1
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Anderson AJG, Morrell B, Lopez Campos G, Valvano MA. Distribution and diversity of type VI secretion system clusters in Enterobacter bugandensis and Enterobacter cloacae. Microb Genom 2023; 9:001148. [PMID: 38054968 PMCID: PMC10763514 DOI: 10.1099/mgen.0.001148] [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: 09/06/2023] [Accepted: 11/16/2023] [Indexed: 12/07/2023] Open
Abstract
Gram-negative bacteria use type VI secretion systems (T6SSs) to antagonize neighbouring cells. Although primarily involved in bacterial competition, the T6SS is also implicated in pathogenesis, biofilm formation and ion scavenging. Enterobacter species belong to the ESKAPE pathogens, and while their antibiotic resistance has been well studied, less is known about their pathogenesis. Here, we investigated the distribution and diversity of T6SS components in isolates of two clinically relevant Enterobacter species, E. cloacae and E. bugandensis. T6SS clusters are grouped into four types (T6SSi-T6SSiv), of which type i can be further divided into six subtypes (i1, i2, i3, i4a, i4b, i5). Analysis of a curated dataset of 31 strains demonstrated that most of them encode T6SS clusters belonging to the T6SSi type. All T6SS-positive strains possessed a conserved i3 cluster, and many harboured one or two additional i2 clusters. These clusters were less conserved, and some strains displayed evidence of deletion. We focused on a pathogenic E. bugandensis clinical isolate for comprehensive in silico effector prediction, with comparative analyses across the 31 isolates. Several new effector candidates were identified, including an evolved VgrG with a metallopeptidase domain and a Tse6-like protein. Additional effectors included an anti-eukaryotic catalase (KatN), M23 peptidase, PAAR and VgrG proteins. Our findings highlight the diversity of Enterobacter T6SSs and reveal new putative effectors that may be important for the interaction of these species with neighbouring cells and their environment.
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Affiliation(s)
- Amy J. G. Anderson
- Wellcome-Wolfson Institute for Experimental Medicine, Queen’s University Belfast, Belfast, BT9 7BL, UK
| | - Becca Morrell
- Wellcome-Wolfson Institute for Experimental Medicine, Queen’s University Belfast, Belfast, BT9 7BL, UK
| | - Guillermo Lopez Campos
- Wellcome-Wolfson Institute for Experimental Medicine, Queen’s University Belfast, Belfast, BT9 7BL, UK
| | - Miguel A. Valvano
- Wellcome-Wolfson Institute for Experimental Medicine, Queen’s University Belfast, Belfast, BT9 7BL, UK
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2
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Gao M, Li P, Su Z, Huang Y. Topological frustration leading to backtracking in a coupled folding-binding process. Phys Chem Chem Phys 2022; 24:2630-2637. [PMID: 35029261 DOI: 10.1039/d1cp04927e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Intrinsically disordered proteins (IDPs) are abundant in all species. Their discovery challenges the traditional "sequence-structure-function" paradigm of protein science because IDPs play important roles in various biological processes without preformed folded structures. Bioinformatic analysis reveals that the intrinsically conformational disorder of IDPs as well as their conformational transition upon binding to their targets is encoded by their amino acid sequences. The rRNase domain of colicin E3 and the immunity protein Im3 are a pair of proteins involved in bacterial survival. While the N-terminal segment and the central segment of E3 make comparable intermolecular contacts with Im3 in the bound state, binding of E3 with Im3 is dominantly triggered by the central segment of E3. In this work, to further investigate the binding mechanism of disordered E3 with Im3, we performed systematic free energy and transition path analysis through coarse-grained molecular dynamics simulations. We observed backtracking of the N-terminal segment of E3 in the binding process, whose occurrence depends on salt concentration. Conformational analysis revealed that initial binding of the N-terminal segment of E3 to Im3 usually leads to misorientation of a central hairpin of E3 on Im3, which generates topological frustration and results in backtracking of the N-terminal segment. Our results not only provide deeper mechanistic insights into the coupled folding-binding process of the E3/Im3 complex, but also suggest that topological frustration could be present in the coupled folding-binding process of IDPs and play an important role in regulating the binding transition pathways.
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Affiliation(s)
- Meng Gao
- Key Laboratory of Industrial Fermentation (Ministry of Education), Hubei University of Technology, Wuhan 430068, China.
- Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Department of Biological Engineering, Hubei University of Technology, Wuhan 430068, China
| | - Ping Li
- Key Laboratory of Industrial Fermentation (Ministry of Education), Hubei University of Technology, Wuhan 430068, China.
- Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Department of Biological Engineering, Hubei University of Technology, Wuhan 430068, China
| | - Zhengding Su
- Key Laboratory of Industrial Fermentation (Ministry of Education), Hubei University of Technology, Wuhan 430068, China.
- Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Department of Biological Engineering, Hubei University of Technology, Wuhan 430068, China
| | - Yongqi Huang
- Key Laboratory of Industrial Fermentation (Ministry of Education), Hubei University of Technology, Wuhan 430068, China.
- Hubei Key Laboratory of Industrial Microbiology, Hubei University of Technology, Wuhan, China
- National "111" Center for Cellular Regulation and Molecular Pharmaceutics, Department of Biological Engineering, Hubei University of Technology, Wuhan 430068, China
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3
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Ruhe ZC, Low DA, Hayes CS. Polymorphic Toxins and Their Immunity Proteins: Diversity, Evolution, and Mechanisms of Delivery. Annu Rev Microbiol 2020; 74:497-520. [PMID: 32680451 DOI: 10.1146/annurev-micro-020518-115638] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
All bacteria must compete for growth niches and other limited environmental resources. These existential battles are waged at several levels, but one common strategy entails the transfer of growth-inhibitory protein toxins between competing cells. These antibacterial effectors are invariably encoded with immunity proteins that protect cells from intoxication by neighboring siblings. Several effector classes have been described, each designed to breach the cell envelope of target bacteria. Although effector architectures and export pathways tend to be clade specific, phylogenetically distant species often deploy closely related toxin domains. Thus, diverse competition systems are linked through a common reservoir of toxin-immunity pairs that is shared via horizontal gene transfer. These toxin-immunity protein pairs are extraordinarily diverse in sequence, and this polymorphism underpins an important mechanism of self/nonself discrimination in bacteria. This review focuses on the structures, functions, and delivery mechanisms of polymorphic toxin effectors that mediate bacterial competition.
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Affiliation(s)
- Zachary C Ruhe
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA;
| | - David A Low
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106, USA; .,Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106, USA
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4
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Smolkin B, Khononov A, Pieńko T, Shavit M, Belakhov V, Trylska J, Baasov T. Towards Catalytic Antibiotics: Redesign of Aminoglycosides To Catalytically Disable Bacterial Ribosomes. Chembiochem 2018; 20:247-259. [DOI: 10.1002/cbic.201800549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 11/20/2018] [Indexed: 12/30/2022]
Affiliation(s)
- Boris Smolkin
- The Edith and Joseph Fischer Enzyme Inhibitors Laboratory; Schulich Faculty of Chemistry; Technion-Israel Institute of Technology; Haifa 3200003 Israel
| | - Alina Khononov
- The Edith and Joseph Fischer Enzyme Inhibitors Laboratory; Schulich Faculty of Chemistry; Technion-Israel Institute of Technology; Haifa 3200003 Israel
| | - Tomasz Pieńko
- Centre of New Technologies; University of Warsaw; Banacha 2c 02-097 Warsaw Poland
- Department of Drug Chemistry; Faculty of Pharmacy with the Laboratory Medicine Division; Medical University of Warsaw; Banacha 1a 02-097 Warsaw Poland
| | - Michal Shavit
- The Edith and Joseph Fischer Enzyme Inhibitors Laboratory; Schulich Faculty of Chemistry; Technion-Israel Institute of Technology; Haifa 3200003 Israel
| | - Valery Belakhov
- The Edith and Joseph Fischer Enzyme Inhibitors Laboratory; Schulich Faculty of Chemistry; Technion-Israel Institute of Technology; Haifa 3200003 Israel
| | - Joanna Trylska
- Centre of New Technologies; University of Warsaw; Banacha 2c 02-097 Warsaw Poland
| | - Timor Baasov
- The Edith and Joseph Fischer Enzyme Inhibitors Laboratory; Schulich Faculty of Chemistry; Technion-Israel Institute of Technology; Haifa 3200003 Israel
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5
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Kryshtafovych A, Albrecht R, Baslé A, Bule P, Caputo AT, Carvalho AL, Chao KL, Diskin R, Fidelis K, Fontes CMGA, Fredslund F, Gilbert HJ, Goulding CW, Hartmann MD, Hayes CS, Herzberg O, Hill JC, Joachimiak A, Kohring GW, Koning RI, Lo Leggio L, Mangiagalli M, Michalska K, Moult J, Najmudin S, Nardini M, Nardone V, Ndeh D, Nguyen TH, Pintacuda G, Postel S, van Raaij MJ, Roversi P, Shimon A, Singh AK, Sundberg EJ, Tars K, Zitzmann N, Schwede T. Target highlights from the first post-PSI CASP experiment (CASP12, May-August 2016). Proteins 2018; 86 Suppl 1:27-50. [PMID: 28960539 PMCID: PMC5820184 DOI: 10.1002/prot.25392] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 09/19/2017] [Accepted: 09/25/2017] [Indexed: 12/27/2022]
Abstract
The functional and biological significance of the selected CASP12 targets are described by the authors of the structures. The crystallographers discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP12 experiment.
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Affiliation(s)
- Andriy Kryshtafovych
- Genome Center, University of California, Davis, 451 Health Sciences Drive, Davis, California, 95616
| | - Reinhard Albrecht
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, 72076, Germany
| | - Arnaud Baslé
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Pedro Bule
- CIISA - Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477, Portugal, Lisboa
| | - Alessandro T Caputo
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England, United Kingdom
| | - Ana Luisa Carvalho
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Cien⁁cias e Tecnologia, Universidade Nova de Lisboa, Caparica, 2829-516, Portugal
| | - Kinlin L Chao
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland, 20850
| | - Ron Diskin
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Krzysztof Fidelis
- Genome Center, University of California, Davis, 451 Health Sciences Drive, Davis, California, 95616
| | - Carlos M G A Fontes
- CIISA - Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477, Portugal, Lisboa
| | - Folmer Fredslund
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Harry J Gilbert
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Celia W Goulding
- Department of Molecular Biology and Biochemistry/Pharmaceutical Sciences, University of California Irvine, Irvine, California, 92697
| | - Marcus D Hartmann
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Tübingen, 72076, Germany
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology/Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, California, 93106
| | - Osnat Herzberg
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland, 20850
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, 20742
| | - Johan C Hill
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England, United Kingdom
| | - Andrzej Joachimiak
- Argonne National Laboratory, Midwest Center for Structural Genomics/Structural Biology Center, Biosciences Division, Argonne, Illinois, 60439
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, 60637
| | - Gert-Wieland Kohring
- Microbiology, Saarland University, Campus Building A1.5, Saarbrücken, Saarland, D-66123, Germany
| | - Roman I Koning
- Netherlands Centre for Electron Nanoscopy, Institute of Biology Leiden, Leiden University, 2333, CC Leiden, The Netherlands
- Department of Molecular Cell Biology, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
| | - Leila Lo Leggio
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | - Marco Mangiagalli
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, 20126, Italy
| | - Karolina Michalska
- Argonne National Laboratory, Midwest Center for Structural Genomics/Structural Biology Center, Biosciences Division, Argonne, Illinois, 60439
| | - John Moult
- Department of Cell Biology and Molecular genetics, University of Maryland, 9600 Gudelsky Drive, Institute for Bioscience and Biotechnology Research, Rockville, Maryland, 20850
| | - Shabir Najmudin
- CIISA - Faculdade de Medicina Veterinária, Universidade de Lisboa, Avenida da Universidade Técnica, 1300-477, Portugal, Lisboa
| | - Marco Nardini
- Department of Biosciences, University of Milano, Milano, 20133, Italy
| | - Valentina Nardone
- Department of Biosciences, University of Milano, Milano, 20133, Italy
| | - Didier Ndeh
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, United Kingdom
| | - Thanh-Hong Nguyen
- Department of Macromolecular Structures, Centro Nacional de Biotecnologia (CSIC), calle Darwin 3, Madrid, 28049, Spain
| | - Guido Pintacuda
- Université de Lyon, Centre de RMN à Très Hauts Champs, Institut des Sciences Analytiques (UMR 5280 - CNRS, ENS Lyon, UCB Lyon 1), Villeurbanne, 69100, France
| | - Sandra Postel
- University of Maryland School of Medicine, Institute of Human Virology, Baltimore, Maryland, 21201
| | - Mark J van Raaij
- Department of Macromolecular Structures, Centro Nacional de Biotecnologia (CSIC), calle Darwin 3, Madrid, 28049, Spain
| | - Pietro Roversi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England, United Kingdom
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, University Road, Leicester, LE1 7RN, UK
| | - Amir Shimon
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Abhimanyu K Singh
- School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, United Kingdom
| | - Eric J Sundberg
- Department of Medicine and Department of Microbiology and Immunology, University of Maryland School of Medicine, Institute of Human Virology, Baltimore, Maryland, 21201
| | - Kaspars Tars
- Latvian Biomedical Research and Study Center, Rātsupītes 1, Riga, LV1067, Latvia
- Faculty of Biology, Department of Molecular Biology, University of Latvia, Jelgavas 1, Riga, LV-1004, Latvia
| | - Nicole Zitzmann
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, England, United Kingdom
| | - Torsten Schwede
- Biozentrum/SIB Swiss Institute of Bioinformatics, Klingelbergstrasse 50, Basel, 4056, Switzerland
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6
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Németh E, Balogh RK, Borsos K, Czene A, Thulstrup PW, Gyurcsik B. Intrinsic protein disorder could be overlooked in cocrystallization conditions: An SRCD case study. Protein Sci 2016; 25:1977-1988. [PMID: 27508941 DOI: 10.1002/pro.3010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 08/08/2016] [Indexed: 12/21/2022]
Abstract
X-ray diffractometry dominates protein studies, as it can provide 3D structures of these diverse macromolecules or their molecular complexes with interacting partners: substrates, inhibitors, and/or cofactors. Here, we show that under cocrystallization conditions the results could reflect induced protein folds instead of the (partially) disordered original structures. The analysis of synchrotron radiation circular dichroism spectra revealed that the Im7 immunity protein stabilizes the native-like solution structure of unfolded NColE7 nuclease mutants via complex formation. This is consistent with the fact that among the several available crystal structures with its inhibitor or substrate, all NColE7 structures are virtually the same. Our results draw attention to the possible structural consequence of protein modifications, which is often hidden by compensational effects of intermolecular interactions. The growing evidence on the importance of protein intrinsic disorder thus, demands more extensive complementary experiments in solution phase with the unligated form of the protein of interest.
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Affiliation(s)
- Eszter Németh
- Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, 6720, Hungary.,MTA-SZTE, Bioinorganic Chemistry Research Group, Hungarian Academy of Sciences, Szeged, 6720, Hungary
| | - Ria K Balogh
- Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, 6720, Hungary
| | - Katalin Borsos
- Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, 6720, Hungary
| | - Anikó Czene
- MTA-SZTE, Bioinorganic Chemistry Research Group, Hungarian Academy of Sciences, Szeged, 6720, Hungary
| | - Peter W Thulstrup
- Department of Chemistry, University of Copenhagen, Copenhagen, 2100, Denmark
| | - Béla Gyurcsik
- Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, 6720, Hungary. .,MTA-SZTE, Bioinorganic Chemistry Research Group, Hungarian Academy of Sciences, Szeged, 6720, Hungary.
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7
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Morse RP, Willett JLE, Johnson PM, Zheng J, Credali A, Iniguez A, Nowick JS, Hayes CS, Goulding CW. Diversification of β-Augmentation Interactions between CDI Toxin/Immunity Proteins. J Mol Biol 2015; 427:3766-84. [PMID: 26449640 DOI: 10.1016/j.jmb.2015.09.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/20/2015] [Accepted: 09/22/2015] [Indexed: 01/03/2023]
Abstract
Contact-dependent growth inhibition (CDI) is a widespread mechanism of inter-bacterial competition mediated by the CdiB/CdiA family of two-partner secretion proteins. CdiA effectors carry diverse C-terminal toxin domains (CdiA-CT), which are delivered into neighboring target cells to inhibit growth. CDI(+) bacteria also produce CdiI immunity proteins that bind specifically to cognate CdiA-CT toxins and protect the cell from auto-inhibition. Here, we compare the structures of homologous CdiA-CT/CdiI complexes from Escherichia coli EC869 and Yersinia pseudotuberculosis YPIII to explore the evolution of CDI toxin/immunity protein interactions. Both complexes share an unusual β-augmentation interaction, in which the toxin domain extends a β-hairpin into the immunity protein to complete a six-stranded anti-parallel sheet. However, the specific contacts differ substantially between the two complexes. The EC869 β-hairpin interacts mainly through direct H-bond and ion-pair interactions, whereas the YPIII β-hairpin pocket contains more hydrophobic contacts and a network of bridging water molecules. In accord with these differences, we find that each CdiI protein only protects target bacteria from its cognate CdiA-CT toxin. The compact β-hairpin binding pocket within the immunity protein represents a tractable system for the rationale design of small molecules to block CdiA-CT/CdiI complex formation. We synthesized a macrocyclic peptide mimic of the β-hairpin from EC869 toxin and solved its structure in complex with cognate immunity protein. These latter studies suggest that small molecules could potentially be used to disrupt CDI toxin/immunity complexes.
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Affiliation(s)
- Robert P Morse
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Julia L E Willett
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Parker M Johnson
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Jing Zheng
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Alfredo Credali
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Angelina Iniguez
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - James S Nowick
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA; Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Celia W Goulding
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA; Department of Pharmaceutical Sciences, University of California, Irvine, Irvine, CA 92697, USA.
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8
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Papadakos G, Sharma A, Lancaster LE, Bowen R, Kaminska R, Leech AP, Walker D, Redfield C, Kleanthous C. Consequences of Inducing Intrinsic Disorder in a High-Affinity Protein–Protein Interaction. J Am Chem Soc 2015; 137:5252-5. [DOI: 10.1021/ja512607r] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Grigorios Papadakos
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Amit Sharma
- Astbury
Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Lorna E. Lancaster
- School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln LN6 7TS, United Kingdom
| | - Rebecca Bowen
- Department of Biology, University of York, Heslington Road, York YO10 5DD, United Kingdom
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Andrew P. Leech
- Department of Biology, University of York, Heslington Road, York YO10 5DD, United Kingdom
| | - Daniel Walker
- Institute
of Infection, Immunity and Inflammation, College of Medical, Veterinary
and Life Sciences, University of Glasgow, Glasgow G12 8AT, United Kingdom
| | - Christina Redfield
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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9
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Kim YC, Tarr AW, Penfold CN. Colicin import into E. coli cells: a model system for insights into the import mechanisms of bacteriocins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1717-31. [PMID: 24746518 DOI: 10.1016/j.bbamcr.2014.04.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/04/2014] [Accepted: 04/06/2014] [Indexed: 01/03/2023]
Abstract
Bacteriocins are a diverse group of ribosomally synthesized protein antibiotics produced by most bacteria. They range from small lanthipeptides produced by lactic acid bacteria to much larger multi domain proteins of Gram negative bacteria such as the colicins from Escherichia coli. For activity bacteriocins must be released from the producing cell and then bind to the surface of a sensitive cell to instigate the import process leading to cell death. For over 50years, colicins have provided a working platform for elucidating the structure/function studies of bacteriocin import and modes of action. An understanding of the processes that contribute to the delivery of a colicin molecule across two lipid membranes of the cell envelope has advanced our knowledge of protein-protein interactions (PPI), protein-lipid interactions and the role of order-disorder transitions of protein domains pertinent to protein transport. In this review, we provide an overview of the arrangement of genes that controls the synthesis and release of the mature protein. We examine the uptake processes of colicins from initial binding and sequestration of binding partners to crossing of the outer membrane, and then discuss the translocation of colicins through the cell periplasm and across the inner membrane to their cytotoxic site of action. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Young Chan Kim
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK
| | - Alexander W Tarr
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK
| | - Christopher N Penfold
- School of Life Sciences, University of Nottingham, Queens Medical Centre, Nottingham, NG7 2UH, UK.
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10
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Beck CM, Morse RP, Cunningham DA, Iniguez A, Low DA, Goulding CW, Hayes CS. CdiA from Enterobacter cloacae delivers a toxic ribosomal RNase into target bacteria. Structure 2014; 22:707-18. [PMID: 24657090 DOI: 10.1016/j.str.2014.02.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 02/11/2014] [Accepted: 02/16/2014] [Indexed: 12/31/2022]
Abstract
Contact-dependent growth inhibition (CDI) is one mechanism of inter-bacterial competition. CDI(+) cells export large CdiA effector proteins, which carry a variety of C-terminal toxin domains (CdiA-CT). CdiA-CT toxins are specifically neutralized by cognate CdiI immunity proteins to protect toxin-producing cells from autoinhibition. Here, we use structure determination to elucidate the activity of a CDI toxin from Enterobacter cloacae (ECL). The structure of CdiA-CT(ECL) resembles the C-terminal nuclease domain of colicin E3, which cleaves 16S ribosomal RNA to disrupt protein synthesis. In accord with this structural homology, we show that CdiA-CT(ECL) uses the same nuclease activity to inhibit bacterial growth. Surprisingly, although colicin E3 and CdiA(ECL) carry equivalent toxin domains, the corresponding immunity proteins are unrelated in sequence, structure, and toxin-binding site. Together, these findings reveal unexpected diversity among 16S rRNases and suggest that these nucleases are robust and versatile payloads for a variety of toxin-delivery platforms.
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Affiliation(s)
- Christina M Beck
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Robert P Morse
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - David A Cunningham
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Angelina Iniguez
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA
| | - David A Low
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA; Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA
| | - Celia W Goulding
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA; Department of Pharmaceutical Sciences, University of California, Irvine, Irvine, CA 92697, USA
| | - Christopher S Hayes
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA; Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, CA 93106-9625, USA.
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11
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Singh J. Role of D535 and H538 in endogenous toxicity of xenocin from Xenorhabdus nematophila. FEMS Microbiol Lett 2012; 338:147-54. [PMID: 23227808 DOI: 10.1111/1574-6968.12045] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Accepted: 10/29/2012] [Indexed: 11/29/2022] Open
Abstract
Bacteriocins are the toxic proteins produced by bacteria under stress condition to inhibit the growth of closely related bacterial strain(s). In our earlier study, purified recombinant xenocin-immunity protein complex from Xenorhabdus nematophila showed detrimental effect on six different insect gut residing bacteria. In this study, endogenous toxicity assay with xcinA and its catalytic domain under tightly regulated ara promoter was performed. Multiple sequence alignment and homology modelling revealed six conserved amino acid residues in the catalytic domain of xenocin. Site-directed mutagenesis was performed in all the conserved residues, followed growth profile analysis of all the mutants by endogenous toxicity assay. Among the six different conserved sites in catalytic domain of xenocin, we have identified one position where mutation resulted in no measurable reduction in the endogenous toxicity (K564), three positions with measurable reduction in the endogenous toxicity (E542, H551 and R570) and two positions where mutation caused a significant reduction in the toxicity (D535 and H538). Endogenous toxicity assay is validated by in vitro RNA degradation assay. Structural integrity of purified recombinant proteins was confirmed through circular dichroism and fluorescence spectroscopy. Our results indicate that D535 and H538 act as the acid-base pair for RNA hydrolysis.
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Affiliation(s)
- Jitendra Singh
- School of Biotechnology, Gautam Buddha University, Greater Noida, Uttar Pradesh, India
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12
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Loper JE, Hassan KA, Mavrodi DV, Davis EW, Lim CK, Shaffer BT, Elbourne LDH, Stockwell VO, Hartney SL, Breakwell K, Henkels MD, Tetu SG, Rangel LI, Kidarsa TA, Wilson NL, van de Mortel JE, Song C, Blumhagen R, Radune D, Hostetler JB, Brinkac LM, Durkin AS, Kluepfel DA, Wechter WP, Anderson AJ, Kim YC, Pierson LS, Pierson EA, Lindow SE, Kobayashi DY, Raaijmakers JM, Weller DM, Thomashow LS, Allen AE, Paulsen IT. Comparative genomics of plant-associated Pseudomonas spp.: insights into diversity and inheritance of traits involved in multitrophic interactions. PLoS Genet 2012; 8:e1002784. [PMID: 22792073 PMCID: PMC3390384 DOI: 10.1371/journal.pgen.1002784] [Citation(s) in RCA: 398] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/10/2012] [Indexed: 12/11/2022] Open
Abstract
We provide here a comparative genome analysis of ten strains within the Pseudomonas fluorescens group including seven new genomic sequences. These strains exhibit a diverse spectrum of traits involved in biological control and other multitrophic interactions with plants, microbes, and insects. Multilocus sequence analysis placed the strains in three sub-clades, which was reinforced by high levels of synteny, size of core genomes, and relatedness of orthologous genes between strains within a sub-clade. The heterogeneity of the P. fluorescens group was reflected in the large size of its pan-genome, which makes up approximately 54% of the pan-genome of the genus as a whole, and a core genome representing only 45–52% of the genome of any individual strain. We discovered genes for traits that were not known previously in the strains, including genes for the biosynthesis of the siderophores achromobactin and pseudomonine and the antibiotic 2-hexyl-5-propyl-alkylresorcinol; novel bacteriocins; type II, III, and VI secretion systems; and insect toxins. Certain gene clusters, such as those for two type III secretion systems, are present only in specific sub-clades, suggesting vertical inheritance. Almost all of the genes associated with multitrophic interactions map to genomic regions present in only a subset of the strains or unique to a specific strain. To explore the evolutionary origin of these genes, we mapped their distributions relative to the locations of mobile genetic elements and repetitive extragenic palindromic (REP) elements in each genome. The mobile genetic elements and many strain-specific genes fall into regions devoid of REP elements (i.e., REP deserts) and regions displaying atypical tri-nucleotide composition, possibly indicating relatively recent acquisition of these loci. Collectively, the results of this study highlight the enormous heterogeneity of the P. fluorescens group and the importance of the variable genome in tailoring individual strains to their specific lifestyles and functional repertoire. We sequenced the genomes of seven strains of the Pseudomonas fluorescens group that colonize plant surfaces and function as biological control agents, protecting plants from disease. In this study, we demonstrated the genomic diversity of the group by comparing these strains to each other and to three other strains that were sequenced previously. Only about half of the genes in each strain are present in all of the other strains, and each strain has hundreds of unique genes that are not present in the other genomes. We mapped the genes that contribute to biological control in each genome and found that most of the biological control genes are in the variable regions of the genome, which are not shared by all of the other strains. This finding is consistent with our knowledge of the distinctive biology of each strain. Finally, we looked for new genes that are likely to confer antimicrobial traits needed to suppress plant pathogens, but have not been identified previously. In each genome, we discovered many of these new genes, which provide avenues for future discovery of new traits with the potential to manage plant diseases in agriculture or natural ecosystems.
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Affiliation(s)
- Joyce E Loper
- Agricultural Research Service, US Department of Agriculture, Corvallis, Oregon, United States of America.
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13
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Zhang D, de Souza RF, Anantharaman V, Iyer LM, Aravind L. Polymorphic toxin systems: Comprehensive characterization of trafficking modes, processing, mechanisms of action, immunity and ecology using comparative genomics. Biol Direct 2012; 7:18. [PMID: 22731697 PMCID: PMC3482391 DOI: 10.1186/1745-6150-7-18] [Citation(s) in RCA: 360] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 05/31/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Proteinaceous toxins are observed across all levels of inter-organismal and intra-genomic conflicts. These include recently discovered prokaryotic polymorphic toxin systems implicated in intra-specific conflicts. They are characterized by a remarkable diversity of C-terminal toxin domains generated by recombination with standalone toxin-coding cassettes. Prior analysis revealed a striking diversity of nuclease and deaminase domains among the toxin modules. We systematically investigated polymorphic toxin systems using comparative genomics, sequence and structure analysis. RESULTS Polymorphic toxin systems are distributed across all major bacterial lineages and are delivered by at least eight distinct secretory systems. In addition to type-II, these include type-V, VI, VII (ESX), and the poorly characterized "Photorhabdus virulence cassettes (PVC)", PrsW-dependent and MuF phage-capsid-like systems. We present evidence that trafficking of these toxins is often accompanied by autoproteolytic processing catalyzed by HINT, ZU5, PrsW, caspase-like, papain-like, and a novel metallopeptidase associated with the PVC system. We identified over 150 distinct toxin domains in these systems. These span an extraordinary catalytic spectrum to include 23 distinct clades of peptidases, numerous previously unrecognized versions of nucleases and deaminases, ADP-ribosyltransferases, ADP ribosyl cyclases, RelA/SpoT-like nucleotidyltransferases, glycosyltranferases and other enzymes predicted to modify lipids and carbohydrates, and a pore-forming toxin domain. Several of these toxin domains are shared with host-directed effectors of pathogenic bacteria. Over 90 families of immunity proteins might neutralize anywhere between a single to at least 27 distinct types of toxin domains. In some organisms multiple tandem immunity genes or immunity protein domains are organized into polyimmunity loci or polyimmunity proteins. Gene-neighborhood-analysis of polymorphic toxin systems predicts the presence of novel trafficking-related components, and also the organizational logic that allows toxin diversification through recombination. Domain architecture and protein-length analysis revealed that these toxins might be deployed as secreted factors, through directed injection, or via inter-cellular contact facilitated by filamentous structures formed by RHS/YD, filamentous hemagglutinin and other repeats. Phyletic pattern and life-style analysis indicate that polymorphic toxins and polyimmunity loci participate in cooperative behavior and facultative 'cheating' in several ecosystems such as the human oral cavity and soil. Multiple domains from these systems have also been repeatedly transferred to eukaryotes and their viruses, such as the nucleo-cytoplasmic large DNA viruses. CONCLUSIONS Along with a comprehensive inventory of toxins and immunity proteins, we present several testable predictions regarding active sites and catalytic mechanisms of toxins, their processing and trafficking and their role in intra-specific and inter-specific interactions between bacteria. These systems provide insights regarding the emergence of key systems at different points in eukaryotic evolution, such as ADP ribosylation, interaction of myosin VI with cargo proteins, mediation of apoptosis, hyphal heteroincompatibility, hedgehog signaling, arthropod toxins, cell-cell interaction molecules like teneurins and different signaling messengers.
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Affiliation(s)
- Dapeng Zhang
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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14
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Zhang D, Iyer LM, Aravind L. A novel immunity system for bacterial nucleic acid degrading toxins and its recruitment in various eukaryotic and DNA viral systems. Nucleic Acids Res 2011; 39:4532-52. [PMID: 21306995 PMCID: PMC3113570 DOI: 10.1093/nar/gkr036] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The use of nucleases as toxins for defense, offense or addiction of selfish elements is widely encountered across all life forms. Using sensitive sequence profile analysis methods, we characterize a novel superfamily (the SUKH superfamily) that unites a diverse group of proteins including Smi1/Knr4, PGs2, FBXO3, SKIP16, Syd, herpesviral US22, IRS1 and TRS1, and their bacterial homologs. Using contextual analysis we present evidence that the bacterial members of this superfamily are potential immunity proteins for a variety of toxin systems that also include the recently characterized contact-dependent inhibition (CDI) systems of proteobacteria. By analyzing the toxin proteins encoded in the neighborhood of the SUKH superfamily we predict that they possess domains belonging to diverse nuclease and nucleic acid deaminase families. These include at least eight distinct types of DNases belonging to HNH/EndoVII- and restriction endonuclease-fold, and RNases of the EndoU-like and colicin E3-like cytotoxic RNases-folds. The N-terminal domains of these toxins indicate that they are extruded by several distinct secretory mechanisms such as the two-partner system (shared with the CDI systems) in proteobacteria, ESAT-6/WXG-like ATP-dependent secretory systems in Gram-positive bacteria and the conventional Sec-dependent system in several bacterial lineages. The hedgehog-intein domain might also release a subset of toxic nuclease domains through auto-proteolytic action. Unlike classical colicin-like nuclease toxins, the overwhelming majority of toxin systems with the SUKH superfamily is chromosomally encoded and appears to have diversified through a recombination process combining different C-terminal nuclease domains to N-terminal secretion-related domains. Across the bacterial superkingdom these systems might participate in discriminating `self’ or kin from `non-self’ or non-kin strains. Using structural analysis we demonstrate that the SUKH domain possesses a versatile scaffold that can be used to bind a wide range of protein partners. In eukaryotes it appears to have been recruited as an adaptor to regulate modification of proteins by ubiquitination or polyglutamylation. Similarly, another widespread immunity protein from these toxin systems, namely the suppressor of fused (SuFu) superfamily has been recruited for comparable roles in eukaryotes. In animal DNA viruses, such as herpesviruses, poxviruses, iridoviruses and adenoviruses, the ability of the SUKH domain to bind diverse targets has been deployed to counter diverse anti-viral responses by interacting with specific host proteins.
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Affiliation(s)
- Dapeng Zhang
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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15
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Ng CL, Lang K, Meenan NAG, Sharma A, Kelley AC, Kleanthous C, Ramakrishnan V. Structural basis for 16S ribosomal RNA cleavage by the cytotoxic domain of colicin E3. Nat Struct Mol Biol 2010; 17:1241-1246. [PMID: 20852642 PMCID: PMC3755339 DOI: 10.1038/nsmb.1896] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 07/26/2010] [Indexed: 11/08/2022]
Abstract
The toxin colicin E3 targets the 30S subunit of bacterial ribosomes and cleaves a phosphodiester bond in the decoding center. We present the crystal structure of the 70S ribosome in complex with the cytotoxic domain of colicin E3 (E3-rRNase). The structure reveals how the rRNase domain of colicin binds to the A site of the decoding center in the 70S ribosome and cleaves the 16S ribosomal RNA (rRNA) between A1493 and G1494. The cleavage mechanism involves the concerted action of conserved residues Glu62 and His58 of the cytotoxic domain of colicin E3. These residues activate the 16S rRNA for 2' OH-induced hydrolysis. Conformational changes observed for E3-rRNase, 16S rRNA and helix 69 of 23S rRNA suggest that a dynamic binding platform is required for colicin E3 binding and function.
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MESH Headings
- Amino Acid Sequence
- Catalysis
- Colicins/chemistry
- Colicins/metabolism
- Conserved Sequence
- Crystallography, X-Ray
- Escherichia coli/metabolism
- Macromolecular Substances
- Models, Molecular
- Molecular Sequence Data
- Nucleic Acid Conformation
- Protein Conformation
- Protein Structure, Tertiary
- RNA, Messenger/metabolism
- RNA, Ribosomal, 16S/chemistry
- RNA, Ribosomal, 16S/metabolism
- RNA, Ribosomal, 23S/chemistry
- RNA, Ribosomal, 23S/metabolism
- RNA, Transfer, Met/metabolism
- Ribosomes/metabolism
- Sequence Alignment
- Sequence Homology, Amino Acid
- Structure-Activity Relationship
- Thermus thermophilus/metabolism
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Affiliation(s)
- C Leong Ng
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | - Kathrin Lang
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | | | - Amit Sharma
- Department of Biology (Area 10), University of York, York, UK
| | - Ann C Kelley
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
| | | | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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16
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Abstract
Nucleases cleave the phosphodiester bonds of nucleic acids and may be endo or exo, DNase or RNase, topoisomerases, recombinases, ribozymes, or RNA splicing enzymes. In this review, I survey nuclease activities with known structures and catalytic machinery and classify them by reaction mechanism and metal-ion dependence and by their biological function ranging from DNA replication, recombination, repair, RNA maturation, processing, interference, to defense, nutrient regeneration or cell death. Several general principles emerge from this analysis. There is little correlation between catalytic mechanism and biological function. A single catalytic mechanism can be adapted in a variety of reactions and biological pathways. Conversely, a single biological process can often be accomplished by multiple tertiary and quaternary folds and by more than one catalytic mechanism. Two-metal-ion-dependent nucleases comprise the largest number of different tertiary folds and mediate the most diverse set of biological functions. Metal-ion-dependent cleavage is exclusively associated with exonucleases producing mononucleotides and endonucleases that cleave double- or single-stranded substrates in helical and base-stacked conformations. All metal-ion-independent RNases generate 2',3'-cyclic phosphate products, and all metal-ion-independent DNases form phospho-protein intermediates. I also find several previously unnoted relationships between different nucleases and shared catalytic configurations.
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17
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Loll B, Gebhardt M, Wahle E, Meinhart A. Crystal structure of the EndoG/EndoGI complex: mechanism of EndoG inhibition. Nucleic Acids Res 2010; 37:7312-20. [PMID: 19783821 PMCID: PMC2790893 DOI: 10.1093/nar/gkp770] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
EndoG is a ubiquitous nuclease that is translocated into the nucleus during apoptosis to participate in DNA degradation. The enzyme cleaves double- and single-stranded DNA and RNA. Related nucleases are found in eukaryotes and prokaryotes, which have evolved sophisticated mechanisms for genome protection against self-antagonizing nuclease activity. Common mechanisms of inhibition are secretion, sequestration into a separate cellular compartment or by binding to protein inhibitors. Although EndoG is silenced by compartmentalization into the mitochondrial intermembrane space, a nucleus-localized protein inhibitor protects cellular polynucleotides from degradation by stray EndoG under non-apoptotic conditions in Drosophila. Here, we report the first three-dimensional structure of EndoG in complex with its inhibitor EndoGI. Although the mechanism of inhibition is reminiscent of bacterial protein inhibitors, EndoGI has evolved independently from a generic protein-protein interaction module. EndoGI is a two-domain protein that binds the active sites of two monomers of EndoG, with EndoG being sandwiched between EndoGI. Since the amino acid sequences of eukaryotic EndoG homologues are highly conserved, this model is valid for eukaryotic dimeric EndoG in general. The structure indicates that the two active sites of EndoG occupy the most remote spatial position possible at the molecular surface and a concerted substrate processing is unlikely.
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Affiliation(s)
- Bernhard Loll
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany
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18
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Temme C, Weissbach R, Lilie H, Wilson C, Meinhart A, Meyer S, Golbik R, Schierhorn A, Wahle E. The Drosophila melanogaster Gene cg4930 Encodes a High Affinity Inhibitor for Endonuclease G. J Biol Chem 2009; 284:8337-48. [PMID: 19129189 DOI: 10.1074/jbc.m808319200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endonuclease G (EndoG) is a mitochondrial enzyme believed to be released during apoptosis to participate in the degradation of nuclear DNA. This paper describes a Drosophila protein, EndoGI, which inhibits EndoG specifically. EndoG and EndoGI associate with subpicomolar affinity, forming a 2:1 complex in which dimeric EndoG is bound by two tandemly repeated homologous domains of monomeric EndoGI. Binding appears to involve the active site of EndoG. EndoGI is present in the cell nucleus at micromolar concentrations. Upon induction of apoptosis, levels of the inhibitor appear to be reduced, and it is relocalized to the cytoplasm. EndoGI, encoded by the predicted open reading frame cg4930, is expressed throughout Drosophila development. Flies homozygous for a hypomorphic EndoGI mutation have a strongly reduced viability, which is modulated by genetic background and diet. We propose that EndoGI protects the cell against low levels of EndoG outside mitochondria.
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Affiliation(s)
- Claudia Temme
- Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 3, 06120 Halle, Germany
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19
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Lancaster LE, Savelsbergh A, Kleanthous C, Wintermeyer W, Rodnina MV. Colicin E3 cleavage of 16S rRNA impairs decoding and accelerates tRNA translocation on Escherichia coli ribosomes. Mol Microbiol 2008; 69:390-401. [PMID: 18485067 PMCID: PMC2615495 DOI: 10.1111/j.1365-2958.2008.06283.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cytotoxin colicin E3 targets the 30S subunit of bacterial ribosomes and specifically cleaves 16S rRNA at the decoding centre, thereby inhibiting translation. Although the cleavage site is well known, it is not clear which step of translation is inhibited. We studied the effects of colicin E3 cleavage on ribosome functions by analysing individual steps of protein synthesis. We find that the cleavage affects predominantly the elongation step. The inhibitory effect of colicin E3 cleavage originates from the accumulation of sequential impaired decoding events, each of which results in low occupancy of the A site and, consequently, decreasing yield of elongating peptide. The accumulation leads to an almost complete halt of translation after reading of a few codons. The cleavage of 16S rRNA does not impair monitoring of codon-anticodon complexes or GTPase activation during elongation-factor Tu-dependent binding of aminoacyl-tRNA, but decreases the stability of the codon-recognition complex and slows down aminoacyl-tRNA accommodation in the A site. The tRNA-mRNA translocation is faster on colicin E3-cleaved than on intact ribosomes and is less sensitive to inhibition by the antibiotic viomycin.
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Affiliation(s)
- Lorna E Lancaster
- Institute of Molecular Biology, University of Witten/Herdecke, 58448 Witten, Germany
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20
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Goyal K, Mande SC. Exploiting 3D structural templates for detection of metal-binding sites in protein structures. Proteins 2008; 70:1206-18. [PMID: 17847089 DOI: 10.1002/prot.21601] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
High throughput structural genomics efforts have been making the structures of proteins available even before their function has been fully characterized. Therefore, methods that exploit the structural knowledge to provide evidence about the functions of proteins would be useful. Such methods would be needed to complement the sequence-based function annotation approaches. The current study describes generation of 3D-structural motifs for metal-binding sites from the known metalloproteins. It then scans all the available protein structures in the PDB database for putative metal-binding sites. Our analysis predicted more than 1000 novel metal-binding sites in proteins using three-residue templates, and more than 150 novel metal-binding sites using four-residue templates. Prediction of metal-binding site in a yeast protein YDR533c led to the hypothesis that it might function as metal-dependent amidopeptidase. The structural motifs identified by our method present novel metal-binding sites that reveal newer mechanisms for a few well-known proteins.
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Affiliation(s)
- Kshama Goyal
- Laboratory of Structural Biology, Center for DNA Fingerprinting and Diagnostics, Nacharam, Hyderabad 500076, Andhra Pradesh, India
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21
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Cascales E, Buchanan SK, Duché D, Kleanthous C, Lloubès R, Postle K, Riley M, Slatin S, Cavard D. Colicin biology. Microbiol Mol Biol Rev 2007; 71:158-229. [PMID: 17347522 PMCID: PMC1847374 DOI: 10.1128/mmbr.00036-06] [Citation(s) in RCA: 784] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS regulation; their release into the extracellular medium, which involves the colicin lysis protein; and their uptake mechanisms and modes of action. Colicins are organized into three domains, each one involved in a different step of the process of killing sensitive bacteria. The structures of some colicins are known at the atomic level and are discussed. Colicins exert their lethal action by first binding to specific receptors, which are outer membrane proteins used for the entry of specific nutrients. They are then translocated through the outer membrane and transit through the periplasm by either the Tol or the TonB system. The components of each system are known, and their implication in the functioning of the system is described. Colicins then reach their lethal target and act either by forming a voltage-dependent channel into the inner membrane or by using their endonuclease activity on DNA, rRNA, or tRNA. The mechanisms of inhibition by specific and cognate immunity proteins are presented. Finally, the use of colicins as laboratory or biotechnological tools and their mode of evolution are discussed.
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Affiliation(s)
- Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires,Institut de Biologie Structurale et Microbiologie, Centre National de la Recherche Scientifique, UPR 9027, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
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22
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Yajima S, Inoue S, Ogawa T, Nonaka T, Ohsawa K, Masaki H. Structural basis for sequence-dependent recognition of colicin E5 tRNase by mimicking the mRNA-tRNA interaction. Nucleic Acids Res 2006; 34:6074-82. [PMID: 17099236 PMCID: PMC1669751 DOI: 10.1093/nar/gkl729] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Colicin E5—a tRNase toxin—specifically cleaves QUN (Q: queuosine) anticodons of the Escherichia coli tRNAs for Tyr, His, Asn and Asp. Here, we report the crystal structure of the C-terminal ribonuclease domain (CRD) of E5 complexed with a substrate analog, namely, dGpdUp, at a resolution of 1.9 Å. Thisstructure is the first to reveal the substrate recognition mechanism of sequence-specific ribonucleases. E5-CRD realized the strict recognition for both the guanine and uracil bases of dGpdUp forming Watson–Crick-type hydrogen bonds and ring stacking interactions, thus mimicking the codons of mRNAs to bind to tRNA anticodons. The docking model of E5-CRD with tRNA also suggests its substrate preference for tRNA over ssRNA. In addition, the structure of E5-CRD/dGpdUp along with the mutational analysis suggests that Arg33 may play an important role in the catalytic activity, and Lys25/Lys60 may also be involved without His in E5-CRD. Finally, the comparison of the structures of E5-CRD/dGpdUp and E5-CRD/ImmE5 (an inhibitor protein) complexes suggests that the binding mode of E5-CRD and ImmE5 mimics that of mRNA and tRNA; this may represent the evolutionary pathway of these proteins from the RNA–RNA interaction through the RNA–protein interaction of tRNA/E5-CRD.
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Affiliation(s)
- Shunsuke Yajima
- Department of Bioscience, Tokyo University of Agriculture, Sakuragaoka 1-1-1, Setagaya-ku, Tokyo 156-8502, Japan.
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23
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Luna-Chávez C, Lin YL, Huang RH. Molecular Basis of Inhibition of the Ribonuclease Activity in Colicin E5 by Its Cognate Immunity Protein. J Mol Biol 2006; 358:571-9. [PMID: 16524591 DOI: 10.1016/j.jmb.2006.02.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Revised: 01/31/2006] [Accepted: 02/06/2006] [Indexed: 10/25/2022]
Abstract
Colicin E5 is a tRNA-specific ribonuclease that recognizes and cleaves four tRNAs in Escherichia coli that contain the hypermodified nucleoside queuosine (Q) at the wobble position. Cells that produce colicin E5 also synthesize the cognate immunity protein (Im5) that rapidly and tightly associates with colicin E5 to prevent it from cleaving its own tRNAs to avoid suicide. We report here the crystal structure of Im5 in a complex with the activity domain of colicin E5 (E5-CRD) at 1.15A resolution. The structure reveals an extruded domain from Im5 that docks into the recessed RNA binding cleft in E5-CRD, resulting in extensive interactions between the two proteins. The interactions are primarily hydrophilic, with an interface that contains complementary surface charges between the two proteins. Detailed interactions in three separate regions of the interface account for specific recognition of colicin E5 by Im5. Furthermore, single-site mutational studies of Im5 confirmed the important role of particular residues in recognition and binding of colicin E5. Structural comparison of the complex reported here with E5-CRD alone, as well as with a docking model of RNA-E5-CRD, indicates that Im5 achieves its inhibition by physically blocking the cleft in colicin E5 that engages the RNA substrate.
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Affiliation(s)
- César Luna-Chávez
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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24
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Mosbahi K, Walker D, James R, Moore GR, Kleanthous C. Global structural rearrangement of the cell penetrating ribonuclease colicin E3 on interaction with phospholipid membranes. Protein Sci 2006; 15:620-7. [PMID: 16452623 PMCID: PMC2249781 DOI: 10.1110/ps.051890306] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Nuclease type colicins and related bacteriocins possess the unprecedented ability to translocate an enzymatic polypeptide chain across the Gram-negative cell envelope. Here we use the rRNase domain of the cytotoxic ribonuclease colicin E3 to examine the structural changes on its interaction with the membrane. Using phospholipid vesicles as model membranes we show that anionic membranes destabilize the nuclease domain of the rRNase type colicin E3. Intrinsic tryptophan fluorescence and circular dichroism show that vesicles consisting of pure DOPA act as a powerful protein denaturant toward the rRNase domain, although this interaction can be entirely prevented by the addition of salt. Binding of E3 rRNase to DOPA vesicles is an endothermic process (DeltaH=24 kcal mol-1), reflecting unfolding of the protein. Consistent with this, binding of a highly destabilized mutant of the E3 rRNase to DOPA vesicles is exothermic. With mixed vesicles containing anionic and neutral phospholipids at a ratio of 1:3, set to mimic the charge of the Escherichia coli inner membrane, destabilization of E3 rRNase is lessened, although the melting temperature of the protein at pH 7.0 is greatly reduced from 50 degrees C to 30 degrees C. The interaction of E3 rRNase with 1:3 DOPA:DOPC vesicles is also highly dependent on both ionic strength and temperature. We discuss these results in terms of the likely interaction of the E3 rRNase and the related E9 DNase domains with the E. coli inner membrane and their subsequent translocation to the cell cytoplasm.
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25
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Yajima S, Nakanishi K, Takahashi K, Ogawa T, Hidaka M, Kezuka Y, Nonaka T, Ohsawa K, Masaki H. Relation between tRNase activity and the structure of colicin D according to X-ray crystallography. Biochem Biophys Res Commun 2004; 322:966-73. [PMID: 15336558 DOI: 10.1016/j.bbrc.2004.07.206] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2004] [Indexed: 11/30/2022]
Abstract
Colicin D is a plasmid-encoded proteinaceous toxin which kills sensitive Escherichia coli. Toxicity stems from ribonuclease activity that targets exclusively four isoacceptors of tRNA(Arg) with a cleavage position between 38 and 39 of the corresponding anticodons. Since no other tRNAs with the same sequences at 38 and 39 as tRNA(Arg)s are cleaved, colicin D should be capable of recognizing some higher order structure of tRNAs. We report here two crystal structures of catalytic domains of colicin D which have different N-terminal lengths, both complexed with its cognate inhibitor protein, ImmD. A row of positive charge patches is found on the surface of the catalytic domain, suggestive of the binding site of the tRNAs. This finding, together with our refined tRNase activity experiments, indicates that the catalytic domain starting at position 595 has activity almost equivalent to that of colicin D.
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Affiliation(s)
- Shunsuke Yajima
- Department of Bioscience, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan.
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26
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Zhou HX. Association and dissociation kinetics of colicin E3 and immunity protein 3: convergence of theory and experiment. Protein Sci 2004; 12:2379-82. [PMID: 14500897 PMCID: PMC2366933 DOI: 10.1110/ps.03216203] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The rapid binding of cytotoxic colicin E3 by its cognate immunity protein Im3 is essential in safeguarding the producing cell. The X-ray structure of the E3/Im3 complex shows that the Im3 molecule interfaces with both the C-terminal ribonuclease (RNase) domain and the N-terminal translocation domain of E3. The association and dissociation rates of the RNase domain and Im3 show drastically different sensitivities to ionic strength, as previously rationalized for electrostatically enhanced diffusion-limited protein-protein associations. Relative to binding to the RNase domain, binding to full-length E3 shows a comparable association rate but a significantly lower dissociation rate. This outcome is just what was anticipated by a theory for the binding of two linked domains to a protein. The E3/Im3 system thus provides a powerful paradigm for the interplay of theory and experiment.
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Affiliation(s)
- Huan-Xiang Zhou
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306, USA.
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27
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Walker D, Lancaster L, James R, Kleanthous C. Identification of the catalytic motif of the microbial ribosome inactivating cytotoxin colicin E3. Protein Sci 2004; 13:1603-11. [PMID: 15133158 PMCID: PMC2279995 DOI: 10.1110/ps.04658504] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Colicin E3 is a cytotoxic ribonuclease that specifically cleaves 16S rRNA at the ribosomal A-site to abolish protein synthesis in sensitive Escherichia coli cells. We have performed extensive mutagenesis of the 96-residue colicin E3 cytotoxic domain (E3 rRNase), assayed mutant colicins for in vivo cytotoxicity, and tested the corresponding E3 rRNase domains for their ability to inactivate ribosome function in vitro. From 21 alanine mutants, we identified five positions where mutation resulted in a colicin with no measurable cytotoxicity (Y52, D55, H58, E62, and Y64) and four positions (R40, R42, E60, and R90) where mutation caused a significant reduction in cytotoxicity. Mutations that were found to have large in vivo and in vitro effects were tested for structural integrity through circular dichroism and fluorescence spectroscopy using purified rRNase domains. Our data indicate that H58 and E62 likely act as the acid-base pair during catalysis with other residues likely involved in transition state stabilization. Both the Y52 and Y64 mutants were found to be highly destabilized and this is the likely origin of the loss of their cytotoxicity. The identification of important active site residues and sequence alignments of known rRNase homologs has allowed us to identify other proteins containing the putative rRNase active site motif. Proteins that contained this active site motif included three hemagglutinin-type adhesins and we speculate that these have evolved to deliver a cytotoxic rRNase into eukaryotic cells during pathogenesis.
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Affiliation(s)
- Daniel Walker
- Department of Biology, University of York, York YO10 5YW, UK
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28
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Graille M, Mora L, Buckingham RH, van Tilbeurgh H, de Zamaroczy M. Structural inhibition of the colicin D tRNase by the tRNA-mimicking immunity protein. EMBO J 2004; 23:1474-82. [PMID: 15014439 PMCID: PMC391069 DOI: 10.1038/sj.emboj.7600162] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 02/13/2004] [Indexed: 11/09/2022] Open
Abstract
Colicins are toxins secreted by Escherichia coli in order to kill their competitors. Colicin D is a 75 kDa protein that consists of a translocation domain, a receptor-binding domain and a cytotoxic domain, which specifically cleaves the anticodon loop of all four tRNA(Arg) isoacceptors, thereby inactivating protein synthesis and leading to cell death. Here we report the 2.0 A resolution crystal structure of the complex between the toxic domain and its immunity protein ImmD. Neither component shows structural homology to known RNases or their inhibitors. In contrast to other characterized colicin nuclease-Imm complexes, the colicin D active site pocket is completely blocked by ImmD, which, by bringing a negatively charged cluster in opposition to a positively charged cluster on the surface of colicin D, appears to mimic the tRNA substrate backbone. Site-directed mutations affecting either the catalytic domain or the ImmD protein have led to the identification of the residues vital for catalytic activity and for the tight colicin D/ImmD interaction that inhibits colicin D toxicity and tRNase catalytic activity.
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Affiliation(s)
| | | | | | - Herman van Tilbeurgh
- LEBS, CNRS, UPR 9063, Gif sur Yvette, France
- IBBMC, CNRS, UMR 8619, Université Paris 11, Orsay, France
| | - Miklos de Zamaroczy
- IBPC, CNRS, UPR 9073, Paris, France
- IBPC, CNRS, UPR 9073, 13 rue Pierre et Marie Curie, 75005 Paris, France. Tel.: +33 1 5841 51 54; Fax: +33 1 5841 50 20; E-mail:
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29
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Ben-Zeev E, Zarivach R, Shoham M, Yonath A, Eisenstein M. Prediction of the structure of the complex between the 30S ribosomal subunit and colicin E3 via weighted-geometric docking. J Biomol Struct Dyn 2003; 20:669-76. [PMID: 12643769 DOI: 10.1080/07391102.2003.10506883] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Colicin E3 kills Escherichia coli cells by ribonucleolytic cleavage in the 16S rRNA. The cleavage occurs at the ribosomal decoding A-site between nucleotides A1493 and G1494. The breaking of this single phosphodiester bond results in a complete termination of protein biosynthesis leading to cell death. A model structure of the complex of the ribosomal subunit 30S and colicin E3 was constructed by means of a new weighted-geometric docking algorithm, in which interactions involving specified parts of the molecular surface can be up-weighted, allowing incorporation of experimental data in the docking search. Our model, together with available experimental data, predicts the role of the catalytic residues of colicin E3. In addition, it suggests that bound acidic immunity protein inhibits the enzymatic activity of colicin E3 by electrostatic repulsion of the negatively charged substrate.
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Affiliation(s)
- Efrat Ben-Zeev
- Weizmann Institute of Science, Department of Biological Chemistry, Rehovot, 76100 Israel
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30
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de Zamaroczy M, Buckingham RH. Importation of nuclease colicins into E coli cells: endoproteolytic cleavage and its prevention by the immunity protein. Biochimie 2002; 84:423-32. [PMID: 12423785 DOI: 10.1016/s0300-9084(02)01426-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A major group of colicins comprises molecules that possess nuclease activity and kill sensitive cells by cleaving RNA or DNA. Recent data open the possibility that the tRNase colicin D, the rRNase colicin E3 and the DNase colicin E7 undergo proteolytic processing, such that only the C-terminal domain of the molecule, carrying the nuclease activity, enters the cytoplasm. The proteases responsible for the proteolytic processing remain unidentified. In the case of colicin D, the characterization of a colicin D-resistant mutant shows that the inner membrane protease LepB is involved in colicin D toxicity, but is not solely responsible for the cleavage of colicin D. The lepB mutant resistant to colicin D remains sensitive to other colicins tested (B, E1, E3 and E2), and the mutant protease retains activity towards its normal substrates. The cleavage of colicin D observed in vitro releases a C-terminal fragment retaining tRNase activity, and occurs in a region of the amino acid sequence that is conserved in other nuclease colicins, suggesting that they may also require a processing step for their cytotoxicity. The immunity proteins of both colicins D and E3 appear to have a dual role, protecting the colicin molecule against proteolytic cleavage and inhibiting the nuclease activity of the colicin. The possibility that processing is an essential step common to cell killing by all nuclease colicins, and that the immunity protein must be removed from the colicin prior to processing, is discussed.
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Affiliation(s)
- Miklos de Zamaroczy
- Institut de Biologie Physico-Chimique, CNRS, UPR 9073, 13, rue Pierre et Marie Curie 75005, Paris, France.
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31
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Abstract
To kill Escherichia coli, toxic proteins, called colicins, pass through the permeability barrier created by the outer membrane (OM) of the bacterial cell envelope. We consider a variety of different colicins, including A, B, D, E1, E3, Ia, M and N, that penetrate through the porins OmpF, FepA, BtuB, Cir and FhuA, to subsequently interact with a few targets in the periplasm, including TolA, TolB, TolC and TonB. We review the mechanisms, demonstrated and postulated, by which such toxins enter bacterial cells, from the initial binding stage on the cell surface to the internalization reaction through the OM bilayer. Our discussions endeavor to answer two main questions: what is the origin of colicin-binding affinity and specificity, and after adsorption to OM porins, do colicin polypeptides translocate through porin channels, or enter by another, currently unknown pathway?
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Affiliation(s)
- Zhenghua Cao
- Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Norman, OK 73019, USA
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32
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Abstract
Colicins E5 and D cleave the anticodon loops of distinct tRNAs of Escherichia coli both in vivo and in vitro, which accounts for their bactericidal actions through depletion of tRNAs and prevention of protein synthesis. The targets of colicin E5 are five tRNA species for four amino acids, tyrosine, histidine, asparagine and aspartic acid, and those of colicin D are four isoaccepting tRNAs for arginine. These two colicins represent a new class, the "tRNase-type", of the nuclease-type colicins, which previously comprised the DNase-type and ribotoxin-type (or rRNase-type). On the other hand, a certain clinical E. coli strain produces a potentially suicidal "anticodon-nuclease", PrrC, in response to phage T4 infection, which specifically cleaves its own lysine tRNA. For these three tRNases, i.e. colicins E5 and D, and PrrC, the substrates and reaction products, as well as their physiological consequences, are very similar to each other, but so many molecular features are different that these three proteins are assumed to have acquired similar functions through evolutionary convergence from different origins.
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Affiliation(s)
- Haruhiko Masaki
- Department of Biotechnology, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
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33
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Kolade OO, Carr SB, Kühlmann UC, Pommer A, Kleanthous C, Bouchcinsky CA, Hemmings AM. Structural aspects of the inhibition of DNase and rRNase colicins by their immunity proteins. Biochimie 2002; 84:439-46. [PMID: 12423787 DOI: 10.1016/s0300-9084(02)01451-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Nuclease E colicins that exert their cytotoxic activity through either non-specific DNase or specific rRNase action are inhibited by immunity proteins in a high affinity interaction that gives complete protection to the producing host cell from the deleterious effects of the toxin. Previous X-ray crystallographic analysis of these systems has revealed that in both cases, the immunity protein inhibitor forms its highly stable complex with the enzyme by binding as an exosite inhibitor-adjacent to, but not obscuring, the enzyme active site. The structures of the free E9 DNase domain and its complex with an ssDNA substrate now show that inhibition is achieved without deformation of the enzyme and by occlusion of a limited number of residues of the enzyme critical in recognition and binding of the substrate that are 3' to the cleaved scissile phosphodiester. No sequence or structural similarity is evident between the two classes of cytotoxic domain, and the heterodimer interfaces are also dissimilar. Thus, whilst these structures suggest the basis for specificity in each case, they give few indications as to the basis for the remarkably strong binding that is observed. Structural analyses of complexes bearing single site mutations in the immunity protein at the heterodimer interface reveal further differences. For the DNases, a largely plastic interface is suggested, where optimal binding may be achieved in part by rigid body adjustment in the relative positions of inhibitor and enzyme. For the rRNases, a large solvent-filled cavity is found at the immunity-enzyme interface, suggesting that other considerations, such as that arising from the entropy contribution from bound water molecules, may have greater significance in the determination of rRNase complex affinity than for the DNases.
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Affiliation(s)
- Olatomirin O Kolade
- Schools of Biological and Chemical Sciences, University of East Anglia, Norwich, NR4 7TJ, Norfolk, UK
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34
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Abstract
The process by which the endonuclease domain of colicin E9 is translocated across the outer membrane, the periplasmic space and the cytoplasmic membrane to reach the cytoplasm of E. coli cells, resulting in DNA degradation and cell death, is a unique event in prokaryotic biology. Although considerable information is known about the role of the BtuB outer membrane receptor, as well as the mostly periplasmic Tol proteins that are essential for the translocation process, the precise nature of the interactions between colicin E9 and these proteins remains to be elucidated. In this review, we consider our current understanding of the key events in this process, concentrating on recent findings concerning receptor-binding, translocation and the mechanism of cytotoxicity.
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Affiliation(s)
- Richard James
- Division of microbiology and infectious diseases, University Hospital, University of Nottingham, NG7 2UH, Nottingham, UK.
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35
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Zarivach R, Ben-Zeev E, Wu N, Auerbach T, Bashan A, Jakes K, Dickman K, Kosmidis A, Schluenzen F, Yonath A, Eisenstein M, Shoham M. On the interaction of colicin E3 with the ribosome. Biochimie 2002; 84:447-54. [PMID: 12423788 DOI: 10.1016/s0300-9084(02)01449-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Colicin E3 is a protein that kills Escherichia coli cells by a process that involves binding to a surface receptor, entering the cell and inactivating its protein biosynthetic machinery. Colicin E3 kills cells by a catalytic mechanism of a specific ribonucleolytic cleavage in 16S rRNA at the ribosomal decoding A-site between A1493 and G1494 (E. coli numbering system). The breaking of this single phosphodiester bond results in a complete cessation of protein biosynthesis and cell death. The inactive E517Q mutant of the catalytic domain of colicin E3 binds to 30S ribosomal subunits of Thermus thermophilus, as demonstrated by an immunoblotting assay. A model structure of the complex of the ribosomal subunit 30S and colicin E3, obtained via docking, explains the role of the catalytic residues, suggests a catalytic mechanism and provides insight into the specificity of the reaction. Furthermore, the model structure suggests that the inhibitory action of bound immunity is due to charge repulsion of this acidic protein by the negatively charged rRNA backbone
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Affiliation(s)
- Raz Zarivach
- Weizmann Institute of Science, Department of Structural Biology, Rehovot 76100, Israel
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36
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Soelaiman S, Jakes K, Wu N, Li C, Shoham M. Crystal structure of colicin E3: implications for cell entry and ribosome inactivation. Mol Cell 2001; 8:1053-62. [PMID: 11741540 DOI: 10.1016/s1097-2765(01)00396-3] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Colicins kill E. coli by a process that involves binding to a surface receptor, entering the cell, and, finally, intoxicating it. The lethal action of colicin E3 is a specific cleavage in the ribosomal decoding A site. The crystal structure of colicin E3, reported here in a binary complex with its immunity protein (IP), reveals a Y-shaped molecule with the receptor binding domain forming a 100 A long stalk and the two globular heads of the translocation domain (T) and the catalytic domain (C) comprising the two arms. Active site residues are D510, H513, E517, and R545. IP is buried between T and C. Rather than blocking the active site, IP prevents access of the active site to the ribosome.
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Affiliation(s)
- S Soelaiman
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
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37
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Abstract
Immunity proteins are high affinity inhibitors of colicins--SOS-induced toxins released by bacteria during times of stress. Recent work has shown that nuclease-specific immunity proteins are exosite inhibitors, binding adjacent to the enzyme active site and inhibiting colicin activity indirectly. Unusually, their binding sites comprise a near contiguous sequence that lies N-terminal to active site sequences, raising the possibility that immunity proteins bind colicins co-translationally. Exosite binding accounts for the extensive sequence diversity seen at the interfaces of colicin-immunity protein complexes, which is not only a selective advantage to colicin-producing bacteria, but also represents a powerful model system for studying specificity in protein-protein recognition.
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Affiliation(s)
- C Kleanthous
- School of Biological Sciences, University of East Anglia, Norwich, UK NR4 7TJ.
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