1
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Koob T, Döpp S, Schwalbe H. 1H, 13C, 15N and 31P chemical shift assignment of the first stem-loop Guanidine-II riboswitch from Escherichia coli. BIOMOLECULAR NMR ASSIGNMENTS 2025; 19:53-58. [PMID: 39890743 DOI: 10.1007/s12104-025-10217-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2024] [Accepted: 01/09/2025] [Indexed: 02/03/2025]
Abstract
A comprehensive understanding of RNA-based gene regulation is a fundamental aspect for the development of innovative therapeutic options in medicine and for a more targeted response to environmental problems. Within the different mechanisms of RNA-based gene regulation, riboswitches are particularly interesting as they change their structure in response to the interaction with a low molecular weight ligand, often a well-known metabolite. Four distinct classes of riboswitches recognize the very small guanidinium cation. We are focused on the Guanidine-II riboswitch with the mini-ykkC motif. We report here the assignment of the 1H, 13C, 15N and 31P chemical shifts of the 23 nucleotide-long sequence of the first stem-loop of the Guanidine-II riboswitch aptamer from Escherichia coli. Despite its small size, the assignment of the NMR signals of this RNA proved to be challenging as it has symmetrical base pairs and palindromic character.
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Affiliation(s)
- Tatjana Koob
- Institute for Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University Frankfurt, Max‑von‑Laue‑Str. 7, 60438, Frankfurt/M, Germany
- Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Max‑von‑Laue‑Str. 9, 60438, Frankfurt/M, Germany
| | - Silas Döpp
- Institute for Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University Frankfurt, Max‑von‑Laue‑Str. 7, 60438, Frankfurt/M, Germany
- Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Max‑von‑Laue‑Str. 9, 60438, Frankfurt/M, Germany
| | - Harald Schwalbe
- Institute for Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University Frankfurt, Max‑von‑Laue‑Str. 7, 60438, Frankfurt/M, Germany.
- Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Max‑von‑Laue‑Str. 9, 60438, Frankfurt/M, Germany.
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2
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Bowman P, Salvail H. From lab reagent to metabolite: the riboswitch ligand guanidine as a relevant compound in bacterial physiology. J Bacteriol 2025:e0007325. [PMID: 40401924 DOI: 10.1128/jb.00073-25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2025] Open
Abstract
Efforts of the last 20 years in validating novel riboswitches led to the identification of numerous new motifs recognizing compounds with well-established biological functions. However, the recent characterization of widespread classes of riboswitches binding the nitrogen-rich compound guanidine raised questions regarding its physiological significance that has so far remained elusive. Recent findings established that certain bacterial species assimilate guanidine as a nitrogen source via guanidine-specific enzymes and transporters and that complete ammonium oxidizers can use it as a sole source of energy, reductant, and nitrogen. The frequent association of guanidine riboswitches with genes encoding guanidine efflux transporters also hints that bacteria may experience the burden of guanidine as a stressor during their lifestyle. A major gap in understanding the biology of guanidine resides in its natural source. While metabolic pathways responsible for guanidine synthesis were defined in plants, only a few guanidine-producing enzymes have been identified in bacteria, despite indications that the model organism E. coli may produce guanidine. This review summarizes how riboswitch research unveiled guanidine as an important compound in living organisms and the recent findings advancing our knowledge of guanidine biology. We also highlight open questions that will orient future research aiming at gaining further insights into the biological relevance of guanidine.
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Affiliation(s)
- Payton Bowman
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, USA
| | - Hubert Salvail
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, Florida, USA
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3
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Ma X, Gao Z, Niu J, Zhang S, Luo L, Yan S, Zhang Q, Zhang W. Cascade Pd-Catalyzed Azide-Isocyanide Cross Coupling/Cyclization/Lactamization Reactions for the Synthesis of Tricyclic Guanidine-Containing Polyheterocycles. J Org Chem 2025; 90:2707-2716. [PMID: 39932429 DOI: 10.1021/acs.joc.4c02930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2025]
Abstract
A one-pot synthesis of a tricyclic guanidine scaffold is developed. The azido-bearing [3 + 2] adducts are used for cascade azide-isocyanide cross-coupling/nucleophilic cyclization/lactamization to afford highly condensed polyheterocycles. A wide range of azido-containing [3 + 2] adducts and isocyanides are tolerated in the sequential reactions.
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Affiliation(s)
- Xiaoming Ma
- School of Pharmacy, Changzhou University, 1 Gehu Road, Changzhou 213164, China
| | - Zijie Gao
- School of Pharmacy, Changzhou University, 1 Gehu Road, Changzhou 213164, China
| | - Jiawei Niu
- School of Pharmacy, Changzhou University, 1 Gehu Road, Changzhou 213164, China
| | - Sai Zhang
- School of Pharmacy, Changzhou University, 1 Gehu Road, Changzhou 213164, China
| | - Lingfeng Luo
- School of Pharmacy, Changzhou University, 1 Gehu Road, Changzhou 213164, China
| | - Shenghu Yan
- School of Pharmacy, Changzhou University, 1 Gehu Road, Changzhou 213164, China
| | - Qiang Zhang
- School of Chemistry and Life Sciences, Suzhou University of Science and Technology, 99 Xuefu Road, Suzhou 215009, China
| | - Wei Zhang
- Department of Chemistry and Center for Green Chemistry, University of Massachusetts Boston, 100 Morrissey Blvd, Boston, Massachusetts 02125, United States
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4
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Wissbroecker KB, Zmuda AJ, Karumanchi H, Niehaus TD. Biochemical and genomic evidence for converging metabolic routes of metformin and biguanide breakdown in environmental Pseudomonads. J Biol Chem 2024; 300:107935. [PMID: 39476966 DOI: 10.1016/j.jbc.2024.107935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2024] [Revised: 10/18/2024] [Accepted: 10/21/2024] [Indexed: 12/01/2024] Open
Abstract
Metformin is commonly used to lower blood glucose levels and is one of the most widely used pharmaceuticals worldwide. Typical doses are high (0.5-2.0 g day-1) and the majority travels through the digestive system unabsorbed and enters the wastewater system. Metformin is not removed by standard wastewater treatments and eventually enters freshwater systems, where it can form N-chloro-derivatives that are toxic to fish and human cells. Thus, metformin is one of the most prevalent anthropogenic pollutants worldwide and there has been considerable interest in finding ways to remove it. We recently isolated Pseudomonads capable of growing on metformin as the sole nitrogen source. We identified candidate genes involved in metformin breakdown through genomic analyses informed by feeding studies. One candidate, a pair of genes that are located on ∼80kb extra-genomic plasmids, was shown to encode a heteromeric Ni-dependent hydrolase that converts metformin to guanylurea and dimethylamine. Metforminase activity of these gene products is now well established as our results confirm three recently published independent studies. Our isolated Pseudomonads also grow on biguanide, suggesting the existence of an additional breakdown enzyme. Another candidate gene located on the ∼80kb plasmids was shown to encode an aminohydrolase that converts biguanide to guanylurea. Biguanide may arise through successive N-demethylations of metformin or come from other sources. Our results suggest that the recent evolution of metforminase and biguanide hydrolase enzymes allow Pseudomonads to convert either metformin or biguanide to guanylurea, which can be assimilated by existing pathways.
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Affiliation(s)
- Katie B Wissbroecker
- The Department of Plant and Microbial Biology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Anthony J Zmuda
- The Department of Plant and Microbial Biology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Harsheeth Karumanchi
- The Department of Plant and Microbial Biology, University of Minnesota, Minneapolis, Minnesota, USA
| | - Thomas D Niehaus
- The Department of Plant and Microbial Biology, University of Minnesota, Minneapolis, Minnesota, USA.
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5
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Sinn M, Riede L, Fleming JR, Funck D, Lutz H, Bachmann A, Mayans O, Hartig JS. Metformin hydrolase is a recently evolved nickel-dependent heteromeric ureohydrolase. Nat Commun 2024; 15:8045. [PMID: 39271653 PMCID: PMC11399263 DOI: 10.1038/s41467-024-51752-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 08/16/2024] [Indexed: 09/15/2024] Open
Abstract
The anti-diabetic drug metformin is one of the most widely prescribed medicines in the world. Together with its degradation product guanylurea, it is a major pharmaceutical pollutant in wastewater treatment plants and surface waters. An operon comprising two genes of the ureohydrolase family in Pseudomonas and Aminobacter species has recently been implicated in metformin degradation. However, the corresponding proteins have not been characterized. Here we show that these genes encode a Ni2+-dependent enzyme that efficiently and specifically hydrolyzes metformin to guanylurea and dimethylamine. The active enzyme is a heteromeric complex of α- and β- subunits in which only the α-subunits contain the conserved His and Asp residues for the coordination of two Ni2+ ions in the active site. A crystal structure of metformin hydrolase reveals an α2β4 stoichiometry of the hexameric complex, which is unprecedented in the ureohydrolase family. By studying a closely related but more widely distributed enzyme, we find that the putative predecessor specifically hydrolyzes dimethylguanidine instead of metformin. Our findings establish the molecular basis for metformin hydrolysis to guanylurea as the primary pathway for metformin biodegradation and provide insight into the recent evolution of ureohydrolase family proteins in response to an anthropogenic compound.
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Affiliation(s)
- M Sinn
- Department of Chemistry, University of Konstanz, Konstanz, Germany.
| | - L Riede
- Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - J R Fleming
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - D Funck
- Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - H Lutz
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - A Bachmann
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - O Mayans
- Department of Biology, University of Konstanz, Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany
| | - J S Hartig
- Department of Chemistry, University of Konstanz, Konstanz, Germany.
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany.
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6
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Palatinszky M, Herbold CW, Sedlacek CJ, Pühringer D, Kitzinger K, Giguere AT, Wasmund K, Nielsen PH, Dueholm MKD, Jehmlich N, Gruseck R, Legin A, Kostan J, Krasnici N, Schreiner C, Palmetzhofer J, Hofmann T, Zumstein M, Djinović-Carugo K, Daims H, Wagner M. Growth of complete ammonia oxidizers on guanidine. Nature 2024; 633:646-653. [PMID: 39143220 PMCID: PMC11410670 DOI: 10.1038/s41586-024-07832-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 07/15/2024] [Indexed: 08/16/2024]
Abstract
Guanidine is a chemically stable nitrogen compound that is excreted in human urine and is widely used in manufacturing of plastics, as a flame retardant and as a component of propellants, and is well known as a protein denaturant in biochemistry1-3. Guanidine occurs widely in nature and is used by several microorganisms as a nitrogen source, but microorganisms growing on guanidine as the only substrate have not yet been identified. Here we show that the complete ammonia oxidizer (comammox) Nitrospira inopinata and probably most other comammox microorganisms can grow on guanidine as the sole source of energy, reductant and nitrogen. Proteomics, enzyme kinetics and the crystal structure of a N. inopinata guanidinase homologue demonstrated that it is a bona fide guanidinase. Incubation experiments with comammox-containing agricultural soil and wastewater treatment plant microbiomes suggested that guanidine serves as substrate for nitrification in the environment. The identification of guanidine as a growth substrate for comammox shows an unexpected niche of these globally important nitrifiers and offers opportunities for their isolation.
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Affiliation(s)
- Marton Palatinszky
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Craig W Herbold
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Te Kura Pūtaiao Koiora (School of Biological Sciences), Te Whare Wānanga o Waitaha (University of Canterbury), Ōtautahi (Christchurch), Aotearoa New Zealand
| | - Christopher J Sedlacek
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Dominic Pühringer
- Department of Structural and Computational Biology, Center for Molecular Biology, University of Vienna, Vienna, Austria
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
| | - Katharina Kitzinger
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Andrew T Giguere
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Kenneth Wasmund
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
- School of Biological Sciences, University of Portsmouth, Portsmouth, UK
| | - Per H Nielsen
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Morten K D Dueholm
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Nico Jehmlich
- Helmholtz-Centre for Environmental Research-UFZ, Department of Molecular Systems Biology, Leipzig, Germany
| | - Richard Gruseck
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Doctoral School in Microbiology and Environmental Science, University of Vienna, Vienna, Austria
| | - Anton Legin
- Institute of Inorganic Chemistry, Faculty of Chemistry, University of Vienna, Vienna, Austria
| | - Julius Kostan
- Department of Structural and Computational Biology, Center for Molecular Biology, University of Vienna, Vienna, Austria
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
| | - Nesrete Krasnici
- Department of Structural and Computational Biology, Center for Molecular Biology, University of Vienna, Vienna, Austria
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
| | - Claudia Schreiner
- Department of Structural and Computational Biology, Center for Molecular Biology, University of Vienna, Vienna, Austria
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
| | - Johanna Palmetzhofer
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- Doctoral School in Microbiology and Environmental Science, University of Vienna, Vienna, Austria
| | - Thilo Hofmann
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Michael Zumstein
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Center for Molecular Biology, University of Vienna, Vienna, Austria
- Max Perutz Labs, Vienna Biocenter Campus (VBC), Vienna, Austria
- The Comammox Research Platform, University of Vienna, Vienna, Austria
- European Molecular Biology Laboratory (EMBL), Grenoble, France
| | - Holger Daims
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
- The Comammox Research Platform, University of Vienna, Vienna, Austria
| | - Michael Wagner
- Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
- The Comammox Research Platform, University of Vienna, Vienna, Austria.
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7
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Steuer J, Sinn M, Eble F, Rütschlin S, Böttcher T, Hartig JS, Peter C. Cooperative binding of bivalent ligands yields new insights into the guanidine-II riboswitch. NAR Genom Bioinform 2024; 6:lqae132. [PMID: 39323654 PMCID: PMC11423145 DOI: 10.1093/nargab/lqae132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 08/23/2024] [Accepted: 09/12/2024] [Indexed: 09/27/2024] Open
Abstract
Riboswitches are involved in regulating the gene expression in bacteria. They are located within the untranslated regions of bacterial messenger RNA and function as switches by adjusting their shape, depending on the presence or absence of specific ligands. To decipher the fundamental aspects of bacterial gene control, it is therefore important to understand the mechanisms that underlie these conformational switches. To this end, a combination of an experimental binding study, molecular simulations and machine learning has been employed to obtain insights into the conformational changes and structural dynamics of the guanidine-II riboswitch. By exploiting the design of a bivalent ligand, we were able to study ligand binding in the aptamer dimer at the molecular level. Spontaneous ligand-binding events, which are usually difficult to simulate, were observed and the contributing factors are described. These findings were further confirmed by in vivo experiments, where the cooperative binding effects of the bivalent ligands resulted in increased binding affinity compared to the native guanidinium ligand. Beyond ligand binding itself, the simulations revealed a novel, ligand-dependent base-stacking interaction outside of the binding pocket that stabilizes the riboswitch.
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Affiliation(s)
- Jakob Steuer
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, 78457 Konstanz, Germany
| | - Malte Sinn
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Franziska Eble
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
| | - Sina Rütschlin
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, 78457 Konstanz, Germany
| | - Thomas Böttcher
- Faculty of Chemistry, Institute for Biological Chemistry & Centre for Microbiology and Environmental Systems Science, Department of Microbiology and Ecosystems Science, University of Vienna, Josef-Holaubek-Platz 2 (UZA II), 1090 Vienna, Austria
| | - Jörg S Hartig
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, 78457 Konstanz, Germany
| | - Christine Peter
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, 78457 Konstanz, Germany
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8
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Funck D, Sinn M, Forlani G, Hartig JS. Guanidine production by plant homoarginine-6-hydroxylases. eLife 2024; 12:RP91458. [PMID: 38619227 PMCID: PMC11018352 DOI: 10.7554/elife.91458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024] Open
Abstract
Metabolism and biological functions of the nitrogen-rich compound guanidine have long been neglected. The discovery of four classes of guanidine-sensing riboswitches and two pathways for guanidine degradation in bacteria hint at widespread sources of unconjugated guanidine in nature. So far, only three enzymes from a narrow range of bacteria and fungi have been shown to produce guanidine, with the ethylene-forming enzyme (EFE) as the most prominent example. Here, we show that a related class of Fe2+- and 2-oxoglutarate-dependent dioxygenases (2-ODD-C23) highly conserved among plants and algae catalyze the hydroxylation of homoarginine at the C6-position. Spontaneous decay of 6-hydroxyhomoarginine yields guanidine and 2-aminoadipate-6-semialdehyde. The latter can be reduced to pipecolate by pyrroline-5-carboxylate reductase but more likely is oxidized to aminoadipate by aldehyde dehydrogenase ALDH7B in vivo. Arabidopsis has three 2-ODD-C23 isoforms, among which Din11 is unusual because it also accepted arginine as substrate, which was not the case for the other 2-ODD-C23 isoforms from Arabidopsis or other plants. In contrast to EFE, none of the three Arabidopsis enzymes produced ethylene. Guanidine contents were typically between 10 and 20 nmol*(g fresh weight)-1 in Arabidopsis but increased to 100 or 300 nmol*(g fresh weight)-1 after homoarginine feeding or treatment with Din11-inducing methyljasmonate, respectively. In 2-ODD-C23 triple mutants, the guanidine content was strongly reduced, whereas it increased in overexpression plants. We discuss the implications of the finding of widespread guanidine-producing enzymes in photosynthetic eukaryotes as a so far underestimated branch of the bio-geochemical nitrogen cycle and propose possible functions of natural guanidine production.
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Affiliation(s)
- Dietmar Funck
- Department of Chemistry, University of KonstanzKonstanzGermany
| | - Malte Sinn
- Department of Chemistry, University of KonstanzKonstanzGermany
| | - Giuseppe Forlani
- Department of Life Science and Biotechnology, University of FerraraFerraraItaly
| | - Jörg S Hartig
- Department of Chemistry, University of KonstanzKonstanzGermany
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9
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Lucero RM, Demirer K, Yeh TJ, Stockbridge RB. Transport of metformin metabolites by guanidinium exporters of the small multidrug resistance family. J Gen Physiol 2024; 156:e202313464. [PMID: 38294434 PMCID: PMC10829512 DOI: 10.1085/jgp.202313464] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 12/01/2023] [Accepted: 01/04/2024] [Indexed: 02/01/2024] Open
Abstract
Proteins from the small multidrug resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in the metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMRGdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea. We use solid-supported membrane electrophysiology to evaluate the transport kinetics for guanylurea and native substrate guanidinium by four representative SMRGdx homologs. Using an internal reference to normalize independent electrophysiology experiments, we show that transport rates are comparable for genomic and plasmid-associated SMRGdx homologs, and using a proteoliposome-based transport assay, we show that 2 proton:1 substrate transport stoichiometry is maintained. Additional characterization of guanidinium and guanylurea export properties focuses on the structurally characterized homolog, Gdx-Clo, for which we examined the pH dependence and thermodynamics of substrate binding and solved an x-ray crystal structure with guanylurea bound. Together, these experiments contribute in two main ways. By providing the first detailed kinetic examination of the structurally characterized SMRGdx homolog Gdx-Clo, they provide a functional framework that will inform future mechanistic studies of this model transport protein. Second, this study casts light on a potential role for SMRGdx transporters in microbial handling of metformin and its microbial metabolic byproducts, providing insight into how native transport physiologies are co-opted to contend with new selective pressures.
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Affiliation(s)
- Rachael M. Lucero
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
| | - Kemal Demirer
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | | | - Randy B. Stockbridge
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Program in Biophysics, University of Michigan, Ann Arbor, MI, USA
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10
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Rubin-Blum M, Yudkovsky Y, Marmen S, Raveh O, Amrani A, Kutuzov I, Guy-Haim T, Rahav E. Tar patties are hotspots of hydrocarbon turnover and nitrogen fixation during a nearshore pollution event in the oligotrophic southeastern Mediterranean Sea. MARINE POLLUTION BULLETIN 2023; 197:115747. [PMID: 37995430 DOI: 10.1016/j.marpolbul.2023.115747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 10/29/2023] [Accepted: 11/01/2023] [Indexed: 11/25/2023]
Abstract
Weathered oil, that is, tar, forms hotspots of hydrocarbon degradation by complex biota in marine environment. Here, we used marker gene sequencing and metagenomics to characterize the communities of bacteria, archaea and eukaryotes that colonized tar patties and control samples (wood, plastic), collected in the littoral following an offshore spill in the warm, oligotrophic southeastern Mediterranean Sea (SEMS). We show potential aerobic and anaerobic hydrocarbon catabolism niches on tar interior and exterior, linking carbon, sulfur and nitrogen cycles. Alongside aromatics and larger alkanes, short-chain alkanes appear to fuel dominant populations, both the aerobic clade UBA5335 (Macondimonas), anaerobic Syntropharchaeales, and facultative Mycobacteriales. Most key organisms, including the hydrocarbon degraders and cyanobacteria, have the potential to fix dinitrogen, potentially alleviating the nitrogen limitation of hydrocarbon degradation in the SEMS. We highlight the complexity of these tar-associated communities, where bacteria, archaea and eukaryotes co-exist, likely exchanging metabolites and competing for resources and space.
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Affiliation(s)
- Maxim Rubin-Blum
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel.
| | - Yana Yudkovsky
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
| | - Sophi Marmen
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
| | - Ofrat Raveh
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
| | - Alon Amrani
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Ilya Kutuzov
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Tamar Guy-Haim
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
| | - Eyal Rahav
- Israel Oceanographic and Limnological Research, National Institute of Oceanography, Haifa, Israel
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11
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Lucero RM, Demirer K, Yeh TJ, Stockbridge RB. Transport of metformin metabolites by guanidinium exporters of the Small Multidrug Resistance family. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.552832. [PMID: 37645731 PMCID: PMC10461911 DOI: 10.1101/2023.08.10.552832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Proteins from the Small Multidrug Resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMRGdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea. We use solid supported membrane electrophysiology to evaluate the transport kinetics for guanylurea and native substrate guanidinium by four representative SMRGdx homologues. Using an internal reference to normalize independent electrophysiology experiments, we show that transport rates are comparable for genomic and plasmid-associated SMRGdx homologues, and using a proteoliposome-based transport assay, we show that 2 proton:1 substrate transport stoichiometry is maintained. Additional characterization of guanidinium and guanylurea export properties focuses on the structurally characterized homologue, Gdx-Clo, for which we examined the pH dependence and thermodynamics of substrate binding and solved an x-ray crystal structure with guanylurea bound. Together, these experiments contribute in two main ways. By providing the first detailed kinetic examination of the structurally characterized SMRGdx homologue Gdx-Clo, they provide a functional framework that will inform future mechanistic studies of this model transport protein. Second, this study casts light on a potential role for SMRGdx transporters in microbial handling of metformin and its microbial metabolic byproducts, providing insight into how native transport physiologies are co-opted to contend with new selective pressures.
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Affiliation(s)
| | - Kemal Demirer
- Department of Molecular, Cellular, and Developmental Biology
| | - Trevor Justin Yeh
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Randy B Stockbridge
- Program in Chemical Biology
- Department of Molecular, Cellular, and Developmental Biology
- Program in Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
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12
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Hauth F, Funck D, Hartig JS. A standalone editing protein deacylates mischarged canavanyl-tRNAArg to prevent canavanine incorporation into proteins. Nucleic Acids Res 2023; 51:2001-2010. [PMID: 36626933 PMCID: PMC10018355 DOI: 10.1093/nar/gkac1197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/16/2022] [Accepted: 12/06/2022] [Indexed: 01/12/2023] Open
Abstract
Error-free translation of the genetic code into proteins is vitally important for all organisms. Therefore, it is crucial that the correct amino acids are loaded onto their corresponding tRNAs. This process is highly challenging when aminoacyl-tRNA-synthetases encounter structural analogues to the native substrate like the arginine antimetabolite canavanine. To circumvent deleterious incorporation due to tRNA mischarging, editing mechanisms have evolved. However, only for half of the tRNA synthetases, editing activity is known and only few specific standalone editing proteins have been described. Understanding the diverse mechanisms resulting in error-free protein synthesis is of great importance. Here, we report the discovery of a protein that is upregulated upon canavanine stimulation in bacteria that live associated with canavanine-producing plants. We demonstrate that it acts as standalone editing protein specifically deacylating canavanylated tRNAArg. We therefore propose canavanyl-tRNAArgdeacylase (CtdA) as systematic name. Knockout strains show severe growth defects in canavanine-containing media and incorporate high amounts of canavanine into the proteome. CtdA is frequently found under control of guanidine riboswitches, revealing a functional connection of canavanine and guanidine metabolisms. Our results are the first to show editing activity towards mischarged tRNAArg and add to the puzzle of how faithful translation is ensured in nature.
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Affiliation(s)
- Franziskus Hauth
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Dietmar Funck
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Jörg S Hartig
- To whom correspondence should be addressed. Tel: +49 7531 88 4575;
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13
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Serrano-Gutiérrez M, Merino E. Antisense-acting riboswitches: A poorly characterized yet important model of transcriptional regulation in prokaryotic organisms. PLoS One 2023; 18:e0281744. [PMID: 36809273 PMCID: PMC9943018 DOI: 10.1371/journal.pone.0281744] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 01/30/2023] [Indexed: 02/23/2023] Open
Abstract
Riboswitches are RNA elements involved in regulating genes that participate in the biosynthesis or transport of essential metabolites. They are characterized by their ability to recognize their target molecules with high affinity and specificity. Riboswitches are commonly cotranscribed with their target genes and are located at the 5' end of their transcriptional units. To date, only two exceptional cases of riboswitches being situated at the 3' end and transcribing in the antisense direction of their regulated genes have been described. The first case involves a SAM riboswitch located at the 3' end of the ubiG-mccB-mccA operon in Clostridium acetobutylicum involved in converting methionine to cysteine. The second case concerns a Cobalamin riboswitch in Listeria monocytogenes that regulates the transcription factor PocR related to this organism's pathogenic process. In almost a decade since the first descriptions of antisense-acting riboswitches, no new examples have been described. In this work, we performed a computational analysis to identify new examples of antisense-acting riboswitches. We found 292 cases in which, according to the available information, we infer that the expected regulation of the riboswitch is consistent with the signaling molecule it senses and the metabolic function of the regulated gene. The metabolic implications of this novel type of regulation are thoroughly discussed.
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Affiliation(s)
- Mariela Serrano-Gutiérrez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Enrique Merino
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- * E-mail:
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14
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Lenkeit F, Eckert I, Sinn M, Hauth F, Hartig JS, Weinberg Z. A variant of guanidine-IV riboswitches exhibits evidence of a distinct ligand specificity. RNA Biol 2023; 20:10-19. [PMID: 36548032 PMCID: PMC9788692 DOI: 10.1080/15476286.2022.2160562] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Riboswitches are regulatory RNAs that specifically bind a small molecule or ion. Like metabolite-binding proteins, riboswitches can evolve new ligand specificities, and some examples of this phenomenon have been validated. As part of work based on comparative genomics to discover novel riboswitches, we encountered a candidate riboswitch with striking similarities to the recently identified guanidine-IV riboswitch. This candidate riboswitch, the Gd4v motif, is predicted in four distinct bacterial phyla, thus almost as widespread as the guanidine-IV riboswitch. Bioinformatic and experimental analysis suggest that the Gd4v motif is a riboswitch that binds a ligand other than guanidine. It is found associated with gene classes that differ from genes regulated by confirmed guanidine riboswitches. In inline-probing assays, we showed that free guanidine binds only weakly to one of the tested sequences of the variant. Further tested compounds did not show binding, attenuation of transcription termination, or activation of a genetic reporter construct. We characterized an N-acetyltransferase frequently associated with the Gd4v motif and compared its substrate preference to an N-acetyltransferase that occurs under control of guanidine-IV riboswitches. The substrates of this Gd4v-motif-associated enzyme did not show activity for Gd4v RNA binding or transcription termination. Hence, the ligand of the candidate riboswitch motif remains unidentified. The variant RNA motif is predominantly found in gut metagenome sequences, hinting at a ligand that is highly relevant in this environment. This finding is a first step to determining the identity of this unknown ligand, and understanding how guanidine-IV-riboswitch-like structures can evolve to bind different ligands.
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Affiliation(s)
- Felina Lenkeit
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany
| | - Iris Eckert
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107Leipzig, Germany
| | - Malte Sinn
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany
| | - Franziskus Hauth
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany
| | - Jörg S. Hartig
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457Konstanz, Germany,CONTACT Jörg S. Hartig
| | - Zasha Weinberg
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107Leipzig, Germany,Zasha Weinberg Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107Leipzig, Germany
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15
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Burata OE, Yeh TJ, Macdonald CB, Stockbridge RB. Still rocking in the structural era: A molecular overview of the small multidrug resistance (SMR) transporter family. J Biol Chem 2022; 298:102482. [PMID: 36100040 PMCID: PMC9574504 DOI: 10.1016/j.jbc.2022.102482] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 08/24/2022] [Accepted: 09/07/2022] [Indexed: 11/20/2022] Open
Abstract
The small multidrug resistance (SMR) family is composed of widespread microbial membrane proteins that fulfill different transport functions. Four functional SMR subtypes have been identified, which variously transport the small, charged metabolite guanidinium, bulky hydrophobic drugs and antiseptics, polyamines, and glycolipids across the membrane bilayer. The transporters possess a minimalist architecture, with ∼100-residue subunits that require assembly into homodimers or heterodimers for transport. In part because of their simple construction, the SMRs are a tractable system for biochemical and biophysical analysis. Studies of SMR transporters over the last 25 years have yielded deep insights for diverse fields, including membrane protein topology and evolution, mechanisms of membrane transport, and bacterial multidrug resistance. Here, we review recent advances in understanding the structures and functions of SMR transporters. New molecular structures of SMRs representing two of the four functional subtypes reveal the conserved structural features that have permitted the emergence of disparate substrate transport functions in the SMR family and illuminate structural similarities with a distantly related membrane transporter family, SLC35/DMT.
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Affiliation(s)
- Olive E Burata
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Trevor Justin Yeh
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Randy B Stockbridge
- Program in Chemical Biology, University of Michigan, Ann Arbor, Michigan, USA; Program in Biophysics, University of Michigan, Ann Arbor, Michigan, USA; Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA.
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16
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Funck D, Sinn M, Fleming JR, Stanoppi M, Dietrich J, López-Igual R, Mayans O, Hartig JS. Discovery of a Ni 2+-dependent guanidine hydrolase in bacteria. Nature 2022; 603:515-521. [PMID: 35264792 DOI: 10.1038/s41586-022-04490-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 01/31/2022] [Indexed: 12/14/2022]
Abstract
Nitrogen availability is a growth-limiting factor in many habitats1, and the global nitrogen cycle involves prokaryotes and eukaryotes competing for this precious resource. Only some bacteria and archaea can fix elementary nitrogen; all other organisms depend on the assimilation of mineral or organic nitrogen. The nitrogen-rich compound guanidine occurs widely in nature2-4, but its utilization is impeded by pronounced resonance stabilization5, and enzymes catalysing hydrolysis of free guanidine have not been identified. Here we describe the arginase family protein GdmH (Sll1077) from Synechocystis sp. PCC 6803 as a Ni2+-dependent guanidine hydrolase. GdmH is highly specific for free guanidine. Its activity depends on two accessory proteins that load Ni2+ instead of the typical Mn2+ ions into the active site. Crystal structures of GdmH show coordination of the dinuclear metal cluster in a geometry typical for arginase family enzymes and allow modelling of the bound substrate. A unique amino-terminal extension and a tryptophan residue narrow the substrate-binding pocket and identify homologous proteins in further cyanobacteria, several other bacterial taxa and heterokont algae as probable guanidine hydrolases. This broad distribution suggests notable ecological relevance of guanidine hydrolysis in aquatic habitats.
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Affiliation(s)
- D Funck
- Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - M Sinn
- Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - J R Fleming
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - M Stanoppi
- Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - J Dietrich
- Department of Chemistry, University of Konstanz, Konstanz, Germany
| | - R López-Igual
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and C.S.I.C, Seville, Spain
| | - O Mayans
- Department of Biology, University of Konstanz, Konstanz, Germany.,Konstanz Graduate School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany
| | - J S Hartig
- Department of Chemistry, University of Konstanz, Konstanz, Germany. .,Konstanz Graduate School Chemical Biology (KoRS-CB), University of Konstanz, Konstanz, Germany.
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17
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Schamber T, Binas O, Schlundt A, Wacker A, Schwalbe H. Characterization of Structure and Dynamics of the Guanidine-II Riboswitch from Escherichia coli by NMR Spectroscopy and Small-Angle X-ray Scattering (SAXS). Chembiochem 2022; 23:e202100564. [PMID: 34847270 PMCID: PMC9300104 DOI: 10.1002/cbic.202100564] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/30/2021] [Indexed: 11/12/2022]
Abstract
Riboswitches are regulatory RNA elements that undergo functionally important allosteric conformational switching upon binding of specific ligands. The here investigated guanidine-II riboswitch binds the small cation, guanidinium, and forms a kissing loop-loop interaction between its P1 and P2 hairpins. We investigated the structural changes to support previous studies regarding the binding mechanism. Using NMR spectroscopy, we confirmed the structure as observed in crystal structures and we characterized the kissing loop interaction upon addition of Mg2+ and ligand for the riboswitch aptamer from Escherichia coli. We further investigated closely related mutant constructs providing further insight into functional differences between the two (different) hairpins P1 and P2. Formation of intermolecular interactions were probed by small-angle X-ray scattering (SAXS) and NMR DOSY data. All data are consistent and show the formation of oligomeric states of the riboswitch induced by Mg2+ and ligand binding.
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Affiliation(s)
- Tatjana Schamber
- Institute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 760438Frankfurt/MainGermany
- Center for Biomolecular Magnetic ResonanceInstitute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 7–960438Frankfurt/MainGermany
| | - Oliver Binas
- Institute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 760438Frankfurt/MainGermany
- Center for Biomolecular Magnetic ResonanceInstitute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 7–960438Frankfurt/MainGermany
| | - Andreas Schlundt
- Institute for Molecular BiosciencesJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 960438Frankfurt/MainGermany
- Center for Biomolecular Magnetic ResonanceInstitute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 7–960438Frankfurt/MainGermany
| | - Anna Wacker
- Institute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 760438Frankfurt/MainGermany
- Center for Biomolecular Magnetic ResonanceInstitute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 7–960438Frankfurt/MainGermany
| | - Harald Schwalbe
- Institute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 760438Frankfurt/MainGermany
- Center for Biomolecular Magnetic ResonanceInstitute for Organic Chemistry and Chemical BiologyJohann Wolfgang Goethe UniversityMax-von-Laue-Str. 7–960438Frankfurt/MainGermany
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18
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Abstract
More than 55 distinct classes of riboswitches that respond to small metabolites or elemental ions have been experimentally validated to date. The ligands sensed by these riboswitches are biased in favor of fundamental compounds or ions that are likely to have been relevant to ancient forms of life, including those that might have populated the "RNA World", which is a proposed biochemical era that predates the evolutionary emergence of DNA and proteins. In the following text, I discuss the various types of ligands sensed by some of the most common riboswitches present in modern bacterial cells and consider implications for ancient biological processes centered on the proven capabilities of these RNA-based sensors. Although most major biochemical aspects of metabolism are represented by known riboswitch classes, there are striking sensory gaps in some key areas. These gaps could reveal weaknesses in the performance capabilities of RNA that might have hampered RNA World evolution, or these could highlight opportunities to discover additional riboswitch classes that sense essential metabolites.
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Affiliation(s)
- Ronald R. Breaker
- Corresponding Author: Ronald R. Breaker - Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103, United States; Phone: 203-432-9389; , Twitter: @RonBreaker
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19
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Hauth F, Buck H, Stanoppi M, Hartig JS. Canavanine utilization via homoserine and hydroxyguanidine by a PLP-dependent γ-lyase in Pseudomonadaceae and Rhizobiales. RSC Chem Biol 2022; 3:1240-1250. [PMID: 36320885 PMCID: PMC9533460 DOI: 10.1039/d2cb00128d] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 08/18/2022] [Indexed: 12/02/2022] Open
Abstract
Canavanine, the δ-oxa-analogue of arginine, is produced as one of the main nitrogen storage compounds in legume seeds and has repellent properties. Its toxicity originates from incorporation into proteins as well as arginase-mediated hydrolysis to canaline that forms stable oximes with carbonyls. So far no pathway or enzyme has been identified acting specifically on canavanine. Here we report the characterization of a novel PLP-dependent enzyme, canavanine-γ-lyase, that catalyzes the elimination of hydroxyguanidine from canavanine to subsequently yield homoserine. Homoserine-dehydrogenase, aspartate–semialdehyde–dehydrogenase and ammonium–aspartate–lyase activities are also induced for facilitating canavanine utilization. We demonstrate that this novel pathway is found in certain Pseudomonas species and the Rhizobiales symbionts of legumes. The findings broaden the diverse reactions that the versatile class of PLP-dependent enzymes is able to catalyze. Since canavanine utilization is found prominently in root-associated bacteria, it could have important implications for the establishment and maintenance of the legume rhizosphere. A novel degradation pathway enables rhizosphere-associated bacteria to utilize canavanine.![]()
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Affiliation(s)
- Franziskus Hauth
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Hiltrun Buck
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Marco Stanoppi
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
| | - Jörg S. Hartig
- Department of Chemistry, University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
- Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, 78457 Konstanz, Germany
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