1
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Srinivasan K, Banerjee A, Sengupta J. Cryo-EM structures reveal the molecular mechanism of HflX-mediated erythromycin resistance in mycobacteria. Structure 2024:S0969-2126(24)00234-X. [PMID: 39029461 DOI: 10.1016/j.str.2024.06.016] [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: 02/05/2024] [Revised: 05/07/2024] [Accepted: 06/23/2024] [Indexed: 07/21/2024]
Abstract
Mycobacterial HflX confers resistance against macrolide antibiotics. However, the exact molecular mechanism is poorly understood. To gain further insights, we determined the cryo-EM structures of M. smegmatis (Msm) HflX-50S subunit and 50S subunit-erythromycin (ERY) complexes at a global resolution of approximately 3 Å. A conserved nucleotide A2286 at the gate of nascent peptide exit tunnel (NPET) adopts a swayed conformation in HflX-50S complex and interacts with a loop within the linker helical (LH) domain of MsmHflX that contains an additional 9 residues insertion. Interestingly, the swaying of this nucleotide, which is usually found in the non-swayed conformation, is induced by erythromycin binding. Furthermore, we observed that erythromycin decreases HflX's ribosome-dependent GTP hydrolysis, resulting in its enhanced binding and anti-association activity on the 50S subunit. Our findings reveal how mycobacterial HflX senses the presence of macrolides at the peptide tunnel entrance and confers antibiotic resistance in mycobacteria.
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Affiliation(s)
- Krishnamoorthi Srinivasan
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Aneek Banerjee
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Jayati Sengupta
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
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2
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Koli S, Shetty S. Ribosomal dormancy at the nexus of ribosome homeostasis and protein synthesis. Bioessays 2024; 46:e2300247. [PMID: 38769702 DOI: 10.1002/bies.202300247] [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: 12/28/2023] [Revised: 02/05/2024] [Accepted: 05/02/2024] [Indexed: 05/22/2024]
Abstract
Dormancy or hibernation is a non-proliferative state of cells with low metabolic activity and gene expression. Dormant cells sequester ribosomes in a translationally inactive state, called dormant/hibernating ribosomes. These dormant ribosomes are important for the preservation of ribosomes and translation shut-off. While recent studies attempted to elucidate their modes of formation, the regulation and roles of the diverse dormant ribosomal populations are still largely understudied. The mechanistic details of the formation of dormant ribosomes in stress and especially their disassembly during recovery remain elusive. In this review, we discuss the roles of dormant ribosomes and their potential regulatory mechanisms. Furthermore, we highlight the paradigms that need to be answered in the field of ribosomal dormancy.
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Affiliation(s)
- Saloni Koli
- Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre, Navi Mumbai, India
| | - Sunil Shetty
- Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre, Navi Mumbai, India
- Homi Bhabha National Institute, Mumbai, India
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3
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Seely SM, Basu RS, Gagnon MG. Mechanistic insights into the alternative ribosome recycling by HflXr. Nucleic Acids Res 2024; 52:4053-4066. [PMID: 38407413 DOI: 10.1093/nar/gkae128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 02/02/2024] [Accepted: 02/19/2024] [Indexed: 02/27/2024] Open
Abstract
During stress conditions such as heat shock and antibiotic exposure, ribosomes stall on messenger RNAs, leading to inhibition of protein synthesis. To remobilize ribosomes, bacteria use rescue factors such as HflXr, a homolog of the conserved housekeeping GTPase HflX that catalyzes the dissociation of translationally inactive ribosomes into individual subunits. Here we use time-resolved cryo-electron microscopy to elucidate the mechanism of ribosome recycling by Listeria monocytogenes HflXr. Within the 70S ribosome, HflXr displaces helix H69 of the 50S subunit and induces long-range movements of the platform domain of the 30S subunit, disrupting inter-subunit bridges B2b, B2c, B4, B7a and B7b. Our findings unveil a unique ribosome recycling strategy by HflXr which is distinct from that mediated by RRF and EF-G. The resemblance between HflXr and housekeeping HflX suggests that the alternative ribosome recycling mechanism reported here is universal in the prokaryotic kingdom.
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Affiliation(s)
- Savannah M Seely
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Ritwika S Basu
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Matthieu G Gagnon
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA
- Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77555, USA
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4
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Bhattacharjee S, Feng X, Maji S, Dadhwal P, Zhang Z, Brown ZP, Frank J. Time resolution in cryo-EM using a PDMS-based microfluidic chip assembly and its application to the study of HflX-mediated ribosome recycling. Cell 2024; 187:782-796.e23. [PMID: 38244547 PMCID: PMC10872292 DOI: 10.1016/j.cell.2023.12.027] [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: 04/27/2023] [Revised: 10/13/2023] [Accepted: 12/19/2023] [Indexed: 01/22/2024]
Abstract
The rapid kinetics of biological processes and associated short-lived conformational changes pose a significant challenge in attempts to structurally visualize biomolecules during a reaction in real time. Conventionally, on-pathway intermediates have been trapped using chemical modifications or reduced temperature, giving limited insights. Here, we introduce a time-resolved cryo-EM method using a reusable PDMS-based microfluidic chip assembly with high reactant mixing efficiency. Coating of PDMS walls with SiO2 virtually eliminates non-specific sample adsorption and ensures maintenance of the stoichiometry of the reaction, rendering it highly reproducible. In an operating range from 10 to 1,000 ms, the device allows us to follow in vitro reactions of biological molecules at resolution levels in the range of 3 Å. By employing this method, we show the mechanism of progressive HflX-mediated splitting of the 70S E. coli ribosome in the presence of the GTP via capture of three high-resolution reaction intermediates within 140 ms.
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Affiliation(s)
- Sayan Bhattacharjee
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Xiangsong Feng
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA.
| | - Suvrajit Maji
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Prikshat Dadhwal
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Zhening Zhang
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Zuben P Brown
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA; Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
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5
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Mehrez M, Lecampion C, Ke H, Gorsane F, Field B. Insights into the function of the chloroplastic ribosome-associated GTPase high frequency of lysogenization X in Arabidopsis thaliana. PLANT DIRECT 2024; 8:e559. [PMID: 38222931 PMCID: PMC10784650 DOI: 10.1002/pld3.559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 06/15/2023] [Accepted: 12/07/2023] [Indexed: 01/16/2024]
Abstract
Ribosome-associated GTPases are conserved enzymes that participate in ribosome biogenesis and ribosome function. In bacteria, recent studies have identified HflX as a ribosome-associated GTPase that is involved in both ribosome biogenesis and recycling under stress conditions. Plants possess a chloroplastic HflX homolog, but its function remains unknown. Here, we characterized the role of HflX in the plant Arabidopsis thaliana. Our findings show that HflX does not affect normal plant growth, nor does it play an essential role in acclimation to several different stresses, including heat, manganese, cold, and salt stress under the conditions tested. However, we found that HflX is required for plant resistance to chloroplast translational stress mediated by the antibiotic lincomycin. Our results suggest that HflX is a chloroplast ribosome-associated protein that may play a role in the surveillance of translation. These findings provide new insight into the function of HflX as a ribosome-associated GTPase in plants and highlight the importance of investigating conserved proteins in different organisms to gain a comprehensive understanding of their biological roles.
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Affiliation(s)
- Marwa Mehrez
- Aix‐Marseille Univ, CEA, CNRS, BIAM, UMR7265MarseilleFrance
- Laboratory of Molecular Genetics, Immunology and Biotechnology, Faculty of Sciences of TunisUniversity of Tunis El ManarTunisTunisia
| | | | - Hang Ke
- Aix‐Marseille Univ, CEA, CNRS, BIAM, UMR7265MarseilleFrance
| | - Faten Gorsane
- Laboratory of Molecular Genetics, Immunology and Biotechnology, Faculty of Sciences of TunisUniversity of Tunis El ManarTunisTunisia
- Faculty of Sciences of BizerteUniversity of CarthageZarzounaTunisia
| | - Ben Field
- Aix‐Marseille Univ, CEA, CNRS, BIAM, UMR7265MarseilleFrance
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6
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Bhattacharjee S, Feng X, Maji S, Dadhwal P, Zhang Z, Brown ZP, Frank J. Time resolution in cryo-EM using a novel PDMS-based microfluidic chip assembly and its application to the study of HflX-mediated ribosome recycling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.25.525430. [PMID: 36747778 PMCID: PMC9900803 DOI: 10.1101/2023.01.25.525430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The rapid kinetics of biological processes and associated short-lived conformational changes pose a significant challenge in attempts to structurally visualize biomolecules during a reaction in real time. Conventionally, on-pathway intermediates have been trapped using chemical modifications or reduced temperature, giving limited insights. Here we introduce a novel time-resolved cryo-EM method using a reusable PDMS-based microfluidic chip assembly with high reactant mixing efficiency. Coating of PDMS walls with SiO2 virtually eliminates non-specific sample adsorption and ensures maintenance of the stoichiometry of the reaction, rendering it highly reproducible. In an operating range from 10 to 1000 ms, the device allows us to follow in vitro reactions of biological molecules at resolution levels in the range of 3 Å. By employing this method, we show for the first time the mechanism of progressive HlfX-mediated splitting of the 70S E. coli ribosome in the presence of the GTP, via capture of three high-resolution reaction intermediates within 140 ms.
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Affiliation(s)
- Sayan Bhattacharjee
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Xiangsong Feng
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Suvrajit Maji
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Prikshat Dadhwal
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Zhening Zhang
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
| | - Zuben P Brown
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
- Current address: Thermo Fisher Scientific, Oregon, USA
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10027, USA
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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7
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Safdari HA, Kasvandik S, Polte C, Ignatova Z, Tenson T, Wilson D. Structure of Escherichia coli heat shock protein Hsp15 in complex with the ribosomal 50S subunit bearing peptidyl-tRNA. Nucleic Acids Res 2022; 50:12515-12526. [PMID: 36370110 PMCID: PMC9757039 DOI: 10.1093/nar/gkac1035] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 10/13/2022] [Accepted: 11/09/2022] [Indexed: 11/14/2022] Open
Abstract
In Escherichia coli, the heat shock protein 15 (Hsp15) is part of the cellular response to elevated temperature. Hsp15 interacts with peptidyl-tRNA-50S complexes that arise upon dissociation of translating 70S ribosomes, and is proposed to facilitate their rescue and recycling. A previous structure of E. coli Hsp15 in complex with peptidyl-tRNA-50S complex reported a binding site located at the central protuberance of the 50S subunit. By contrast, recent structures of RqcP, the Hsp15 homolog in Bacillus subtilis, in complex with peptidyl-tRNA-50S complexes have revealed a distinct site positioned between the anticodon-stem-loop (ASL) of the P-site tRNA and H69 of the 23S rRNA. Here we demonstrate that exposure of E. coli cells to heat shock leads to a decrease in 70S ribosomes and accumulation of 50S subunits, thus identifying a natural substrate for Hsp15 binding. Additionally, we have determined a cryo-EM reconstruction of the Hsp15-50S-peptidyl-tRNA complex isolated from heat shocked E. coli cells, revealing that Hsp15 binds to the 50S-peptidyl-tRNA complex analogously to its B. subtilis homolog RqcP. Collectively, our findings support a model where Hsp15 stabilizes the peptidyl-tRNA in the P-site and thereby promotes access to the A-site for putative rescue factors to release the aberrant nascent polypeptide chain.
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Affiliation(s)
- Haaris A Safdari
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
| | - Sergo Kasvandik
- University of Tartu, Institute of Technology, 50411 Tartu, Estonia
| | - Christine Polte
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
| | - Zoya Ignatova
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
| | - Tanel Tenson
- University of Tartu, Institute of Technology, 50411 Tartu, Estonia
| | - Daniel N Wilson
- To whom correspondence should be addressed. Tel: +49 40 42838 2841;
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8
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Koller TO, Turnbull KJ, Vaitkevicius K, Crowe-McAuliffe C, Roghanian M, Bulvas O, Nakamoto JA, Kurata T, Julius C, Atkinson G, Johansson J, Hauryliuk V, Wilson D. Structural basis for HflXr-mediated antibiotic resistance in Listeria monocytogenes. Nucleic Acids Res 2022; 50:11285-11300. [PMID: 36300626 PMCID: PMC9638945 DOI: 10.1093/nar/gkac934] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 09/28/2022] [Accepted: 10/26/2022] [Indexed: 08/09/2023] Open
Abstract
HflX is a ubiquitous bacterial GTPase that splits and recycles stressed ribosomes. In addition to HflX, Listeria monocytogenes contains a second HflX homolog, HflXr. Unlike HflX, HflXr confers resistance to macrolide and lincosamide antibiotics by an experimentally unexplored mechanism. Here, we have determined cryo-EM structures of L. monocytogenes HflXr-50S and HflX-50S complexes as well as L. monocytogenes 70S ribosomes in the presence and absence of the lincosamide lincomycin. While the overall geometry of HflXr on the 50S subunit is similar to that of HflX, a loop within the N-terminal domain of HflXr, which is two amino acids longer than in HflX, reaches deeper into the peptidyltransferase center. Moreover, unlike HflX, the binding of HflXr induces conformational changes within adjacent rRNA nucleotides that would be incompatible with drug binding. These findings suggest that HflXr confers resistance using an allosteric ribosome protection mechanism, rather than by simply splitting and recycling antibiotic-stalled ribosomes.
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Affiliation(s)
| | | | - Karolis Vaitkevicius
- Department of Molecular Biology and Umeå Centre for Microbial Research (UCMR), Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
| | - Caillan Crowe-McAuliffe
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Mohammad Roghanian
- Department of Molecular Biology and Umeå Centre for Microbial Research (UCMR), Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
- Department of Clinical Microbiology, Rigshospitalet, 2200 Copenhagen, Denmark
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Ondřej Bulvas
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
- Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic
| | - Jose A Nakamoto
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Tatsuaki Kurata
- Department of Molecular Biology and Umeå Centre for Microbial Research (UCMR), Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Christina Julius
- Department of Molecular Biology and Umeå Centre for Microbial Research (UCMR), Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
| | - Gemma C Atkinson
- Department of Experimental Medical Science, Lund University, 221 00 Lund, Sweden
| | - Jörgen Johansson
- Department of Molecular Biology and Umeå Centre for Microbial Research (UCMR), Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, 90187 Umeå, Sweden
| | | | - Daniel N Wilson
- To whom correspondence should be addressed. Tel: +49 40 42838 2841;
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9
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Kumar R, Roy C, Datta S. Delineating specific regions of N- terminal domain of T3SS ATPase YsaN of Yersinia enterocolitica governing its different oligomerization states. Front Mol Biosci 2022; 9:967974. [PMID: 36158578 PMCID: PMC9493007 DOI: 10.3389/fmolb.2022.967974] [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: 06/13/2022] [Accepted: 08/16/2022] [Indexed: 11/13/2022] Open
Abstract
Oligomerization of YsaN, a putative T3SS-ATPase is a necessary and crucial event for T3SS functioning in Y. enterocolitica. Different oligomeric states have been proposed for similar ATPases, yet, the true nature of its activation and formation of different oligomers is still poorly understood. In-vitro studies of YsaN reveal that its activation and oligomerization depend on its N-terminal region and occur as a result of active catalysis of ATP in an ATP concentration-dependent manner following two-step cooperative kinetics. Also, the N-terminal 83 amino acid residues of YsaN are crucial for higher-order oligomer formation while YsaN∆83 is capable of hexamer formation upon oligomerization. Enzyme kinetics study shows reduced ATPase activity of YsaN∆83 (3.19 ± 0.09 μmol/min/mg) in comparison to YsaN (9.076 ± 0.72 μmol/min/mg). Negative-TEM study of YsaN and YsaN∆83 oligomer suggests that the formation of higher-order oligomer (probably dodecamer) occurs by stacking of two hexamers through their N-terminal faces involving N-terminal 83 amino acid residues which have been further supported by the docking of two hexamers during the in-silico study. These results suggest that YsaN is an oligomerization-activated T3SS ATPase, where distinct regions of its N-terminal domain regulate its different oligomeric nature and is essential for its activation.
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10
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How to save a bacterial ribosome in times of stress. Semin Cell Dev Biol 2022; 136:3-12. [PMID: 35331628 DOI: 10.1016/j.semcdb.2022.03.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 03/01/2022] [Accepted: 03/11/2022] [Indexed: 11/21/2022]
Abstract
Biogenesis of ribosomes is one of the most cost- and resource-intensive processes in all living cells. In bacteria, ribosome biogenesis is rate-limiting for growth and must be tightly coordinated to yield maximum fitness of the cells. Since bacteria are continuously facing environmental changes and stress conditions, they have developed sophisticated systems to sense and regulate their nutritional status. Amino acid starvation leads to the synthesis and accumulation of the nucleotide-based second messengers ppGpp and pppGpp [(p)ppGpp], which in turn function as central players of a pleiotropic metabolic adaptation mechanism named the stringent response. Here, we review our current knowledge on the multiple roles of (p)ppGpp in the stress-related modulation of the prokaryotic protein biosynthesis machinery with the ribosome as its core constituent. The alarmones ppGpp/pppGpp act as competitors of their GDP/GTP counterparts, to affect a multitude of ribosome-associated P-loop GTPases involved in the translation cycle, ribosome biogenesis and hibernation. A similar mode of inhibition has been found for the GTPases of the proteins involved in the SRP-dependent membrane-targeting machinery present in the periphery of the ribosome. In this sense, during stringent conditions, binding of (p)ppGpp restricts the membrane insertion and secretion of proteins. Altogether, we highlight the enormously resource-intensive stages of ribosome biogenesis as a critical regulatory hub of the stringent response that ultimately tunes the protein synthesis capacity and consequently the survival of the cell.
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11
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Nadler F, Lavdovskaia E, Richter-Dennerlein R. Maintaining mitochondrial ribosome function: The role of ribosome rescue and recycling factors. RNA Biol 2021; 19:117-131. [PMID: 34923906 PMCID: PMC8786322 DOI: 10.1080/15476286.2021.2015561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
The universally conserved process of protein biosynthesis is crucial for maintaining cellular homoeostasis and in eukaryotes, mitochondrial translation is essential for aerobic energy production. Mitochondrial ribosomes (mitoribosomes) are highly specialized to synthesize 13 core subunits of the oxidative phosphorylation (OXPHOS) complexes. Although the mitochondrial translation machinery traces its origin from a bacterial ancestor, it has acquired substantial differences within this endosymbiotic environment. The cycle of mitoribosome function proceeds through the conserved canonical steps of initiation, elongation, termination and mitoribosome recycling. However, when mitoribosomes operate in the context of limited translation factors or on aberrant mRNAs, they can become stalled and activation of rescue mechanisms is required. This review summarizes recent advances in the understanding of protein biosynthesis in mitochondria, focusing especially on the mechanistic and physiological details of translation termination, and mitoribosome recycling and rescue.
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Affiliation(s)
- Franziska Nadler
- Department of Cellular Biochemistry, University Medical Center Goettingen, Goettingen, Germany
| | - Elena Lavdovskaia
- Department of Cellular Biochemistry, University Medical Center Goettingen, Goettingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Goettingen, Goettingen, Germany
| | - Ricarda Richter-Dennerlein
- Department of Cellular Biochemistry, University Medical Center Goettingen, Goettingen, Germany.,Cluster of Excellence "Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells" (MBExC), University of Goettingen, Goettingen, Germany
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12
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The Stringent Response Inhibits 70S Ribosome Formation in Staphylococcus aureus by Impeding GTPase-Ribosome Interactions. mBio 2021; 12:e0267921. [PMID: 34749534 PMCID: PMC8579695 DOI: 10.1128/mbio.02679-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
During nutrient limitation, bacteria produce the alarmones (p)ppGpp as effectors of a stress signaling network termed the stringent response. RsgA, RbgA, Era, and HflX are four ribosome-associated GTPases (RA-GTPases) that bind to (p)ppGpp in Staphylococcus aureus. These enzymes are cofactors in ribosome assembly, where they cycle between the ON (GTP-bound) and OFF (GDP-bound) ribosome-associated states. Entry into the OFF state occurs upon hydrolysis of GTP, with GTPase activity increasing substantially upon ribosome association. When bound to (p)ppGpp, GTPase activity is inhibited, reducing 70S ribosome assembly and growth. Here, we determine how (p)ppGpp impacts RA-GTPase-ribosome interactions. We show that RA-GTPases preferentially bind to 5′-diphosphate-containing nucleotides GDP and ppGpp over GTP, which is likely exploited as a regulatory mechanism within the cell to shut down ribosome biogenesis during stress. Stopped-flow fluorescence and association assays reveal that when bound to (p)ppGpp, the association of RA-GTPases to ribosomal subunits is destabilized, both in vitro and within bacterial cells. Consistently, structural analysis of the ppGpp-bound RA-GTPase RsgA reveals an OFF-state conformation similar to the GDP-bound state, with the G2/switch I loop adopting a conformation incompatible with ribosome association. Altogether, we highlight (p)ppGpp-mediated inhibition of RA-GTPases as a major mechanism of stringent response-mediated ribosome assembly and growth control.
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13
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HflX is a GTPase that controls hypoxia-induced replication arrest in slow-growing mycobacteria. Proc Natl Acad Sci U S A 2021; 118:2006717118. [PMID: 33723035 DOI: 10.1073/pnas.2006717118] [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: 11/18/2022] Open
Abstract
GTPase high frequency of lysogenization X (HflX) is highly conserved in prokaryotes and acts as a ribosome-splitting factor as part of the heat shock response in Escherichia coli. Here we report that HflX produced by slow-growing Mycobacterium bovis bacillus Calmette-Guérin (BCG) is a GTPase that plays a critical role in the pathogen's transition to a nonreplicating, drug-tolerant state in response to hypoxia. Indeed, HflX-deficient M. bovis BCG (KO) replicated markedly faster in the microaerophilic phase of a hypoxia model that resulted in premature entry into dormancy. The KO mutant displayed hallmarks of nonreplicating mycobacteria, including phenotypic drug resistance, altered morphology, low intracellular ATP levels, and overexpression of Dormancy (Dos) regulon proteins. Mice nasally infected with HflX KO mutant displayed increased bacterial burden in the lungs, spleen, and lymph nodes during the chronic phase of infection, consistent with the higher replication rate observed in vitro in microaerophilic conditions. Unlike fast growing mycobacteria, M. bovis BCG HlfX was not involved in antibiotic resistance under aerobic growth. Proteomics, pull-down, and ribo-sequencing approaches supported that mycobacterial HflX is a ribosome-binding protein that controls translational activity of the cell. With HflX fully conserved between M. bovis BCG and M. tuberculosis, our work provides further insights into the molecular mechanisms deployed by pathogenic mycobacteria to adapt to their hypoxic microenvironment.
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14
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Kumar N, Sharma S, Kaushal PS. Protein synthesis in Mycobacterium tuberculosis as a potential target for therapeutic interventions. Mol Aspects Med 2021; 81:101002. [PMID: 34344520 DOI: 10.1016/j.mam.2021.101002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 07/11/2021] [Accepted: 07/16/2021] [Indexed: 12/18/2022]
Abstract
Mycobacterium tuberculosis (Mtb) causes one of humankind's deadliest diseases, tuberculosis. Mtb protein synthesis machinery possesses several unique species-specific features, including its ribosome that carries two mycobacterial specific ribosomal proteins, bL37 and bS22, and ribosomal RNA segments. Since the protein synthesis is a vital cellular process that occurs on the ribosome, a detailed knowledge of the structure and function of mycobacterial ribosomes is essential to understand the cell's proteome by translation regulation. Like in many bacterial species such as Bacillus subtilis and Streptomyces coelicolor, two distinct populations of ribosomes have been identified in Mtb. Under low-zinc conditions, Mtb ribosomal proteins S14, S18, L28, and L33 are replaced with their non-zinc binding paralogues. Depending upon the nature of physiological stress, species-specific modulation of translation by stress factors and toxins that interact with the ribosome have been reported. In addition, about one-fourth of messenger RNAs in mycobacteria have been reported to be leaderless, i.e., without 5' UTR regions. However, the mechanism by which they are recruited to the Mtb ribosome is not understood. In this review, we highlight the mycobacteria-specific features of the translation apparatus and propose exploiting these features to improve the efficacy and specificity of existing antibiotics used to treat tuberculosis.
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Affiliation(s)
- Niraj Kumar
- Structural Biology & Translation Regulation Laboratory, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, 121 001, India
| | - Shivani Sharma
- Structural Biology & Translation Regulation Laboratory, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, 121 001, India
| | - Prem S Kaushal
- Structural Biology & Translation Regulation Laboratory, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, 121 001, India.
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15
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Brewer KI, Greenlee EB, Higgs G, Yu D, Mirihana Arachchilage G, Chen X, King N, White N, Breaker RR. Comprehensive discovery of novel structured noncoding RNAs in 26 bacterial genomes. RNA Biol 2021; 18:2417-2432. [PMID: 33970790 PMCID: PMC8632094 DOI: 10.1080/15476286.2021.1917891] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/30/2022] Open
Abstract
Comparative sequence analysis methods are highly effective for uncovering novel classes of structured noncoding RNAs (ncRNAs) from bacterial genomic DNA sequence datasets. Previously, we developed a computational pipeline to more comprehensively identify structured ncRNA representatives from individual bacterial genomes. This search process exploits the fact that genomic regions serving as templates for the transcription of structured RNAs tend to be present in longer than average noncoding 'intergenic regions' (IGRs) that are enriched in G and C nucleotides compared to the remainder of the genome. In the present study, we apply this computational pipeline to identify structured ncRNA candidates from 26 diverse bacterial species. Numerous novel structured ncRNA motifs were discovered, including several riboswitch candidates, one whose ligand has been identified and others that have yet to be experimentally validated. Our findings support recent predictions that hundreds of novel ribo-switch classes and other ncRNAs remain undiscovered among the limited number of bacterial species whose genomes have been completely sequenced.
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Affiliation(s)
- Kenneth I Brewer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Etienne B Greenlee
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Gadareth Higgs
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Diane Yu
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | | | - Xi Chen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Nicholas King
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA
| | - Neil White
- Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
| | - Ronald R Breaker
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.,Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, USA
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16
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Lavdovskaia E, Denks K, Nadler F, Steube E, Linden A, Urlaub H, Rodnina MV, Richter-Dennerlein R. Dual function of GTPBP6 in biogenesis and recycling of human mitochondrial ribosomes. Nucleic Acids Res 2021; 48:12929-12942. [PMID: 33264405 PMCID: PMC7736812 DOI: 10.1093/nar/gkaa1132] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/19/2020] [Accepted: 11/09/2020] [Indexed: 01/01/2023] Open
Abstract
Translation and ribosome biogenesis in mitochondria require auxiliary factors that ensure rapid and accurate synthesis of mitochondrial proteins. Defects in translation are associated with oxidative phosphorylation deficiency and cause severe human diseases, but the exact roles of mitochondrial translation-associated factors are not known. Here we identify the functions of GTPBP6, a homolog of the bacterial ribosome-recycling factor HflX, in human mitochondria. Similarly to HflX, GTPBP6 facilitates the dissociation of ribosomes in vitro and in vivo. In contrast to HflX, GTPBP6 is also required for the assembly of mitochondrial ribosomes. GTPBP6 ablation leads to accumulation of late assembly intermediate(s) of the large ribosomal subunit containing ribosome biogenesis factors MTERF4, NSUN4, MALSU1 and the GTPases GTPBP5, GTPBP7 and GTPBP10. Our data show that GTPBP6 has a dual function acting in ribosome recycling and biogenesis. These findings contribute to our understanding of large ribosomal subunit assembly as well as ribosome recycling pathway in mitochondria.
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Affiliation(s)
- Elena Lavdovskaia
- Department of Cellular Biochemistry, University Medical Center Goettingen, D-37073 Goettingen, Germany.,Cluster of Excellence 'Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells' (MBExC), University of Goettingen, Goettingen, Germany
| | - Kärt Denks
- Cluster of Excellence 'Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells' (MBExC), University of Goettingen, Goettingen, Germany.,Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Goettingen, Germany
| | - Franziska Nadler
- Department of Cellular Biochemistry, University Medical Center Goettingen, D-37073 Goettingen, Germany
| | - Emely Steube
- Department of Cellular Biochemistry, University Medical Center Goettingen, D-37073 Goettingen, Germany
| | - Andreas Linden
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, D-37077 Goettingen, Germany.,Bioanalytics, Institute for Clinical Chemistry, University Medical Center Goettingen, D-37073 Goettingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, D-37077 Goettingen, Germany.,Bioanalytics, Institute for Clinical Chemistry, University Medical Center Goettingen, D-37073 Goettingen, Germany
| | - Marina V Rodnina
- Cluster of Excellence 'Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells' (MBExC), University of Goettingen, Goettingen, Germany.,Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Goettingen, Germany
| | - Ricarda Richter-Dennerlein
- Department of Cellular Biochemistry, University Medical Center Goettingen, D-37073 Goettingen, Germany.,Cluster of Excellence 'Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells' (MBExC), University of Goettingen, Goettingen, Germany
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17
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Role of GTPases in Driving Mitoribosome Assembly. Trends Cell Biol 2021; 31:284-297. [PMID: 33419649 DOI: 10.1016/j.tcb.2020.12.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 12/01/2020] [Accepted: 12/11/2020] [Indexed: 01/08/2023]
Abstract
Mitoribosomes catalyze essential protein synthesis within mitochondria. Mitoribosome biogenesis is assisted by an increasing number of assembly factors, among which guanosine triphosphate hydrolases (GTPases) are the most abundant class. Here, we review recent progress in our understanding of mitoribosome assembly GTPases. We describe their shared and specific features and mechanisms of action, compare them with their bacterial counterparts, and discuss their possible roles in the assembly of small or large mitoribosomal subunits and the formation of the monosome by establishing quality-control checkpoints during these processes. Furthermore, following the recent unification of the nomenclature for the mitoribosomal proteins, we also propose a unified nomenclature for mitoribosome assembly GTPases.
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18
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Ferdosh S, Banerjee S, Pathak BK, Sengupta J, Barat C. Hibernating ribosomes exhibit chaperoning activity but can resist unfolded protein-mediated subunit dissociation. FEBS J 2020; 288:1305-1324. [PMID: 32649051 DOI: 10.1111/febs.15479] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 06/24/2020] [Accepted: 07/07/2020] [Indexed: 02/03/2023]
Abstract
Ribosome hibernation is a prominent cellular strategy to modulate protein synthesis during starvation and the stationary phase of bacterial cell growth. Translational suppression involves the formation of either factor-bound inactive 70S monomers or dimeric 100S hibernating ribosomal complexes, the biological significance of which is poorly understood. Here, we demonstrate that the Escherichia coli 70S ribosome associated with stationary phase factors hibernation promoting factor or protein Y or ribosome-associated inhibitor A and the 100S ribosome isolated from both Gram-negative and Gram-positive bacteria are resistant to unfolded protein-mediated subunit dissociation and subsequent degradation by cellular ribonucleases. Considering that the increase in cellular stress is accompanied by accumulation of unfolded proteins, such resistance of hibernating ribosomes towards dissociation might contribute to their maintenance during the stationary phase. Analysis of existing structures provided clues on the mechanism of inhibition of the unfolded protein-mediated disassembly in case of hibernating factor-bound ribosome. Further, the factor-bound 70S and 100S ribosomes can suppress protein aggregation and assist in protein folding. The chaperoning activity of these ribosomes is the first evidence of a potential biological activity of the hibernating ribosome that might be crucial for cell survival under stress conditions.
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Affiliation(s)
- Sehnaz Ferdosh
- Department of Biotechnology, St. Xavier's College, Kolkata, India
| | - Senjuti Banerjee
- Department of Biotechnology, St. Xavier's College, Kolkata, India
| | - Bani K Pathak
- Structural Biology and Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific and Industrial Research), Kolkata, India
| | - Jayati Sengupta
- Structural Biology and Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific and Industrial Research), Kolkata, India
| | - Chandana Barat
- Department of Biotechnology, St. Xavier's College, Kolkata, India
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19
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Basu A, Shields KE, Yap MNF. The hibernating 100S complex is a target of ribosome-recycling factor and elongation factor G in Staphylococcus aureus. J Biol Chem 2020; 295:6053-6063. [PMID: 32209660 PMCID: PMC7196661 DOI: 10.1074/jbc.ra119.012307] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 03/18/2020] [Indexed: 12/24/2022] Open
Abstract
The formation of translationally inactive 70S dimers (called 100S ribosomes) by hibernation-promoting factor is a widespread survival strategy among bacteria. Ribosome dimerization is thought to be reversible, with the dissociation of the 100S complexes enabling ribosome recycling for participation in new rounds of translation. The precise pathway of 100S ribosome recycling has been unclear. We previously found that the heat-shock GTPase HflX in the human pathogen Staphylococcus aureus is a minor disassembly factor. Cells lacking hflX do not accumulate 100S ribosomes unless they are subjected to heat exposure, suggesting the existence of an alternative pathway during nonstressed conditions. Here, we provide biochemical and genetic evidence that two essential translation factors, ribosome-recycling factor (RRF) and GTPase elongation factor G (EF-G), synergistically split 100S ribosomes in a GTP-dependent but tRNA translocation-independent manner. We found that although HflX and the RRF/EF-G pair are functionally interchangeable, HflX is expressed at low levels and is dispensable under normal growth conditions. The bacterial RRF/EF-G pair was previously known to target only the post-termination 70S complexes; our results reveal a new role in the reversal of ribosome hibernation that is intimately linked to bacterial pathogenesis, persister formation, stress responses, and ribosome integrity.
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Affiliation(s)
- Arnab Basu
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104
| | - Kathryn E Shields
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104
| | - Mee-Ngan F Yap
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri 63104; Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611.
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20
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Li C, Murugaiyan J, Thomas C, Alter T, Riedel C. Isolate Specific Cold Response of Yersinia enterocolitica in Transcriptional, Proteomic, and Membrane Physiological Changes. Front Microbiol 2020; 10:3037. [PMID: 32038527 PMCID: PMC6990146 DOI: 10.3389/fmicb.2019.03037] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2019] [Accepted: 12/17/2019] [Indexed: 12/24/2022] Open
Abstract
Yersinia enterocolitica, a zoonotic foodborne pathogen, is able to withstand low temperatures. This psychrotrophic ability allows it to multiply in food stored in refrigerators. However, little is known about the Y. enterocolitica cold response. In this study, isolate-specific behavior at 4°C was demonstrated and the cold response was investigated by examining changes in phenotype, gene expression, and the proteome. Altered expression of cold-responsive genes showed that the ability to survive at low temperature depends on the capacity to acclimate and adapt to cold stress. This cold acclimation at the transcriptional level involves the transient induction and effective repression of cold-shock protein (Csp) genes. Moreover, the resumption of expression of genes encoding other non-Csp is essential during prolonged adaptation. Based on proteomic analyses, the predominant functional categories of cold-responsive proteins are associated with protein synthesis, cell membrane structure, and cell motility. In addition, changes in membrane fluidity and motility were shown to be important in the cold response of Y. enterocolitica. Isolate-specific differences in the transcription of membrane fluidity- and motility-related genes provided evidence to classify strains within a spectrum of cold response. The combination of different approaches has permitted the systematic description of the Y. enterocolitica cold response and gives a better understanding of the physiological processes underlying this phenomenon.
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Affiliation(s)
- Chenyang Li
- Institute of Food Safety and Food Hygiene, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Jayaseelan Murugaiyan
- Institute for Animal Hygiene and Environmental Health, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
- Department of Biotechnology, SRM University AP, Amaravati, India
| | - Christian Thomas
- Department of Food Science and Technology, Beuth University of Applied Sciences Berlin, Berlin, Germany
| | - Thomas Alter
- Institute of Food Safety and Food Hygiene, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Carolin Riedel
- Institute of Food Safety and Food Hygiene, Department of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
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21
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Bennison DJ, Irving SE, Corrigan RM. The Impact of the Stringent Response on TRAFAC GTPases and Prokaryotic Ribosome Assembly. Cells 2019; 8:cells8111313. [PMID: 31653044 PMCID: PMC6912228 DOI: 10.3390/cells8111313] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/17/2019] [Accepted: 10/23/2019] [Indexed: 12/24/2022] Open
Abstract
Many facets of ribosome biogenesis and function, including ribosomal RNA (rRNA) transcription, 70S assembly and protein translation, are negatively impacted upon induction of a nutrient stress-sensing signalling pathway termed the stringent response. This stress response is mediated by the alarmones guanosine tetra- and penta-phosphate ((p)ppGpp), the accumulation of which leads to a massive cellular response that slows growth and aids survival. The 70S bacterial ribosome is an intricate structure, with assembly both complex and highly modular. Presiding over the assembly process is a group of P-loop GTPases within the TRAFAC (Translation Factor Association) superclass that are crucial for correct positioning of both early and late stage ribosomal proteins (r-proteins) onto the rRNA. Often described as 'molecular switches', members of this GTPase superfamily readily bind and hydrolyse GTP to GDP in a cyclic manner that alters the propensity of the GTPase to carry out a function. TRAFAC GTPases are considered to act as checkpoints to ribosome assembly, involved in binding to immature sections in the GTP-bound state, preventing further r-protein association until maturation is complete. Here we review our current understanding of the impact of the stringent response and (p)ppGpp production on ribosome maturation in prokaryotic cells, focusing on the inhibition of (p)ppGpp on GTPase-mediated subunit assembly, but also touching upon the inhibition of rRNA transcription and protein translation.
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Affiliation(s)
- Daniel J Bennison
- The Florey Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
| | - Sophie E Irving
- The Florey Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
| | - Rebecca M Corrigan
- The Florey Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
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22
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Abstract
Antibiotics have been widely used to treat bacterial infections and are also found in the environment. Bacteria have evolved various resistance mechanisms, allowing them to overcome antibiotic exposure and raising important health issues. Here, we report a bacterial antibiotic resistance mechanism, based on ribosome splitting and recycling, ensuring efficient translation even in presence of lincomycin and erythromycin, two antibiotics that block protein synthesis. This mechanism is mediated by a HflX-like protein, encoded by lmo0762 in Listeria monocytogenes, whose expression is tightly regulated by a transcriptional attenuation mechanism. This gene increases bacterial fitness in the environment. Our results raise the possibility that other antibiotic-induced resistance mechanisms remain to be discovered. To overcome the action of antibiotics, bacteria have evolved a variety of different strategies, such as drug modification, target mutation, and efflux pumps. Recently, we performed a genome-wide analysis of Listeria monocytogenes gene expression after growth in the presence of antibiotics, identifying genes that are up-regulated upon antibiotic treatment. One of them, lmo0762, is a homolog of hflX, which encodes a heat shock protein that rescues stalled ribosomes by separating their two subunits. To our knowledge, ribosome splitting has never been described as an antibiotic resistance mechanism. We thus investigated the role of lmo0762 in antibiotic resistance. First, we demonstrated that lmo0762 is an antibiotic resistance gene that confers protection against lincomycin and erythromycin, and that we renamed hflXr (hflX resistance). We show that hflXr expression is regulated by a transcription attenuation mechanism relying on the presence of alternative RNA structures and a small ORF encoding a 14 amino acid peptide containing the RLR motif, characteristic of macrolide resistance genes. We also provide evidence that HflXr is involved in ribosome recycling in presence of antibiotics. Interestingly, L. monocytogenes possesses another copy of hflX, lmo1296, that is not involved in antibiotic resistance. Phylogenetic analysis shows several events of hflXr duplication in prokaryotes and widespread presence of hflXr in Firmicutes. Overall, this study reveals the Listeria hflXr as the founding member of a family of antibiotic resistance genes. The resistance conferred by this gene is probably of importance in the environment and within microbial communities.
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23
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Structural modules of the stress-induced protein HflX: an outlook on its evolution and biological role. Curr Genet 2018; 65:363-370. [PMID: 30448945 DOI: 10.1007/s00294-018-0905-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 12/23/2022]
Abstract
Multifunctional proteins often show modular structures. A functional domain and the structural modules within the domain show evolutionary conservation of their spatial arrangement since that gives the protein its functionality. However, the question remains as to how members of different domains of life (Archaea, Bacteria, Eukarya), polish and perfect these modules within conserved multidomain proteins, to tailor functional proteins according to their specific requirements. In the quest for plausible answers to this question, we studied the bacterial protein HflX. HflX is a universally conserved member of the Obg-GTPase superfamily but its functional role in Archaea and Eukarya is barely known. It is a multidomain protein and possesses, in addition to its conserved GTPase domain, an ATP-binding N-terminal domain. It is involved in heat stress response in Escherichia coli and our laboratory recently identified an ATP-dependent RNA helicase activity of E. coli HflX, which is likely instrumental in rescuing ribosomes during heat stress. Because perception and response to stress is expected to be different in different life forms, the question is whether this activity is preserved in higher organisms or not. Thus, we explored the evolution pattern of different structural modules of HflX, with particular emphasis on the ATP-binding domain, to understand plausible biological role of HflX in other forms of life. Our analyses indicate that, while the evolutionary pattern of the GTPase domain follows a conserved phylogeny, conservation of the ATP-binding domain shows a complicated pattern. The limited analysis described here hints towards possible evolutionary adaptations and modifications of the domain, something which needs to be investigated in more depth in homologs from other life forms. Deciphering how nature 'tweaks' such modules, both structurally and functionally, may help in understanding the evolution of such proteins, and, on a large-scale, of stress-related proteins in general as well.
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