA, Mitchell DA. Enzymatic Reconstitution and Biosynthetic Investigation of the Lasso Peptide Fusilassin. J Am Chem Soc 2018; 141:290-297. [PMID: 30589265 DOI: 10.1021/jacs.8b09928] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Lasso peptides are a class of ribosomally synthesized and post-translationally modified natural product which possess a unique lariat knot conformation. The low entropy "threaded" conformation endows lasso peptides with considerable resistance to heat and proteolytic degradation, which are attractive properties for the development of peptide-based therapeutics. Despite their discovery nearly 30 years ago, the molecular mechanism underlying lasso peptide biosynthesis remains poorly characterized due to the low stability of the purified biosynthetic enzymes. Here, we report the biosynthetic reconstitution of a lasso peptide derived from Thermobifida fusca, termed fusilassin. Beyond robust catalytic activity, the fusilassin enzymes demonstrate extraordinary substrate tolerance during heterologous expression in E. coli and upon purification in cell-free biosynthetic reconstitution reactions. We provide evidence that the fusilassin biosynthetic enzymes are not capable of forming branched-cyclic products but can produce entirely unrelated lasso peptides. Finally, we leveraged our bioinformatic survey of all lasso peptides identified in GenBank to perform coevolutionary analysis of two requisite biosynthetic proteins. This effort correctly identified residues governing an important protein-protein interaction, illustrating how genomic insight can accelerate the characterization of natural product biosynthetic pathways. The fusilassin enzymes described within represent a model system for both designing future lasso peptides of biomedical importance and also for elucidating the molecular mechanisms that govern lasso peptide biosynthesis.
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Affiliation(s)
- Adam J DiCaprio
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Mathews Avenue , Urbana , Illinois 61801 , United States.,Carl R. Woese Institute for Genomic Biology , University of Illinois at Urbana-Champaign , 1206 West Gregory Drive , Urbana , Illinois 61801 , United States
| | - Arash Firouzbakht
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Mathews Avenue , Urbana , Illinois 61801 , United States.,Carl R. Woese Institute for Genomic Biology , University of Illinois at Urbana-Champaign , 1206 West Gregory Drive , Urbana , Illinois 61801 , United States
| | - Graham A Hudson
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Mathews Avenue , Urbana , Illinois 61801 , United States
| | - Douglas A Mitchell
- Department of Chemistry , University of Illinois at Urbana-Champaign , 600 South Mathews Avenue , Urbana , Illinois 61801 , United States.,Carl R. Woese Institute for Genomic Biology , University of Illinois at Urbana-Champaign , 1206 West Gregory Drive , Urbana , Illinois 61801 , United States
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12
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Abstract
The threat of antibiotic resistant bacterial infections continues to underscore the need for new treatment options. Historically, small molecule metabolites from microbes have provided a rich source of antibiotic compounds, and as a result, significant effort has been invested in engineering the responsible biosynthetic pathways to generate novel analogs with attractive pharmacological properties. Unfortunately, biosynthetic stringency has limited the capacity of non-ribosomal peptide synthetases and polyketide synthases from producing substantially different analogs in large numbers. Another class of natural products, the ribosomally synthesized and post-translationally modified peptides (RiPPs), have rapidly expanded in recent years with many natively displaying potent antibiotic activity. RiPP biosynthetic pathways are modular and intrinsically tolerant to alternative substrates. Several prominent RiPPs with antibiotic activity will be covered in this review with a focus on their biosynthetic plasticity. While only a few RiPP enzymes have been thoroughly investigated mechanistically, this knowledge has already been harnessed to generate new-to-nature compounds. Through the use of synthetic biology approaches, on-going efforts in RiPP engineering hold great promise in unlocking the potential of this natural product class.
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Affiliation(s)
- Graham A Hudson
- Department of Chemistry, University of Illinois, 600 S Mathews Ave, Urbana, IL 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois, 600 S Mathews Ave, Urbana, IL 61801, United States; Carl R. Woese Institute for Genomic Biology, University of Illinois, 600 S Mathews Ave, Urbana, IL 61801, United States; Department of Microbiology, University of Illinois, 600 S Mathews Ave, Urbana, IL 61801, United States.
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13
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Abstract
Thiopeptides are members of the ribosomally synthesized and post-translationally modified peptide family of natural products. Most characterized thiopeptides display nanomolar potency toward Gram-positive bacteria by blocking protein translation with several being produced at the industrial scale for veterinary and livestock applications. Employing our custom bioinformatics program, RODEO, we expand the thiopeptide family of natural products by a factor of four. This effort revealed many new thiopeptide biosynthetic gene clusters with products predicted to be distinct from characterized thiopeptides and identified gene clusters for previously characterized molecules of unknown biosynthetic origin. To further validate our data set of predicted thiopeptide biosynthetic gene clusters, we isolated and characterized a structurally unique thiopeptide featuring a central piperidine and rare thioamide moiety. Termed saalfelduracin, this thiopeptide displayed potent antibiotic activity toward several drug-resistant Gram-positive pathogens. A combination of whole-genome sequencing, comparative genomics, and heterologous expression experiments confirmed that the thioamide moiety of saalfelduracin is installed post-translationally by the joint action of two proteins, TfuA and YcaO. These results reconcile the previously unknown origin of the thioamide in two long-known thiopeptides, thiopeptin and Sch 18640. Armed with these new insights into thiopeptide chemical-genomic space, we provide a roadmap for the discovery of additional members of this natural product family.
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Affiliation(s)
- Christopher J. Schwalen
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Graham A. Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Bryce Kille
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Douglas A. Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
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14
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Schwalen CJ, Hudson GA, Kosol S, Mahanta N, Challis GL, Mitchell DA. In Vitro Biosynthetic Studies of Bottromycin Expand the Enzymatic Capabilities of the YcaO Superfamily. J Am Chem Soc 2017; 139:18154-18157. [PMID: 29200283 PMCID: PMC5915351 DOI: 10.1021/jacs.7b09899] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The bottromycins belong to the ribosomally synthesized and posttranslationally modified peptide (RiPP) family of natural products. Bottromycins exhibit unique structural features, including a hallmark macrolactamidine ring and thiazole heterocycle for which divergent members of the YcaO superfamily have been biosynthetically implicated. Here we report the in vitro reconstitution of two YcaO proteins, BmbD and BmbE, responsible for the ATP-dependent cyclodehydration reactions that yield thiazoline- and macrolactamidine-functionalized products, respectively. We also establish the substrate tolerance for BmbD and BmbE and systematically dissect the role of the follower peptide, which we show serves a purpose similar to canonical leader peptides in directing the biosynthetic enzymes to the substrate. Lastly, we leverage the expanded capabilities of YcaO proteins to conduct an extensive bioinformatic survey to classify known YcaO chemistry. This analysis predicts new functions remain to be uncovered within the superfamily.
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Affiliation(s)
- Christopher J. Schwalen
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Graham A. Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Simone Kosol
- Department of Chemistry and Warwick Integrative Synthetic Biology Center, University of Warwick, Coventry CV4 7AL, UK
| | - Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
| | - Gregory L. Challis
- Department of Chemistry and Warwick Integrative Synthetic Biology Center, University of Warwick, Coventry CV4 7AL, UK
- Department of Biochemistry and Molecular Biology and ARC Centre of Excellence in Advanced Molecular Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Douglas A. Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
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15
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Zhang Z, Mahanta N, Hudson GA, Mitchell DA, van der Donk WA. Mechanism of a Class C Radical S-Adenosyl-l-methionine Thiazole Methyl Transferase. J Am Chem Soc 2017; 139:18623-18631. [PMID: 29190095 PMCID: PMC5748327 DOI: 10.1021/jacs.7b10203] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The past decade has seen the discovery of four different classes of radical S-adenosylmethionine (rSAM) methyltransferases that methylate unactivated carbon centers. Whereas the mechanism of class A is well understood, the molecular details of methylation by classes B-D are not. In this study, we present detailed mechanistic investigations of the class C rSAM methyltransferase TbtI involved in the biosynthesis of the potent thiopeptide antibiotic thiomuracin. TbtI C-methylates a Cys-derived thiazole during posttranslational maturation. Product analysis demonstrates that two SAM molecules are required for methylation and that one SAM (SAM1) is converted to 5'-deoxyadenosine and the second SAM (SAM2) is converted to S-adenosyl-l-homocysteine (SAH). Isotope labeling studies show that a hydrogen is transferred from the methyl group of SAM2 to the 5'-deoxyadenosine of SAM1 and the other two hydrogens of the methyl group of SAM2 appear in the methylated product. In addition, a hydrogen appears to be transferred from the β-position of the thiazole to the methyl group in the product. We also show that the methyl protons in the product can exchange with solvent. A mechanism consistent with these observations is presented that differs from other characterized radical SAM methyltransferases.
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Affiliation(s)
- Zhengan Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Wilfred A van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
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16
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17
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Abstract
Ribosomally synthesized and post-translationally modified peptides (RiPPs) display a diverse range of structures and continue to expand as a natural product class. Accordingly, RiPPs exhibit a wide array of bioactivities, acting as broad and narrow spectrum growth suppressors, antidiabetics, and antinociception and anticancer agents. Because of these properties, and the complex repertoire of post-translational modifications (PTMs) that give rise to these molecules, RiPP biosynthesis has been intensely studied. RiPP biosynthesis often involves enzymes that perform unique chemistry with intriguing reaction mechanisms, which attract chemists and biochemists alike to study and re-engineer these pathways. One particular type of RiPP biosynthetic enzyme is the so-called radical S-adenosylmethionine (rSAM) enzyme, which utilizes radical-based chemistry to install several distinct PTMs. Here, we describe the rSAM enzymes characterized over the past decade that catalyze six reaction types from several RiPP biosynthetic pathways. We present the current state of mechanistic understanding and conclude with possible directions for future characterization of this enzyme family.
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Affiliation(s)
- Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
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18
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Burkhart B, Kakkar N, Hudson GA, van der Donk WA, Mitchell DA. Chimeric Leader Peptides for the Generation of Non-Natural Hybrid RiPP Products. ACS Cent Sci 2017; 3:629-638. [PMID: 28691075 PMCID: PMC5492250 DOI: 10.1021/acscentsci.7b00141] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Indexed: 05/21/2023]
Abstract
Combining biosynthetic enzymes from multiple pathways is an attractive approach for producing molecules with desired structural features; however, progress has been hampered by the incompatibility of enzymes from unrelated pathways and intolerance toward alternative substrates. Ribosomally synthesized and posttranslationally modified peptides (RiPPs) are a diverse natural product class that employs a biosynthetic logic that is highly amenable to engineering new compounds. RiPP biosynthetic proteins modify their substrates by binding to a motif typically located in the N-terminal leader region of the precursor peptide. Here, we exploit this feature by designing leader peptides that enable recognition and processing by multiple enzymes from unrelated RiPP pathways. Using this broadly applicable strategy, a thiazoline-forming cyclodehydratase was combined with enzymes from the sactipeptide and lanthipeptide families to create new-to-nature hybrid RiPPs. We also provide insight into design features that enable control over the hybrid biosynthesis to optimize enzyme compatibility and establish a general platform for engineering additional hybrid RiPPs.
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Affiliation(s)
- Brandon
J. Burkhart
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
- Carl
R. Woese Institute for Genomic Biology, University of Illinois at Urbana−Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Nidhi Kakkar
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - Graham A. Hudson
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
| | - Wilfred A. van der Donk
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
- Carl
R. Woese Institute for Genomic Biology, University of Illinois at Urbana−Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, United States
- (W.A.V.) Phone: 1-217-244-5360. Fax: 1-217-244 8533. E-mail:
| | - Douglas A. Mitchell
- Department
of Chemistry, University of Illinois at
Urbana−Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United
States
- Carl
R. Woese Institute for Genomic Biology, University of Illinois at Urbana−Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, United States
- (D.A.M.) Phone: 1-217-333-1345. Fax: 1-217-333-0508. E-mail:
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19
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Mahanta N, Zhang Z, Hudson GA, van der Donk WA, Mitchell DA. Reconstitution and Substrate Specificity of the Radical S-Adenosyl-methionine Thiazole C-Methyltransferase in Thiomuracin Biosynthesis. J Am Chem Soc 2017; 139:4310-4313. [PMID: 28301141 PMCID: PMC5477235 DOI: 10.1021/jacs.7b00693] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Thiomuracin is a thiopeptide antibiotic with potent activity toward Gram-positive drug-resistant bacteria. Thiomuracin is biosynthesized from a precursor peptide, TbtA, by a complex array of posttranslational modifications. One of several intriguing transformations is the C-methylation of thiazole, occurring at an unactivated sp2 carbon. Herein, we report the in vitro reconstitution of TbtI, the responsible radical S-adenosyl-methionine (rSAM) C-methyltransferase, which catalyzes the formation of 5-methylthiazole at a single site. Our studies demonstrate that a linear hexazole-bearing intermediate of TbtA is a substrate for TbtI whereas macrocyclized thiomuracin GZ is not. In determining the minimal substrate for TbtI, we found that the enzyme is functional when most of the leader peptide has been removed. The in vitro reconstitution of TbtI, a class C rSAM methyltransferase, further adds to the chemical versatility of rSAM enzymes, and informs on the complexity of thiomuracin biosynthesis.
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Affiliation(s)
- Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
| | - Zhengan Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Graham A. Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Wilfred A. van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
- Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Douglas A. Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
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20
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Maxson T, Tietz JI, Hudson GA, Guo XR, Tai HC, Mitchell DA. Targeting Reactive Carbonyls for Identifying Natural Products and Their Biosynthetic Origins. J Am Chem Soc 2016; 138:15157-15166. [PMID: 27797509 DOI: 10.1021/jacs.6b06848] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Natural products (NPs) serve important roles as drug candidates and as tools for chemical biology. However, traditional NP discovery, largely based on bioassay-guided approaches, is biased toward abundant compounds and rediscovery rates are high. Orthogonal methods to facilitate discovery of new NPs are thus needed, and herein we describe an isotope tag-based expansion of reactivity-based NP screening to address these shortcomings. Reactivity-based screening is a directed discovery approach in which a specific reactive handle on the NP is targeted by a chemoselective probe to enable its detection by mass spectrometry. In this study, we have developed an aminooxy-containing probe to guide the discovery of aldehyde- and ketone-containing NPs. To facilitate the detection of labeling events, the probe was dibrominated, imparting a unique isotopic signature to distinguish labeled metabolites from spectral noise. As a proof of concept, the probe was then utilized to screen a collection of bacterial extracts, leading to the identification of a new analogue of antipain, deimino-antipain. The bacterial producer of deimino-antipain was sequenced and the responsible biosynthetic gene cluster was identified by bioinformatic analysis and heterologous expression. These data reveal the previously undetermined genetic basis for a well-known family of aldehyde-containing, peptidic protease inhibitors, including antipain, chymostatin, leupeptin, elastatinal, and microbial alkaline protease inhibitor, which have been widely used for over 40 years.
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Affiliation(s)
- Tucker Maxson
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Jonathan I Tietz
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Xiao Rui Guo
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Hua-Chia Tai
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,Department of Microbiology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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21
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Zhang Z, Hudson GA, Mahanta N, Tietz JI, van der Donk WA, Mitchell DA. Biosynthetic Timing and Substrate Specificity for the Thiopeptide Thiomuracin. J Am Chem Soc 2016; 138:15511-15514. [PMID: 27700071 DOI: 10.1021/jacs.6b08987] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The biosynthesis of the thiopeptide thiomuracin is a well-orchestrated process involving a multitude of posttranslational modifications. We show that six Cys residues of a precursor peptide are first cyclodehydrated and oxidized to thiazoles in an ordered, but nonlinear fashion that is leader-peptide-dependent. Then four alcohols are glutamylated and converted to alkenes in a C-to-N terminal directional process that is leader-peptide-independent. Finally, two of these alkenes undergo a formal [4 + 2] cycloaddition to form a trithiazole-substituted pyridine macrocycle. We describe here the factors that govern the substrate specificity and order of biosynthetic events that turn a ribosomal peptide into a powerful antibiotic.
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Affiliation(s)
- Zhengan Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Nilkamal Mahanta
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
| | - Jonathan I Tietz
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
| | - Wilfred A van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, 1206 West Gregory Drive, Urbana, Illinois 61801, USA
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22
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Abstract
![]()
Thiopeptides are potent antibiotics
that inhibit protein synthesis.
They are made by a remarkable post-translational modification process
that transforms a linear peptide into a polycyclic structure. We present
here the in vitro biosynthesis of the core scaffold of thiomuracin
catalyzed by six proteins. We show that cyclodehydration precedes
dehydration, and that dehydration is catalyzed by two proteins in
a tRNAGlu-dependent manner. The enzyme that generates the
pyridine core from two dehydroalanines ejects the leader peptide
as a C-terminal carboxamide. Mutagenesis studies of the enzyme TbtD
identified important residues for a formal [4+2] cycloaddition process.
The core structure of thiomuracin exhibits similar antimicrobial
activity to other known congeners, illustrating that in vitro biosynthesis
is a viable route to potent antibiotics that can be explored for the
rapid and renewable generation of analogues.
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Affiliation(s)
- Graham A Hudson
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Zhengan Zhang
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Jonathan I Tietz
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | - Douglas A Mitchell
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | - Wilfred A van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
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23
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Hudson GA, Bloomingdale RJ, Znosko BM. Thermodynamic contribution and nearest-neighbor parameters of pseudouridine-adenosine base pairs in oligoribonucleotides. RNA 2013; 19:1474-82. [PMID: 24062573 PMCID: PMC3851715 DOI: 10.1261/rna.039610.113] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/22/2013] [Indexed: 05/24/2023]
Abstract
Pseudouridine (Ψ) is the most common noncanonical nucleotide present in naturally occurring RNA and serves a variety of roles in the cell, typically appearing where structural stability is crucial to function. Ψ residues are isomerized from native uridine residues by a class of highly conserved enzymes known as pseudouridine synthases. In order to quantify the thermodynamic impact of pseudouridylation on U-A base pairs, 24 oligoribonucleotides, 16 internal and eight terminal Ψ-A oligoribonucleotides, were thermodynamically characterized via optical melting experiments. The thermodynamic parameters derived from two-state fits were used to generate linearly independent parameters for use in secondary structure prediction algorithms using the nearest-neighbor model. On average, internally pseudouridylated duplexes were 1.7 kcal/mol more stable than their U-A counterparts, and terminally pseudouridylated duplexes were 1.0 kcal/mol more stable than their U-A equivalents. Due to the fact that Ψ-A pairs maintain the same Watson-Crick hydrogen bonding capabilities as the parent U-A pair in A-form RNA, the difference in stability due to pseudouridylation was attributed to two possible sources: the novel hydrogen bonding capabilities of the newly relocated imino group as well as the novel stacking interactions afforded by the electronic configuration of the Ψ residue. The newly derived nearest-neighbor parameters for Ψ-A base pairs may be used in conjunction with other nearest-neighbor parameters for accurately predicting the most likely secondary structure of A-form RNA containing Ψ-A base pairs.
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24
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Hardebeck LKE, Johnson CA, Hudson GA, Ren Y, Watt M, Kirkpatrick CC, Znosko BM, Lewis M. Predicting DNA-intercalator binding: the development of an arene-arene stacking parameter from SAPT analysis of benzene-substituted benzene complexes. J PHYS ORG CHEM 2013. [DOI: 10.1002/poc.3184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Laura K. E. Hardebeck
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Charles A. Johnson
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Graham A. Hudson
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Yi Ren
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Michelle Watt
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Charles C. Kirkpatrick
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Brent M. Znosko
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
| | - Michael Lewis
- Department of Chemistry; Saint Louis University; 3501 Laclede Avenue Saint Louis MO 63103 USA
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Vanegas PL, Hudson GA, Davis AR, Kelly SC, Kirkpatrick CC, Znosko BM. RNA CoSSMos: Characterization of Secondary Structure Motifs--a searchable database of secondary structure motifs in RNA three-dimensional structures. Nucleic Acids Res 2011; 40:D439-44. [PMID: 22127861 PMCID: PMC3245015 DOI: 10.1093/nar/gkr943] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
RNA secondary structure is important for designing therapeutics, understanding protein–RNA binding and predicting tertiary structure of RNA. Several databases and downloadable programs exist that specialize in the three-dimensional (3D) structure of RNA, but none focus specifically on secondary structural motifs such as internal, bulge and hairpin loops. The RNA Characterization of Secondary Structure Motifs (RNA CoSSMos) database is a freely accessible and searchable online database and website of 3D characteristics of secondary structure motifs. To create the RNA CoSSMos database, 2156 Protein Data Bank (PDB) files were searched for internal, bulge and hairpin loops, and each loop's structural information, including sugar pucker, glycosidic linkage, hydrogen bonding patterns and stacking interactions, was included in the database. False positives were defined, identified and reclassified or omitted from the database to ensure the most accurate results possible. Users can search via general PDB information, experimental parameters, sequence and specific motif and by specific structural parameters in the subquery page after the initial search. Returned results for each search can be viewed individually or a complete set can be downloaded into a spreadsheet to allow for easy comparison. The RNA CoSSMos database is automatically updated weekly and is available at http://cossmos.slu.edu.
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Affiliation(s)
- Pamela L Vanegas
- Department of Chemistry, Saint Louis University, Saint Louis, MO 63103, USA
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Gordon CD, Williams SKP, Hudson GA, Stewart J. Factors associated with academic performance of physical therapy students. W INDIAN MED J 2010; 59:203-208. [PMID: 21275127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
UNLABELLED Understanding the pre-matriculation factors that influence academic success facilitates the recruitment and retention of students who are more likely to graduate on time. OBJECTIVE To determine the factors associated with the academic performance of students enrolled in the physical therapy diploma programme. METHODS Records of 250 students enrolled over a twenty-year period at the School of Physical Therapy were reviewed. Data were collected and organized using a data collection sheet. Data were analysed using the Statistical Package for the Social Sciences (SPSS). Relationships between the independent variables: age, gender marital status, work history and entry qualifications, and the dependent variables: academic performance (percentage of subjects passed at the first sitting of examinations and success in the Final Qualifying Examination), withdrawal and delayed graduation were examined using correlation coefficient, t-test, ANOVA and chi-square as appropriate. RESULTS Results revealed that students gaining the minimum entry qualifications at one sitting of GCE O' Level/CXC examinations (p < 0.01) and who had GCE A' Level passes (p < 0.05) were less likely to withdraw from the programme. Students without prior work experience performed better during the course of study (p < 0.05) but the older and married students were more likely to withdraw (p < 0.01). Older students performed better on the Final Qualifying Practical and Theory Examinations taken at the end of the academic programme (p < 0.05) but had a lower percentage of subjects passed at the first sitting of course examinations (p < 0.05). CONCLUSION Students with better academic preparation demonstrated better academic performance. These findings were consistent with prior studies in the field.
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Affiliation(s)
- C D Gordon
- School of Physical Therapy, Department of Basic Medical Sciences, The University of the West Indies, Kingston 7, Jamaica, West Indies
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Wald NJ, Nicolaides-Bouman A, Hudson GA. Plasma retinol, beta-carotene and vitamin E levels in relation to the future risk of breast cancer. Br J Cancer 1988; 57:235. [PMID: 3358917 PMCID: PMC2246433 DOI: 10.1038/bjc.1988.49] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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Barmeir E, Dubowitz B, Hudson GA, Milne FJ, Meyers AM. Radiography of healing dialysis osteodystrophy. Acta Radiol Diagn (Stockh) 1984; 25:107-112. [PMID: 6375266 DOI: 10.1177/028418518402500204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Characteristic skeletal changes of dialysis bone disease associated with multiple fractures were found in ten patients on prolonged regular (high aluminium) haemodialysis. A subsequent prospective investigation with serial radiography demonstrated healing approximately twelve months after a changed treatment regime. The treatment used was deionized or reverse osmosis water dialysis and renal transplantation. The typical osteomalacic and osteosclerotic changes and particularly metaphyseal sclerosis were found to be associated with more rapid clinical healing, whereas secondary hyperparathyroidism indicated delayed healing. It is suggested that plasma aluminium imbalance may lead to disturbance of bone formation with fractures, while healing is associated with normal serum aluminium levels and is manifested radiologically by osteosclerosis, particularly in the metaphyses.
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Abstract
We describe a cellulose sandwich fluoroimmunoassay for Factor VIII-related antigen (FVIIIR:Ag). Plasma is incubated with cellulose-antibody for 2 hours, fluorescent-labelled antiserum is added and the samples are allowed to react for an additional 2 hours. The fluorescence associated with the cellulose-antibody is measured after the tubes have been centrifuged, and the deposit washed and then digested with sodium hydroxide. Ninety-seven samples are assayed and the results are compared with radioimmunoassay (correlation coefficient 0.960) or electroimmunoassay (correlation coefficient 0.882). Between-run coefficients of variation are 8.0% to 9.9%. The cellulose-antibody reagent and the fluorescent-labelled antiserum were both stable over a period of 1 year, demonstrating a major advantage of fluoroimmunoassay over radioimmunoassay.
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Hudson GA, Haddow JE, Ritchie RF. Disparity in antiserum avidity as measured by nephelometry, radial immunodiffusion, and column-binding strength. Clin Chim Acta 1983; 130:239-44. [PMID: 6409453 DOI: 10.1016/0009-8981(83)90121-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
When antiserum potency is being assessed, avidity is often inferred from affinity measurements or from measurements obtained from completely unrelated immunoassay techniques. The present experiments describe an instance where antibodies that have very high column-binding strength, obtained by elution from immobilized antigen with dissociating agents, have low avidity in nephelometry and radial immunodiffusion. This low avidity appears not to be due to molecular damage since the eluted antibodies do not contain molecular aggregates and retain their column-binding strength when reapplied to the immobilized antigen. We theorize that in nephelometry and radial immunodiffusion, lattice formation may require a heterogeneous population of antibodies and that the low avidity fractions may have too limited a specificity. We support this theory by combining two different populations of low avidity antibodies and finding that the combination produces a nephelometric response greater than that of either fraction alone.
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Abstract
We have performed gel acetylcholinesterase analysis blindly on 1,300 consecutive amniotic fluid samples sent to our laboratory for alpha-fetoprotein measurement. Faint acetylcholinesterase bands were identified in nine of 1,300 samples, and all of these were associated with pregnancies free of major fetal malformations. Dense acetylcholinesterase bands were identified in four samples, and all were associated with major fetal malformations. Densitometric analysis of acetylcholinesterase bands provided additional objectivity in classifying band density.
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Milne FJ, Hudson GA, Meyers AM, Baily P, Barmeir E, Dubowitz B, Reis P. Healing of fracturing-bone disease occurring in patients on dialysis. A prospective study. S Afr Med J 1982; 61:955-9. [PMID: 7089762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Ten patients developed fracturing-bone disease (osteomalacia) while on dialysis against water with high levels of aluminium. Eight patients remained on dialysis, using de-ionized or reverse-osmosis water, and 2 received a renal transplant. Clinical improvement as regards bone pain and proximal muscle weakness occurred in 6 months and radiographic evidence of healing of the pseudofractures was seen at approximately 12 months. Associated osteopenia and hyperparathyroidism were found in most patients, but no significant change in either was noted during the study period. The serum parathyroid hormone levels rose significantly in the patients who remained on dialysis. The chest and pelvic deformities typical of healed osteomalacia were seen. This dramatic improvement can only be attributed to the removal of some water-borne element, either by changing the water used in the dialysis or by successful renal transplantation. Aluminium-containing phosphate binders were used throughout the study in the patients on dialysis, and hypophosphataemia was never a feature.
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Brewster TG, Waite DJ, Hudson GA. Quantitation of beta-lipoprotein in cord serum by rate nephelometric immunoassay: a potential screening test for familial hypercholesterolemia. Clin Chem 1982. [DOI: 10.1093/clinchem/28.5.1192] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
We measured beta-lipoprotein in 232 cord sera by rate nephelometry and compared the results with those obtained by electroimmunoassay. The mean (mean +/- two standard deviations) was 544 (293-1009) mg/L by rate nephelometry and 503 (265-955) mg/L by electroimmunoassay. The between-assay correlation coefficient was 0.891. Between-run coefficients of variation were 3.5-4.4% for nephelometry and 11-14% for electroimmunoassay. Nephelometry was faster, more precise, and less labor intensive than electroimmunoassay. For these reasons, rate nephelometry appears to be a more suitable assay system for mass screening, should detection of familial hypercholesterolemia prove feasible and desirable.
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Brewster TG, Waite DJ, Hudson GA. Quantitation of beta-lipoprotein in cord serum by rate nephelometric immunoassay: a potential screening test for familial hypercholesterolemia. Clin Chem 1982; 28:1192-6. [PMID: 7074903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We measured beta-lipoprotein in 232 cord sera by rate nephelometry and compared the results with those obtained by electroimmunoassay. The mean (mean +/- two standard deviations) was 544 (293-1009) mg/L by rate nephelometry and 503 (265-955) mg/L by electroimmunoassay. The between-assay correlation coefficient was 0.891. Between-run coefficients of variation were 3.5-4.4% for nephelometry and 11-14% for electroimmunoassay. Nephelometry was faster, more precise, and less labor intensive than electroimmunoassay. For these reasons, rate nephelometry appears to be a more suitable assay system for mass screening, should detection of familial hypercholesterolemia prove feasible and desirable.
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Hudson GA, Ritchie RF, Haddow JE. Method for testing antiserum titer and avidity in nephelometric systems. Clin Chem 1981; 27:1838-44. [PMID: 6975190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Antiserum performance in a nephelometric system can be characterized by parameters derived from measuring reaction rates. The characterization process is derived from a series of dose-response curves (elicited nephelometric response vs antigen concentration) generated from various dilutions of the antiserum being tested. Antiserum titer can then be calculated by plotting the antigen concentration found at one-half the maximum nephelometric response (Hmax) of each dose-response curve (C50) vs the corresponding antiserum dilution. Antiserum avidity can be calculated by plotting Hmax against its corresponding antiserum concentration. After general expressions are determined for C50 and Hmax vs antiserum concentration, a single dose-response curve suffices for characterizing antisera with respect to titer and avidity. Direct evidence is provided for the validity of C50 and Hmax as measures of titer and avidity by correlating these parameters with antiserum binding strength and with the number of antibodies eluted from immobilized antigen. This method can be applied to evaluate and compare different antiserum lots having the same specificity, to identify reagent inadequacies by comparing antisera of different specificity, and to predict the optimal antiserum dilution to use in performing an assay.
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Abstract
Abstract
Antiserum performance in a nephelometric system can be characterized by parameters derived from measuring reaction rates. The characterization process is derived from a series of dose-response curves (elicited nephelometric response vs antigen concentration) generated from various dilutions of the antiserum being tested. Antiserum titer can then be calculated by plotting the antigen concentration found at one-half the maximum nephelometric response (Hmax) of each dose-response curve (C50) vs the corresponding antiserum dilution. Antiserum avidity can be calculated by plotting Hmax against its corresponding antiserum concentration. After general expressions are determined for C50 and Hmax vs antiserum concentration, a single dose-response curve suffices for characterizing antisera with respect to titer and avidity. Direct evidence is provided for the validity of C50 and Hmax as measures of titer and avidity by correlating these parameters with antiserum binding strength and with the number of antibodies eluted from immobilized antigen. This method can be applied to evaluate and compare different antiserum lots having the same specificity, to identify reagent inadequacies by comparing antisera of different specificity, and to predict the optimal antiserum dilution to use in performing an assay.
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Hudson GA, Milne FJ, Oliver NJ, Reis P, Murray J, Meyers AM. Bone disease in patients on maintenance haemodialysis using softened or de-ionized water. S Afr Med J 1979; 56:439-43. [PMID: 550366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
A clinical, biochemical and radiological study was carried out in 28 patients on maintenance haemodialysis in order to assess the prevalence of bone disease, particularly with regard to osteomalacia and/or osteopenia. The patients were selected from dialysis units using softened or deionized water, and the aluminium levels measured in the different water supplies. The results showed that symptomatic osteomalacia/osteopenia occurs more frequently in the units using softened water, which has a higher aluminium content, than in the de-ionized water unit. The patients dialysed on softened water also have significantly higher serum calcium and phosphorus levels. It is suggested that in Johannesburg, water softening alone is inadequate, and that the high aluminium levels in our water may be responsible for accelerated osteomalacia/osteopenia.
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Brolund GV, Haskins EW, Hudson GA. Calculation of turbidimetric microbiological vitamin assay results, using an APL-360 computer program. J Assoc Off Anal Chem 1973; 56:754-7. [PMID: 4779914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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