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Yuce M, Ates B, Yasar NI, Sungur FA, Kurkcuoglu O. A computational workflow to determine drug candidates alternative to aminoglycosides targeting the decoding center of E. coli ribosome. J Mol Graph Model 2024; 131:108817. [PMID: 38976944 DOI: 10.1016/j.jmgm.2024.108817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/08/2024] [Accepted: 07/03/2024] [Indexed: 07/10/2024]
Abstract
The global antibiotic resistance problem necessitates fast and effective approaches to finding novel inhibitors to treat bacterial infections. In this study, we propose a computational workflow to identify plausible high-affinity compounds from FDA-approved, investigational, and experimental libraries for the decoding center on the small subunit 30S of the E. coli ribosome. The workflow basically consists of two molecular docking calculations on the intact 30S, followed by molecular dynamics (MD) simulations coupled with MM-GBSA calculations on a truncated ribosome structure. The parameters used in the molecular docking suits, Glide and AutoDock Vina, as well as in the MD simulations with Desmond were carefully adjusted to obtain expected interactions for the ligand-rRNA complexes. A filtering procedure was followed, considering a fingerprint based on aminoglycoside's binding site on the 30S to obtain seven hit compounds either with different clinical usages or aminoglycoside derivatives under investigation, suggested for in vitro studies. The detailed workflow developed in this study promises an effective and fast approach for the estimation of binding free energies of large protein-RNA and ligand complexes.
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Affiliation(s)
- Merve Yuce
- Istanbul Technical University, Department of Chemical Engineering, Istanbul, 34469, Turkey.
| | - Beril Ates
- Istanbul Technical University, Department of Chemical Engineering, Istanbul, 34469, Turkey.
| | - Nesrin Isil Yasar
- Istanbul Technical University, Computational Science and Engineering Division, Informatics Institute, Istanbul, 34469, Turkey.
| | - Fethiye Aylin Sungur
- Istanbul Technical University, Computational Science and Engineering Division, Informatics Institute, Istanbul, 34469, Turkey.
| | - Ozge Kurkcuoglu
- Istanbul Technical University, Department of Chemical Engineering, Istanbul, 34469, Turkey.
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2
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Ali Z, Kaur S, Kukhta T, Abu-Saleh AAAA, Jhunjhunwala A, Mitra A, Trant JF, Sharma P. Structural Mapping of the Base Stacks Containing Post-transcriptionally Modified Bases in RNA. J Phys Chem B 2023. [PMID: 37369074 DOI: 10.1021/acs.jpcb.3c02268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
Post-transcriptionally modified bases play vital roles in many biochemical processes involving RNA. Analysis of the non-covalent interactions associated with these bases in RNA is crucial for providing a more complete understanding of the RNA structure and function; however, the characterization of these interactions remains understudied. To address this limitation, we present a comprehensive analysis of base stacks involving all crystallographic occurrences of the most biologically relevant modified bases in a large dataset of high-resolution RNA crystal structures. This is accompanied by a geometrical classification of the stacking contacts using our established tools. Coupled with quantum chemical calculations and an analysis of the specific structural context of these stacks, this provides a map of the stacking conformations available to modified bases in RNA. Overall, our analysis is expected to facilitate structural research on altered RNA bases.
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Affiliation(s)
- Zakir Ali
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India
| | - Sarabjeet Kaur
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India
- Surface Chemistry and Catalysis: Characterisation and Application Team (COK-KAT), Leuven (Arenberg) Celestijnenlaan 200f─Box 2461, 3001 Leuven, Belgium
| | - Teagan Kukhta
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
| | - Abd Al-Aziz A Abu-Saleh
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
- Binary Star Research Services, LaSalle, Ontario N9J 3X8, Canada
| | - Ayush Jhunjhunwala
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology (IIIT-H), Gachibowli, Hyderabad, Telangana 500032, India
| | - Abhijit Mitra
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology (IIIT-H), Gachibowli, Hyderabad, Telangana 500032, India
| | - John F Trant
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
- Binary Star Research Services, LaSalle, Ontario N9J 3X8, Canada
| | - Purshotam Sharma
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India
- Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
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3
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Lee C, Ye Q, Shin E, Ting T, Lee SJ. Acquisition of Streptomycin Resistance by Oxidative Stress Induced by Hydrogen Peroxide in Radiation-Resistant Bacterium Deinococcus geothermalis. Int J Mol Sci 2022; 23:ijms23179764. [PMID: 36077162 PMCID: PMC9456066 DOI: 10.3390/ijms23179764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/09/2022] [Accepted: 08/24/2022] [Indexed: 12/01/2022] Open
Abstract
Streptomycin is used primarily to treat bacterial infections, including brucellosis, plague, and tuberculosis. Streptomycin resistance easily develops in numerous bacteria through the inhibition of antibiotic transfer, the production of aminoglycoside-modifying enzymes, or mutations in ribosomal components with clinical doses of streptomycin treatment. (1) Background: A transposable insertion sequence is one of the mutation agents in bacterial genomes under oxidative stress. (2) Methods: In the radiation-resistant bacterium Deinococcus geothermalis subjected to chronic oxidative stress induced by 20 mM hydrogen peroxide, active transposition of an insertion sequence element and several point mutations in three streptomycin resistance (SmR)-related genes (rsmG, rpsL, and mthA) were identified. (3) Results: ISDge6 of the IS5 family integrated into the rsmG gene (dgeo_2335), called SrsmG, encodes a ribosomal guanosine methyltransferase resulting in streptomycin resistance. In the case of dgeo_2840-disrupted mutant strains (S1 and S2), growth inhibition under antibiotic-free conditions was recovered with increased growth yields in the presence of 50 µg/mL streptomycin due to a streptomycin-dependent (SmD) mutation. These mutants have a predicted proline-to-leucine substitution at the 91st residue of ribosomal protein S12 in the decoding center. (4) Conclusions: Our findings show that the active transposition of a unique IS element under oxidative stress conditions conferred antibiotic resistance through the disruption of rsmG. Furthermore, chronic oxidative stress induced by hydrogen peroxide also induced streptomycin resistance caused by point and frameshift mutations of streptomycin-interacting residues such as K43, K88, and P91 in RpsL and four genes for streptomycin resistance.
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4
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Osterman IA, Dontsova OA, Sergiev PV. rRNA Methylation and Antibiotic Resistance. BIOCHEMISTRY (MOSCOW) 2021; 85:1335-1349. [PMID: 33280577 DOI: 10.1134/s000629792011005x] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Methylation of nucleotides in rRNA is one of the basic mechanisms of bacterial resistance to protein synthesis inhibitors. The genes for corresponding methyltransferases have been found in producer strains and clinical isolates of pathogenic bacteria. In some cases, rRNA methylation by housekeeping enzymes is, on the contrary, required for the action of antibiotics. The effects of rRNA modifications associated with antibiotic efficacy may be cooperative or mutually exclusive. Evolutionary relationships between the systems of rRNA modification by housekeeping enzymes and antibiotic resistance-related methyltransferases are of particular interest. In this review, we discuss the above topics in detail.
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Affiliation(s)
- I A Osterman
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Skolkovo, 143028, Russia.,Faculty of Chemistry, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - O A Dontsova
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Skolkovo, 143028, Russia.,Faculty of Chemistry, Lomonosov Moscow State University, Moscow, 119991, Russia.,Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | - P V Sergiev
- Center of Life Sciences, Skolkovo Institute of Science and Technology, Skolkovo, 143028, Russia. .,Faculty of Chemistry, Lomonosov Moscow State University, Moscow, 119991, Russia.,Institute of Functional Genomics, Lomonosov Moscow State University, Moscow, 119991, Russia
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5
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Abedeera SM, Hawkins CM, Abeysirigunawardena SC. RsmG forms stable complexes with premature small subunit rRNA during bacterial ribosome biogenesis. RSC Adv 2020; 10:22361-22369. [PMID: 35514586 PMCID: PMC9054591 DOI: 10.1039/d0ra02732d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 06/01/2020] [Indexed: 12/22/2022] Open
Abstract
The ribosome is the ribonucleoprotein machine that carries out protein biosynthesis in all forms of life. Perfect synchronization between ribosomal RNA (rRNA) transcription, folding, post-transcriptional modification, maturation, and assembly of r-proteins is essential for the rapid formation of structurally and functionally accurate ribosomes. Many RNA nucleotide modification enzymes may function as assembly factors that oversee the accuracy of ribosome assembly. The protein RsmG is a methyltransferase enzyme that is responsible for N7 methylation in G527 of 16S rRNA. Here we illustrate the ability of RsmG to bind various premature small subunit ribosomal RNAs with contrasting affinities. Protein RsmG binds with approximately 15-times higher affinity to premature 16S rRNA with the full leader sequence compared to that of mature 16S rRNA. Various r-proteins which bind to the 5′-domain influence RsmG binding. The observed binding cooperativity between RsmG and r-proteins is sensitive to the maturation status of premature small subunit rRNA. However, neither the maturation of 16S rRNA nor the presence of various r-proteins significantly influence the methylation activity of RsmG. The capability of RsmG to bind to premature small subunit rRNA and alter its binding preference to various RNA–protein complexes based on the maturation of rRNA indicates its ability to influence ribosome assembly. RsmG is the methyltransferase responsible for the N7 methylation of G527 of 16S rRNA. Here we show that RsmG binds preferably to premature bacterial small subunit rRNA. The presence of ribosomal proteins also influences the stability of RsmG–rRNA complexes.![]()
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Affiliation(s)
- Sudeshi M Abedeera
- Department of Chemistry and Biochemistry, Kent State University Kent Ohio 44242 USA
| | - Caitlin M Hawkins
- Department of Chemistry and Biochemistry, Kent State University Kent Ohio 44242 USA
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6
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Sirichoat A, Flórez AB, Vázquez L, Buppasiri P, Panya M, Lulitanond V, Mayo B. Antibiotic Susceptibility Profiles of Lactic Acid Bacteria from the Human Vagina and Genetic Basis of Acquired Resistances. Int J Mol Sci 2020; 21:E2594. [PMID: 32276519 PMCID: PMC7178285 DOI: 10.3390/ijms21072594] [Citation(s) in RCA: 21] [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: 03/17/2020] [Revised: 04/01/2020] [Accepted: 04/07/2020] [Indexed: 12/29/2022] Open
Abstract
Lactic acid bacteria can act as reservoirs of antibiotic resistance genes that can be ultimately transferred to pathogens. The present work reports on the minimum inhibitory concentration (MIC) of 16 antibiotics to 25 LAB isolates of five Lactobacillus and one Bifidobacterium species from the human vagina. Acquired resistances were detected to kanamycin, streptomycin, chloramphenicol, gentamicin, and ampicillin. A PCR analysis of lactobacilli failed to identify genetic determinants involved in any of these resistances. Surprisingly, a tet(W) gene was detected by PCR in two Bifidobacterium bifidum strains, although they proved to be tetracycline-susceptible. In agreement with the PCR results, no acquired genes were identified in the genome of any of the Lactobacillus spp. strains sequenced. A genome analysis of B. bifidum VA07-1AN showed an insertion of two guanines in the middle of tet(W) interrupting the open reading frame. By growing the strain in the presence of tetracycline, stable tetracycline-resistant variants were obtained. An amino acid substitution in the ribosomal protein S12 (K43R) was further identified as the most likely cause of VA07-1AN being streptomycin resistance. The results of this work expand our knowledge of the resistance profiles of vaginal LAB and provide evidence for the genetic basis of some acquired resistances.
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Affiliation(s)
- Auttawit Sirichoat
- Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares, s/n, 33300 Villaviciosa, Asturias, Spain; (A.S.); (A.B.F.); (L.V.)
- Department of Microbiology and Research and Diagnostic Center for Emerging Infectious Diseases (RCEID), Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand;
| | - Ana Belén Flórez
- Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares, s/n, 33300 Villaviciosa, Asturias, Spain; (A.S.); (A.B.F.); (L.V.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Avenida de Roma s/n, 33011 Oviedo, Spain
| | - Lucía Vázquez
- Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares, s/n, 33300 Villaviciosa, Asturias, Spain; (A.S.); (A.B.F.); (L.V.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Avenida de Roma s/n, 33011 Oviedo, Spain
| | - Pranom Buppasiri
- Department of Obstetrics and Gynecology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand;
| | - Marutpong Panya
- College of Medicine and Public Health, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand;
| | - Viraphong Lulitanond
- Department of Microbiology and Research and Diagnostic Center for Emerging Infectious Diseases (RCEID), Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand;
| | - Baltasar Mayo
- Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Paseo Río Linares, s/n, 33300 Villaviciosa, Asturias, Spain; (A.S.); (A.B.F.); (L.V.)
- Instituto de Investigación Sanitaria del Principado de Asturias (ISPA), Avenida de Roma s/n, 33011 Oviedo, Spain
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7
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O'Sullivan ME, Poitevin F, Sierra RG, Gati C, Dao EH, Rao Y, Aksit F, Ciftci H, Corsepius N, Greenhouse R, Hayes B, Hunter MS, Liang M, McGurk A, Mbgam P, Obrinsky T, Pardo-Avila F, Seaberg MH, Cheng AG, Ricci AJ, DeMirci H. Aminoglycoside ribosome interactions reveal novel conformational states at ambient temperature. Nucleic Acids Res 2019; 46:9793-9804. [PMID: 30113694 PMCID: PMC6182148 DOI: 10.1093/nar/gky693] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 07/19/2018] [Indexed: 11/21/2022] Open
Abstract
The bacterial 30S ribosomal subunit is a primary antibiotic target. Despite decades of discovery, the mechanisms by which antibiotic binding induces ribosomal dysfunction are not fully understood. Ambient temperature crystallographic techniques allow more biologically relevant investigation of how local antibiotic binding site interactions trigger global subunit rearrangements that perturb protein synthesis. Here, the structural effects of 2-deoxystreptamine (paromomycin and sisomicin), a novel sisomicin derivative, N1-methyl sulfonyl sisomicin (N1MS) and the non-deoxystreptamine (streptomycin) aminoglycosides on the ribosome at ambient and cryogenic temperatures were examined. Comparative studies led to three main observations. First, individual aminoglycoside–ribosome interactions in the decoding center were similar for cryogenic versus ambient temperature structures. Second, analysis of a highly conserved GGAA tetraloop of h45 revealed aminoglycoside-specific conformational changes, which are affected by temperature only for N1MS. We report the h44–h45 interface in varying states, i.e. engaged, disengaged and in equilibrium. Third, we observe aminoglycoside-induced effects on 30S domain closure, including a novel intermediary closure state, which is also sensitive to temperature. Analysis of three ambient and five cryogenic crystallography datasets reveal a correlation between h44–h45 engagement and domain closure. These observations illustrate the role of ambient temperature crystallography in identifying dynamic mechanisms of ribosomal dysfunction induced by local drug-binding site interactions. Together, these data identify tertiary ribosomal structural changes induced by aminoglycoside binding that provides functional insight and targets for drug design.
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Affiliation(s)
- Mary E O'Sullivan
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA, USA, 94305
| | - Frédéric Poitevin
- Department of Structural Biology, Stanford University, Palo Alto, CA, USA, 94305.,Stanford PULSE Institute, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Raymond G Sierra
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Cornelius Gati
- Department of Structural Biology, Stanford University, Palo Alto, CA, USA, 94305.,Biosciences Division, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - E Han Dao
- Stanford PULSE Institute, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Yashas Rao
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Fulya Aksit
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Halilibrahim Ciftci
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Nicholas Corsepius
- Department of Structural Biology, Stanford University, Palo Alto, CA, USA, 94305
| | - Robert Greenhouse
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA, USA, 94305
| | - Brandon Hayes
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Mark S Hunter
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Mengling Liang
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Alex McGurk
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Paul Mbgam
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Trevor Obrinsky
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Fátima Pardo-Avila
- Department of Structural Biology, Stanford University, Palo Alto, CA, USA, 94305
| | - Matthew H Seaberg
- Linac Coherent Light Source, SLAC National Laboratory, Menlo Park, CA, USA, 94025
| | - Alan G Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA, USA, 94305
| | - Anthony J Ricci
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Palo Alto, CA, USA, 94305
| | - Hasan DeMirci
- Department of Structural Biology, Stanford University, Palo Alto, CA, USA, 94305.,Stanford PULSE Institute, SLAC National Laboratory, Menlo Park, CA, USA, 94025.,Biosciences Division, SLAC National Laboratory, Menlo Park, CA, USA, 94025
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8
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Resistance to UV Irradiation Caused by Inactivation of nurA and herA Genes in Thermus thermophilus. J Bacteriol 2018; 200:JB.00201-18. [PMID: 29844033 DOI: 10.1128/jb.00201-18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 05/23/2018] [Indexed: 11/20/2022] Open
Abstract
NurA and HerA are thought to be essential proteins for DNA end resection in archaeal homologous recombination systems. Thermus thermophilus, an extremely thermophilic eubacterium, has proteins that exhibit significant sequence similarity to archaeal NurA and HerA. To unveil the cellular function of NurA and HerA in T. thermophilus, we performed phenotypic analysis of disruptant mutants of nurA and herA with or without DNA-damaging agents. The nurA and herA genes were not essential for survival, and their deletion had no effect on cell growth and genome integrity. Unexpectedly, these disruptants of T. thermophilus showed increased resistance to UV irradiation and mitomycin C treatment. Further, these disruptants and the wild type displayed no difference in sensitivity to oxidative stress and a DNA replication inhibitor. T. thermophilus NurA had nuclease activity, and HerA had ATPase. The overexpression of loss-of-function mutants of nurA and herA in the respective disruptants showed no complementation, suggesting their enzymatic activities were involved in the UV sensitivity. In addition, T. thermophilus NurA and HerA interacted with each other in vitro and in vivo, forming a complex with 2:6 stoichiometry. These results suggest that the NurA-HerA complex has an architecture similar to that of archaeal counterparts but that it impairs, rather than promotes, the repair of photoproducts and DNA cross-links in T. thermophilus cells. This cellular function is distinctly different from that of archaeal NurA and HerA.IMPORTANCE Many nucleases and helicases are engaged in homologous recombination-mediated DNA repair. Previous in vitro analyses in archaea indicated that NurA and HerA are the recombination-related nuclease and helicase. However, their cellular function had not been fully understood, especially in bacterial cells. In this study, we performed in vivo analyses to address the cellular function of nurA and herA in an extremely thermophilic bacterium, Thermus thermophilus As a result, T. thermophilus NurA and HerA exhibited an interfering effect on the repair of several instances of DNA damage in the cell, which is in contrast to the results in archaea. This finding will facilitate our understanding of the diverse cellular functions of the recombination-related nucleases and helicases.
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9
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Flórez AB, Mayo B. Antibiotic Resistance-Susceptibility Profiles of Streptococcus thermophilus Isolated from Raw Milk and Genome Analysis of the Genetic Basis of Acquired Resistances. Front Microbiol 2017; 8:2608. [PMID: 29312272 PMCID: PMC5744436 DOI: 10.3389/fmicb.2017.02608] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 12/14/2017] [Indexed: 12/26/2022] Open
Abstract
The food chain is thought to play an important role in the transmission of antibiotic resistances from commensal and beneficial bacteria to pathogens. Streptococcus thermophilus is a lactic acid bacterium of major importance as a starter for the dairy industry. This study reports the minimum inhibitory concentration (MIC) of 16 representative antimicrobial agents to 41 isolates of S. thermophilus derived from raw milk. Strains showing resistance to tetracycline (seven), erythromycin and clindamycin (two), and streptomycin and neomycin (one) were found. PCR amplification identified tet(S) in all the tetracycline-resistant strains, and ermB in the two erythromycin/clindamycin-resistant strains. Hybridisation experiments suggested each resistance gene to be located in the chromosome with a similar genetic organization. Five antibiotic-resistant strains -two resistant to tetracycline (St-2 and St-9), two resistant to erythromycin/clindamycin (St-5 and St-6), and one resistant to streptomycin/neomycin (St-10)- were subjected to genome sequencing and analysis. The tet(S) gene was identified in small contigs of 3.2 and 3.7 kbp in St-2 and St-9, respectively, flanked by truncated copies of insertion sequence (IS) elements. Similarly, ermB in St-6 and St-5 was found in contigs of 1.6 and 28.1 kbp, respectively. Sequence analysis and comparison of the largest contig showed it to contain three segments (21.9, 3.7, and 1.4 kbp long) highly homologous to non-collinear sequences of pRE25 from Enterococcus faecalis. These segments contained the ermB gene, a transference module with an origin of transfer (oriT) plus 15 open reading frames encoding proteins involved in conjugation, and modules for plasmid replication and segregation. Homologous stretches were separated by short, IS-related sequences, resembling the genetic organization of the integrative and conjugative elements (ICEs) found in Streptococcus species. No gene known to provide aminoglycoside resistance was seen in St-10. Four strain-specific amino acid substitutions in the RsmG methyltransferase were scored in this strain; these might be associated to its streptomycin/neomycin resistance. Under yogurt manufacturing and storage conditions, no transfer of either tet(S) or ermB from S. thermophilus to L. delbrueckii was detected. The present results contribute toward characterisation of the antibiotic resistance profiles in S. thermophilus, provide evidence for the genetic basis of acquired resistances and deepen on their transference capability.
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Affiliation(s)
| | - Baltasar Mayo
- Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (CSIC), Paseo Río Linares s/n, Asturias, Spain
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10
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Seelam PP, Sharma P, Mitra A. Structural landscape of base pairs containing post-transcriptional modifications in RNA. RNA (NEW YORK, N.Y.) 2017; 23:847-859. [PMID: 28341704 PMCID: PMC5435857 DOI: 10.1261/rna.060749.117] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 03/23/2017] [Indexed: 05/20/2023]
Abstract
Base pairs involving post-transcriptionally modified nucleobases are believed to play important roles in a wide variety of functional RNAs. Here we present our attempts toward understanding the structural and functional role of naturally occurring modified base pairs using a combination of X-ray crystal structure database analysis, sequence analysis, and advanced quantum chemical methods. Our bioinformatics analysis reveals that despite their presence in all major secondary structural elements, modified base pairs are most prevalent in tRNA crystal structures and most commonly involve guanine or uridine modifications. Further, analysis of tRNA sequences reveals additional examples of modified base pairs at structurally conserved tRNA regions and highlights the conservation patterns of these base pairs in three domains of life. Comparison of structures and binding energies of modified base pairs with their unmodified counterparts, using quantum chemical methods, allowed us to classify the base modifications in terms of the nature of their electronic structure effects on base-pairing. Analysis of specific structural contexts of modified base pairs in RNA crystal structures revealed several interesting scenarios, including those at the tRNA:rRNA interface, antibiotic-binding sites on the ribosome, and the three-way junctions within tRNA. These scenarios, when analyzed in the context of available experimental data, allowed us to correlate the occurrence and strength of modified base pairs with their specific functional roles. Overall, our study highlights the structural importance of modified base pairs in RNA and points toward the need for greater appreciation of the role of modified bases and their interactions, in the context of many biological processes involving RNA.
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Affiliation(s)
- Preethi P Seelam
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology Hyderabad (IIIT-H), Gachibowli, Hyderabad, Telangana 500032, India
| | - Purshotam Sharma
- Computational Biochemistry Laboratory, Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University, Chandigarh 160014, India
| | - Abhijit Mitra
- Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology Hyderabad (IIIT-H), Gachibowli, Hyderabad, Telangana 500032, India
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11
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Resistance mutations generate divergent antibiotic susceptibility profiles against translation inhibitors. Proc Natl Acad Sci U S A 2016; 113:8188-93. [PMID: 27382179 DOI: 10.1073/pnas.1605127113] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mutations conferring resistance to translation inhibitors often alter the structure of rRNA. Reduced susceptibility to distinct structural antibiotic classes may, therefore, emerge when a common ribosomal binding site is perturbed, which significantly reduces the clinical utility of these agents. The translation inhibitors negamycin and tetracycline interfere with tRNA binding to the aminoacyl-tRNA site on the small 30S ribosomal subunit. However, two negamycin resistance mutations display unexpected differential antibiotic susceptibility profiles. Mutant U1060A in 16S Escherichia coli rRNA is resistant to both antibiotics, whereas mutant U1052G is simultaneously resistant to negamycin and hypersusceptible to tetracycline. Using a combination of microbiological, biochemical, single-molecule fluorescence transfer experiments, and X-ray crystallography, we define the specific structural defects in the U1052G mutant 70S E. coli ribosome that explain its divergent negamycin and tetracycline susceptibility profiles. Unexpectedly, the U1052G mutant ribosome possesses a second tetracycline binding site that correlates with its hypersusceptibility. The creation of a previously unidentified antibiotic binding site raises the prospect of identifying similar phenomena in antibiotic-resistant pathogens in the future.
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Jiang J, Seo H, Chow CS. Post-transcriptional Modifications Modulate rRNA Structure and Ligand Interactions. Acc Chem Res 2016; 49:893-901. [PMID: 27064497 DOI: 10.1021/acs.accounts.6b00014] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Post-transcriptional modifications play important roles in modulating the functions of RNA species. The presence of modifications in RNA may directly alter its interactions with binding partners or cause structural changes that indirectly affect ligand recognition. Given the rapidly growing list of modifications identified in noncoding and mRNAs associated with human disease, as well as the dynamic control over modifications involved in various physiological processes, it is imperative to understand RNA structural modulation by these modifications. Among the RNA species, rRNAs provide numerous examples of modification types located in differing sequence and structural contexts. In addition, the modified rRNA motifs participate in a wide variety of ligand interactions, including those with RNA, protein, and small molecules. In fact, several classes of antibiotics exert their effects on protein synthesis by binding to functionally important and highly modified regions of the rRNAs. These RNA regions often display conservation in sequence, secondary structure, tertiary interactions, and modifications, trademarks of ideal drug-targeting sites. Furthermore, ligand interactions with such regions often favor certain modification-induced conformational states of the RNA. Our laboratory has employed a combination of biophysical methods such as nuclear magnetic resonance spectroscopy (NMR), circular dichroism, and UV melting to study rRNA modifications in functionally important motifs, including helix 31 (h31) and helix h44 (h44) of the small subunit rRNA and helix 69 (H69) of the large subunit rRNA. The modified RNA oligonucleotides used in these studies were generated by solid-phase synthesis with a variety of phosphoramidite chemistries. The natural modifications were shown to impact thermal stability, dynamic behavior, and tertiary structures of the RNAs, with additive or cooperative effects occurring with multiple, clustered modifications. Taking advantage of the structural diversity offered by specific modifications in the chosen rRNA motifs, phage display was used to select peptides that bind with moderate (low micromolar) affinity and selectivity to modified h31, h44, and H69. Interactions between peptide ligands and RNAs were monitored by biophysical methods, including electrospray ionization mass spectrometry (ESI-MS), NMR, and surface plasmon resonance (SPR). The peptides compare well with natural compounds such as aminoglycosides in their binding affinities to the modified rRNA constructs. Some candidates were shown to exhibit specificity toward different modification states of the rRNA motifs. The selected peptides may be further optimized for improved RNA targeting or used in screening assays for new drug candidates. In this Account, we hope to stimulate interest in bioorganic and biophysical approaches, which may be used to deepen our understanding of other functionally important, naturally modified RNAs beyond the rRNAs.
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Affiliation(s)
- Jun Jiang
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Hyosuk Seo
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Christine S. Chow
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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