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Gallot-Lavallée L, Jerlström-Hultqvist J, Zegarra-Vidarte P, Salas-Leiva DE, Stairs CW, Čepička I, Roger AJ, Archibald JM. Massive intein content in Anaeramoeba reveals aspects of intein mobility in eukaryotes. Proc Natl Acad Sci U S A 2023; 120:e2306381120. [PMID: 38019867 PMCID: PMC10710043 DOI: 10.1073/pnas.2306381120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Inteins are self-splicing protein elements found in viruses and all three domains of life. How the DNA encoding these selfish elements spreads within and between genomes is poorly understood, particularly in eukaryotes where inteins are scarce. Here, we show that the nuclear genomes of three strains of Anaeramoeba encode between 45 and 103 inteins, in stark contrast to four found in the most intein-rich eukaryotic genome described previously. The Anaeramoeba inteins reside in a wide range of proteins, only some of which correspond to intein-containing proteins in other eukaryotes, prokaryotes, and viruses. Our data also suggest that viruses have contributed to the spread of inteins in Anaeramoeba and the colonization of new alleles. The persistence of Anaeramoeba inteins might be partly explained by intragenomic movement of intein-encoding regions from gene to gene. Our intein dataset greatly expands the spectrum of intein-containing proteins and provides insights into the evolution of inteins in eukaryotes.
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Affiliation(s)
- Lucie Gallot-Lavallée
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
- Institute for Comparative Genomics, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
| | - Jon Jerlström-Hultqvist
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
- Institute for Comparative Genomics, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
- Microbiology and Immunology, Department of Cell and Molecular Biology, Biomedical Centre, Uppsala University, Uppsala751 24, Sweden
| | - Paula Zegarra-Vidarte
- Microbiology and Immunology, Department of Cell and Molecular Biology, Biomedical Centre, Uppsala University, Uppsala751 24, Sweden
| | - Dayana E. Salas-Leiva
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
- Institute for Comparative Genomics, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
| | - Courtney W. Stairs
- Microbiology Group, Department of Biology, Lund University, Lund223 62, Sweden
| | - Ivan Čepička
- Department of Zoology, Charles University, Prague128 00, Czech Republic
| | - Andrew J. Roger
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
- Institute for Comparative Genomics, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
| | - John M. Archibald
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
- Institute for Comparative Genomics, Dalhousie University, Halifax, Nova ScotiaB3H 4R2, Canada
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2
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SufB intein splicing in Mycobacterium tuberculosis is influenced by two remote conserved N-extein histidines. Biosci Rep 2022; 42:230724. [PMID: 35234249 PMCID: PMC8891592 DOI: 10.1042/bsr20212207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 01/11/2022] [Accepted: 01/27/2022] [Indexed: 11/24/2022] Open
Abstract
Inteins are auto-processing domains that implement a multistep biochemical reaction termed protein splicing, marked by cleavage and formation of peptide bonds. They excise from a precursor protein, generating a functional protein via covalent bonding of flanking exteins. We report the kinetic study of splicing and cleavage reaction in [Fe–S] cluster assembly protein SufB from Mycobacterium tuberculosis (Mtu). Although it follows a canonical intein splicing pathway, distinct features are added by extein residues present in the active site. Sequence analysis identified two conserved histidines in the N-extein region; His-5 and His-38. Kinetic analyses of His-5Ala and His-38Ala SufB mutants exhibited significant reductions in splicing and cleavage rates relative to the SufB wildtype (WT) precursor protein. Structural analysis and molecular dynamics (MD) simulations suggested that Mtu SufB displays a unique mechanism where two remote histidines work concurrently to facilitate N-terminal cleavage reaction. His-38 is stabilized by the solvent-exposed His-5, and can impact N–S acyl shift by direct interaction with the catalytic Cys1. Development of inteins as biotechnological tools or as pathogen-specific novel antimicrobial targets requires a more complete understanding of such unexpected roles of conserved extein residues in protein splicing.
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3
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Yalala VR, Lynch AK, Mills KV. Conditional Alternative Protein Splicing Promoted by Inteins from Haloquadratum walsbyi. Biochemistry 2022; 61:294-302. [PMID: 35073064 PMCID: PMC8847336 DOI: 10.1021/acs.biochem.1c00788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein splicing is a post-translational process by which an intervening protein, or an intein, catalyzes its own excision from flanking polypeptides, or exteins, coupled to extein ligation. Four inteins interrupt the MCM helicase of the halophile Haloquadratum walsbyi, two of which are mini-inteins that lack a homing endonuclease. Both inteins can be overexpressed in Escherichia coli and purified as unspliced precursors; splicing can be induced in vitro by incubation with salt. However, one intein can splice in 0.5 M NaCl in vitro, whereas the other splices efficiently only in buffer containing over 2 M NaCl; the organism also requires high salt to grow, with the standard growth media containing over 3 M NaCl and about 0.75 M magnesium salts. Consistent with this difference in salt-dependent activity, an intein-containing precursor protein with both inteins promotes conditional alternative protein splicing (CAPS) to yield different spliced products dependent on the salt concentration. Native Trp fluorescence of the inteins suggests that the difference in activity may be due to partial unfolding of the inteins at lower salt concentrations. This differential salt sensitivity of intein activity may provide a useful mechanism for halophiles to respond to environmental changes.
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Affiliation(s)
- Vaishnavi R Yalala
- Department of Chemistry, College of the Holy Cross, 1 College Street, Worcester, Massachusetts 01610, United States
| | - Abigeal K Lynch
- Department of Chemistry, College of the Holy Cross, 1 College Street, Worcester, Massachusetts 01610, United States
| | - Kenneth V Mills
- Department of Chemistry, College of the Holy Cross, 1 College Street, Worcester, Massachusetts 01610, United States
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4
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Tharappel AM, Li Z, Li H. Inteins as Drug Targets and Therapeutic Tools. Front Mol Biosci 2022; 9:821146. [PMID: 35211511 PMCID: PMC8861304 DOI: 10.3389/fmolb.2022.821146] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/10/2022] [Indexed: 12/12/2022] Open
Abstract
Multidrug-resistant pathogens are of significant concern in recent years. Hence new antifungal and anti-bacterial drug targets are urgently needed before the situation goes beyond control. Inteins are polypeptides that self-splice from exteins without the need for cofactors or external energy, resulting in joining of extein fragments. Inteins are present in many organisms, including human pathogens such as Mycobacterium tuberculosis, Cryptococcus neoformans, C. gattii, and Aspergillus fumigatus. Because intein elements are not present in human genes, they are attractive drug targets to develop antifungals and antibiotics. Thus far, a few inhibitors of intein splicing have been reported. Metal-ions such as Zn2+ and Cu2+, and platinum-containing compound cisplatin inhibit intein splicing in M. tuberculosis and C. neoformans by binding to the active site cysteines. A small-molecule inhibitor 6G-318S and its derivative 6G-319S are found to inhibit intein splicing in C. neoformans and C. gattii with a MIC in nanomolar concentrations. Inteins have also been used in many other applications. Intein can be used in activating a protein inside a cell using small molecules. Moreover, split intein can be used to deliver large genes in experimental gene therapy and to kill selected species in a mixed population of microbes by taking advantage of the toxin-antitoxin system. Furthermore, split inteins are used in synthesizing cyclic peptides and in developing cell culture model to study infectious viruses including SARS-CoV-2 in the biosafety level (BSL) 2 facility. This mini-review discusses the recent research developments of inteins in drug discovery and therapeutic research.
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Affiliation(s)
- Anil Mathew Tharappel
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Zhong Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Hongmin Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
- BIO5 Institute, The University of Arizona, Tucson, AZ, United States
- *Correspondence: Hongmin Li,
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Panda S, Nanda A, Nasker SS, Sen D, Mehra A, Nayak S. Metal effect on intein splicing: A review. Biochimie 2021; 185:53-67. [PMID: 33727137 DOI: 10.1016/j.biochi.2021.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 03/04/2021] [Accepted: 03/06/2021] [Indexed: 02/08/2023]
Abstract
Inteins are intervening polypeptides that interrupt the functional domains of several important proteins across the three domains of life. Inteins excise themselves from the precursor protein, ligating concomitant extein residues in a process called protein splicing. Post-translational auto-removal of inteins remain critical for the generation of active proteins. The perspective of inteins in science is a robust field of research, however fundamental studies centralized upon splicing regulatory mechanism are imperative for addressing more intricate issues. Controlled engineering of intein splicing has many applications; intein inhibition can facilitate novel drug design, while activation of intein splicing is exploited in protein purification. This paper provides a comprehensive review of the past and recent advances in the splicing regulation via metal-intein interaction. We compare the behavior of different metal ions on diverse intein systems. Though metals such as Zn, Cu, Pt, Cd, Co, Ni exhibit intein inhibitory effect heterogeneously on different inteins, divalent metal ions such as Ca and Mg fail to do so. The observed diversity in the metal-intein interaction arises mostly due to intein polymorphism and variations in atomic structure of metals. A mechanistic understanding of intein regulation by metals in native as well as synthetically engineered intein systems may yield potent intein inhibitors via direct or indirect approach.
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Affiliation(s)
- Sunita Panda
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Ananya Nanda
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Sourya Subhra Nasker
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Debjani Sen
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Ashwaria Mehra
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Sasmita Nayak
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India.
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6
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Inteins in Science: Evolution to Application. Microorganisms 2020; 8:microorganisms8122004. [PMID: 33339089 PMCID: PMC7765530 DOI: 10.3390/microorganisms8122004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 12/09/2020] [Accepted: 12/09/2020] [Indexed: 12/20/2022] Open
Abstract
Inteins are mobile genetic elements that apply standard enzymatic strategies to excise themselves post-translationally from the precursor protein via protein splicing. Since their discovery in the 1990s, recent advances in intein technology allow for them to be implemented as a modern biotechnological contrivance. Radical improvement in the structure and catalytic framework of cis- and trans-splicing inteins devised the development of engineered inteins that contribute to various efficient downstream techniques. Previous literature indicates that implementation of intein-mediated splicing has been extended to in vivo systems. Besides, the homing endonuclease domain also acts as a versatile biotechnological tool involving genetic manipulation and control of monogenic diseases. This review orients the understanding of inteins by sequentially studying the distribution and evolution pattern of intein, thereby highlighting a role in genetic mobility. Further, we include an in-depth summary of specific applications branching from protein purification using self-cleaving tags to protein modification, post-translational processing and labelling, followed by the development of intein-based biosensors. These engineered inteins offer a disruptive approach towards research avenues like biomaterial construction, metabolic engineering and synthetic biology. Therefore, this linear perspective allows for a more comprehensive understanding of intein function and its diverse applications.
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Beyer HM, Virtanen SI, Aranko AS, Mikula KM, Lountos GT, Wlodawer A, Ollila OHS, Iwaï H. The Convergence of the Hedgehog/Intein Fold in Different Protein Splicing Mechanisms. Int J Mol Sci 2020; 21:ijms21218367. [PMID: 33171880 PMCID: PMC7664689 DOI: 10.3390/ijms21218367] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/01/2020] [Accepted: 11/05/2020] [Indexed: 11/16/2022] Open
Abstract
Protein splicing catalyzed by inteins utilizes many different combinations of amino-acid types at active sites. Inteins have been classified into three classes based on their characteristic sequences. We investigated the structural basis of the protein splicing mechanism of class 3 inteins by determining crystal structures of variants of a class 3 intein from Mycobacterium chimaera and molecular dynamics simulations, which suggested that the class 3 intein utilizes a different splicing mechanism from that of class 1 and 2 inteins. The class 3 intein uses a bond cleavage strategy reminiscent of proteases but share the same Hedgehog/INTein (HINT) fold of other intein classes. Engineering of class 3 inteins from a class 1 intein indicated that a class 3 intein would unlikely evolve directly from a class 1 or 2 intein. The HINT fold appears as structural and functional solution for trans-peptidyl and trans-esterification reactions commonly exploited by diverse mechanisms using different combinations of amino-acid types for the active-site residues.
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Affiliation(s)
- Hannes M. Beyer
- Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland; (H.M.B.); (S.I.V.); (A.S.A.); (K.M.M.); (O.H.S.O.)
| | - Salla I. Virtanen
- Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland; (H.M.B.); (S.I.V.); (A.S.A.); (K.M.M.); (O.H.S.O.)
| | - A. Sesilja Aranko
- Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland; (H.M.B.); (S.I.V.); (A.S.A.); (K.M.M.); (O.H.S.O.)
| | - Kornelia M. Mikula
- Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland; (H.M.B.); (S.I.V.); (A.S.A.); (K.M.M.); (O.H.S.O.)
| | - George T. Lountos
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA;
| | - Alexander Wlodawer
- Macromolecular Crystallography Laboratory, National Cancer Institute, Frederick, MD 21702, USA;
| | - O. H. Samuli Ollila
- Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland; (H.M.B.); (S.I.V.); (A.S.A.); (K.M.M.); (O.H.S.O.)
| | - Hideo Iwaï
- Institute of Biotechnology, University of Helsinki, P.O. Box 65, FIN-00014 Helsinki, Finland; (H.M.B.); (S.I.V.); (A.S.A.); (K.M.M.); (O.H.S.O.)
- Correspondence: ; Tel.: +358-2941-59752
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8
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Hoffmann S, Terhorst TME, Singh RK, Kümmel D, Pietrokovski S, Mootz HD. Biochemical and Structural Characterization of an Unusual and Naturally Split Class 3 Intein. Chembiochem 2020; 22:364-373. [PMID: 32813312 PMCID: PMC7891396 DOI: 10.1002/cbic.202000509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/19/2020] [Indexed: 12/31/2022]
Abstract
Split inteins are indispensable tools for protein engineering because their ligation and cleavage reactions enable unique modifications of the polypeptide backbone. Three different classes of inteins have been identified according to the nature of the covalent intermediates resulting from the acyl rearrangements in the multistep protein‐splicing pathway. Class 3 inteins employ a characteristic internal cysteine for a branched thioester intermediate. A bioinformatic database search of non‐redundant protein sequences revealed the absence of split variants in 1701 class 3 inteins. We have discovered the first reported split class 3 intein in a metagenomics data set and report its biochemical, mechanistic and structural analysis. The AceL NrdHF intein exhibits low sequence conservation with other inteins and marked deviations in residues at conserved key positions, including a variation of the typical class‐3 WCT triplet motif. Nevertheless, functional analysis confirmed the class 3 mechanism of the intein and revealed excellent splicing yields within a few minutes over a wide range of conditions and with barely detectable cleavage side reactions. A high‐resolution crystal structure of the AceL NrdHF precursor and a mutagenesis study explained the importance and roles of several residues at the key positions. Tolerated substitutions in the flanking extein residues and a high affinity between the split intein fragments further underline the intein's future potential as a ligation tool.
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Affiliation(s)
- Simon Hoffmann
- Institute of Biochemistry, University of Muenster, Corrensstraße 36, 48149, Münster, Germany
| | - Tobias M E Terhorst
- Institute of Biochemistry, University of Muenster, Corrensstraße 36, 48149, Münster, Germany
| | - Rohit K Singh
- Institute of Biochemistry, University of Muenster, Corrensstraße 36, 48149, Münster, Germany
| | - Daniel Kümmel
- Institute of Biochemistry, University of Muenster, Corrensstraße 36, 48149, Münster, Germany
| | - Shmuel Pietrokovski
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Henning D Mootz
- Institute of Biochemistry, University of Muenster, Corrensstraße 36, 48149, Münster, Germany
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Kelley DS, Lennon CW, Li Z, Miller MR, Banavali NK, Li H, Belfort M. Mycobacterial DnaB helicase intein as oxidative stress sensor. Nat Commun 2018; 9:4363. [PMID: 30341292 PMCID: PMC6195587 DOI: 10.1038/s41467-018-06554-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 09/10/2018] [Indexed: 11/09/2022] Open
Abstract
Inteins are widespread self-splicing protein elements emerging as potential post-translational environmental sensors. Here, we describe two inteins within one protein, the Mycobacterium smegmatis replicative helicase DnaB. These inteins, DnaBi1 and DnaBi2, have homology to inteins in pathogens, splice with vastly varied rates, and are differentially responsive to environmental stressors. Whereas DnaBi1 splicing is reversibly inhibited by oxidative and nitrosative insults, DnaBi2 is not. Using a reporter that measures splicing in a native intein-containing organism and western blotting, we show that H2O2 inhibits DnaBi1 splicing in M. smegmatis. Intriguingly, upon oxidation, the catalytic cysteine of DnaBi1 forms an intramolecular disulfide bond. We report a crystal structure of the class 3 DnaBi1 intein at 1.95 Å, supporting our findings and providing insight into this splicing mechanism. We propose that this cysteine toggle allows DnaBi1 to sense stress, pausing replication to maintain genome integrity, and then allowing splicing immediately when permissive conditions return.
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Affiliation(s)
- Danielle S Kelley
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, 12222, USA
| | - Christopher W Lennon
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY, 12222, USA
| | - Zhong Li
- Wadsworth Center, New York State Department of Health, 120 New Scotland Ave, Albany, NY, 12208, USA
| | - Michael R Miller
- Department of Chemistry, University at Albany, Albany, NY, 12222, USA
| | - Nilesh K Banavali
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, 12222, USA
- Wadsworth Center, New York State Department of Health, 120 New Scotland Ave, Albany, NY, 12208, USA
| | - Hongmin Li
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, 12222, USA.
- Wadsworth Center, New York State Department of Health, 120 New Scotland Ave, Albany, NY, 12208, USA.
| | - Marlene Belfort
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY, 12222, USA.
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY, 12222, USA.
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Buttimer C, Born Y, Lucid A, Loessner MJ, Fieseler L, Coffey A. Erwinia amylovora phage vB_EamM_Y3 represents another lineage of hairy Myoviridae. Res Microbiol 2018; 169:505-514. [PMID: 29777834 DOI: 10.1016/j.resmic.2018.04.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 04/23/2018] [Indexed: 10/16/2022]
Abstract
To date, a small number of jumbo myoviruses have been reported to possess atypical whisker-like structures along the surface of their contractile tails. Erwinia amylovora phage vB_EamM_Y3 is another example. It possesses a genome of 261,365 kbp with 333 predicted ORFs. Using a combination of BLASTP, Interproscan and HHpred, about 21% of its putative proteins could be assigned functions involved in nucleotide metabolism, DNA replication, virion structure and cell wall degradation. The phage was found to have a signal-arrest-release (SAR) endolysin (Y3_301) possessing a soluble lytic transglycosylase domain. Like other SAR endolysins, inducible expression of Y3_301 caused Escherichia coli lysis, which is dependent on the presence of an N-terminal signal sequence. Phylogenetic analysis showed that its closest relatives are other jumbo phages including Pseudomonas aeruginosa phage PaBG and P. putida phage Lu11, sharing 105 and 87 homologous proteins respectively. Like these phages, Y3 also shares a distant relationship to Ralstonia solanacearum phage ΦRSL1 (sharing 55 homologous proteins). As these phages are unrelated to the Rak2-like group of hairy phages, Y3 along with Lu11 represent a second lineage of hairy myoviruses.
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Affiliation(s)
- Colin Buttimer
- Department of Biological Sciences, Cork Institute of Technology, Cork, Ireland.
| | - Yannick Born
- Institute of Food, Nutrition, and Health, ETH Zurich, Zürich, Switzerland; Agroscope, Research Division Plant Protection, Wädenswil, Switzerland.
| | - Alan Lucid
- Department of Biological Sciences, Cork Institute of Technology, Cork, Ireland
| | - Martin J Loessner
- Institute of Food, Nutrition, and Health, ETH Zurich, Zürich, Switzerland.
| | - Lars Fieseler
- Institute of Food, Nutrition, and Health, ETH Zurich, Zürich, Switzerland.
| | - Aidan Coffey
- Department of Biological Sciences, Cork Institute of Technology, Cork, Ireland; APC Microbiome Institute, University College, Cork, Ireland.
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11
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Gordo V, Aparicio D, Pérez-Luque R, Benito A, Vilanova M, Usón I, Fita I, Ribó M. Structural Insights into Subunits Assembly and the Oxyester Splicing Mechanism of Neq pol Split Intein. Cell Chem Biol 2018; 25:871-879.e2. [PMID: 29754955 DOI: 10.1016/j.chembiol.2018.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 02/28/2018] [Accepted: 04/08/2018] [Indexed: 11/28/2022]
Abstract
Split inteins are expressed as two separated subunits (N-intein and C-intein) fused to the corresponding exteins. The specific association of both intein subunits precedes protein splicing, which results in excision of the intein subunits and in ligation, by a peptide bond, of the concomitant exteins. Catalytically active intein precursors are typically too reactive for crystallization or even isolation. Neq pol is the trans-intein of the B-type DNA polymerase I split gene from hyperthermophile Nanoarchaeum equitans. We have determined the crystal structures of both the isolated NeqN and the complex of NeqN and NeqC subunits carrying the wild-type sequences, including the essential catalytic residues Ser1 and Thr+1, in addition to seven and three residues of the N- and C-exteins, respectively. These structures provide detailed information on the unique oxyester chemistry of the splicing mechanism of Neq pol and of the extensive rearrangements that occur in NeqN during the association step.
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Affiliation(s)
- Verónica Gordo
- Laboratori d'Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Universitat de Girona, C/ Maria Aurèlia Capmany 40, 17003 Girona, Spain; IdIBGi Hospital Universitari Josep Trueta, Girona, Spain
| | - David Aparicio
- Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Parc Cientific de Barcelona, Baldiri i Reixac 10, 08028 Barcelona, Spain
| | - Rosa Pérez-Luque
- Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Parc Cientific de Barcelona, Baldiri i Reixac 10, 08028 Barcelona, Spain
| | - Antoni Benito
- Laboratori d'Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Universitat de Girona, C/ Maria Aurèlia Capmany 40, 17003 Girona, Spain; IdIBGi Hospital Universitari Josep Trueta, Girona, Spain
| | - Maria Vilanova
- Laboratori d'Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Universitat de Girona, C/ Maria Aurèlia Capmany 40, 17003 Girona, Spain; IdIBGi Hospital Universitari Josep Trueta, Girona, Spain
| | - Isabel Usón
- Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Parc Cientific de Barcelona, Baldiri i Reixac 10, 08028 Barcelona, Spain; ICREA Lluís Companys 23, 08003 Barcelona, Spain
| | - Ignacio Fita
- Instituto de Biología Molecular de Barcelona (IBMB-CSIC), Parc Cientific de Barcelona, Baldiri i Reixac 10, 08028 Barcelona, Spain.
| | - Marc Ribó
- Laboratori d'Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Universitat de Girona, C/ Maria Aurèlia Capmany 40, 17003 Girona, Spain; IdIBGi Hospital Universitari Josep Trueta, Girona, Spain.
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12
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Mujika JI, Lopez X. Unveiling the Catalytic Role of B-Block Histidine in the N–S Acyl Shift Step of Protein Splicing. J Phys Chem B 2017; 121:7786-7796. [DOI: 10.1021/acs.jpcb.7b04276] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J. I. Mujika
- Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi Spain
| | - X. Lopez
- Kimika Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU) and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi Spain
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13
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Buttimer C, Hendrix H, Oliveira H, Casey A, Neve H, McAuliffe O, Ross RP, Hill C, Noben JP, O'Mahony J, Lavigne R, Coffey A. Things Are Getting Hairy: Enterobacteria Bacteriophage vB_PcaM_CBB. Front Microbiol 2017; 8:44. [PMID: 28174560 PMCID: PMC5259590 DOI: 10.3389/fmicb.2017.00044] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/06/2017] [Indexed: 11/30/2022] Open
Abstract
Enterobacteria phage vB_PcaM_CBB is a "jumbo" phage belonging to the family Myoviridae. It possesses highly atypical whisker-like structures along the length of its contractile tail. It has a broad host range with the capability of infecting species of the genera Erwinia, Pectobacterium, and Cronobacter. With a genome of 355,922 bp, excluding a predicted terminal repeat of 22,456 bp, phage CBB is the third largest phage sequenced to date. Its genome was predicted to encode 554 ORFs with 33 tRNAs. Based on prediction and proteome analysis of the virions, 29% of its predicted ORFs could be functionally assigned. Protein comparison shows that CBB shares between 33-38% of its proteins with Cronobacter phage GAP32, coliphages PBECO4 and 121Q as well as Klebsiella phage vB_KleM_Rak2. This work presents a detailed and comparative analysis of vB_PcaM_CBB of a highly atypical jumbo myoviridae phage, contributing to a better understanding of phage diversity and biology.
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Affiliation(s)
- Colin Buttimer
- Department of Biological Sciences, Cork Institute of TechnologyCork, Ireland
| | - Hanne Hendrix
- Laboratory of Gene Technology, KU LeuvenLeuven, Belgium
| | - Hugo Oliveira
- Laboratório de Investigação em Biofilmes Rosário Oliveira, Centre of Biological Engineering, University of MinhoBraga, Portugal
| | - Aidan Casey
- Teagasc Food Research Centre, Moorepark Fermoy, Co.Cork, Ireland
| | - Horst Neve
- Department of Microbiology and Biotechnology, Max Rubner-InstitutKiel, Germany
| | - Olivia McAuliffe
- Teagasc Food Research Centre, Moorepark Fermoy, Co.Cork, Ireland
| | - R. Paul Ross
- Teagasc Food Research Centre, Moorepark Fermoy, Co.Cork, Ireland
| | - Colin Hill
- APC Microbiome Institute and School of Microbiology, University CollegeCork, Ireland
| | - Jean-Paul Noben
- Biomedical Research Institute and Transnational University Limburg, Hasselt UniversityDiepenbeek, Belgium
| | - Jim O'Mahony
- Department of Biological Sciences, Cork Institute of TechnologyCork, Ireland
| | - Rob Lavigne
- Laboratory of Gene Technology, KU LeuvenLeuven, Belgium
| | - Aidan Coffey
- Department of Biological Sciences, Cork Institute of TechnologyCork, Ireland
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14
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Tori K, Perler F. Sequential formation of two branched intermediates during protein splicing of class three inteins. Extremophiles 2016; 21:41-49. [PMID: 27704298 PMCID: PMC5222942 DOI: 10.1007/s00792-016-0876-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 09/24/2016] [Indexed: 11/25/2022]
Abstract
Inteins are the protein equivalent of introns. They are seamlessly removed during post-translational maturation of their host protein (extein). Inteins from extremophiles played a key role in understanding intein-mediated protein splicing. There are currently three classes of inteins defined by catalytic mechanism and sequence signatures. This study demonstrates splicing of three class 3 mini-inteins: Burkholderia vietnamiensis G4 Bvi IcmO intein, Mycobacterium smegmatis MC2 155 Msm DnaB-1 intein and Mycobacterium leprae strain TN Mle DnaB intein. B. vietnamiensis has a broad ecological range and remediates trichloroethene. M. smegmatis is a biofilm forming soil bacteria. Although other intein classes have only a single branched intermediate at the C-terminal splice junction, the class 3 intein reaction pathway includes two branched intermediates. The class 3 specific branched intermediate is formed by an internal cysteine, while the C-terminal branch intermediate is at a serine or threonine in all class 3 inteins except the Bvi IcmO intein, where it is a cysteine. This latter cysteine was unable to compensate for mutation of the class 3-specific internal catalytic cysteine despite the Bvi IcmO intein having an N-terminal splice junction naturally tuned for a cysteine nucleophile, demonstrating the mandatory order of branch intermediates in class 3 inteins.
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Affiliation(s)
- Kazuo Tori
- New England Biolabs, Inc., Ipswich, MA 01938 USA
- Takara Bio USA, Inc., 1290 Terra Bella Ave., Mountain View, CA 94043 USA
| | - Francine Perler
- New England Biolabs, Inc., Ipswich, MA 01938 USA
- Perls of Wisdom Biotech Consulting, Brookline, MA 02446 USA
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520 USA
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15
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Abstract
Inteins are self-splicing protein elements that are mobile at the DNA level and are sporadically distributed across microbial genomes. Inteins appear to be horizontally transferred, and it has been speculated that phages may play a role in intein distribution. Our attention turns to mycobacteriophages, which infect mycobacteria, where both phage and host harbor inteins. Using bioinformatics, mycobacteriophage genomes were mined for inteins. This study reveals that these mobile elements are present across multiple mycobacteriophage clusters and are pervasive in certain genes, like the large terminase subunit TerL and a RecB-like nuclease, with the majority of intein-containing genes being phage specific. Strikingly, despite this phage specificity, inteins localize to functional motifs shared with bacteria, such that intein-containing genes have similar roles, like hydrolase activity and nucleic acid binding, indicating a global commonality among intein-hosting proteins. Additionally, there are multiple insertion points within active centers, implying independent invasion events, with regulatory implications. Several phage inteins were shown to be splicing competent and to encode functional homing endonucleases, important for mobility. Further, bioinformatic analysis supports the potential for phages as facilitators of intein movement among mycobacteria and related genera. Analysis of catalytic intein residues finds the highly conserved penultimate histidine inconsistently maintained among mycobacteriophages. Biochemical characterization of a noncanonical phage intein shows that this residue influences precursor accumulation, suggesting that splicing has been tuned in phages to modulate generation of important proteins. Together, this work expands our understanding of phage-based intein dissemination and evolution and implies that phages provide a context for evolution of splicing-based regulation. Inteins are mobile protein splicing elements found in critical genes across all domains of life. Mycobacterial inteins are of particular interest because of their occurrence in pathogenic species, such as Mycobacterium tuberculosis and Mycobacterium leprae, which harbor inteins in important proteins. We have discovered a similarity in activities of intein-containing proteins among mycobacteriophages and their intein-rich actinobacterial hosts, with implications for both posttranslational regulation by inteins and phages participating in horizontal intein transfer. Our demonstration of multiple insertion points within active centers of phage proteins implies independent invasion events, indicating the importance of intein maintenance at specific functional sites. The variable conservation of a catalytic splicing residue, leading to profoundly altered splicing rates, points to the regulatory potential of inteins and to mycobacteriophages playing a role in intein evolution. Collectively, these results suggest inteins as posttranslational regulators and mycobacteriophages as both vehicles for intein distribution and incubators for intein evolution.
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16
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Abstract
Inteins are nature's escape artists; they facilitate their excision from flanking polypeptides (exteins) concomitant with extein ligation to produce a mature host protein. Splicing requires sequential nucleophilic displacement reactions catalyzed by strategies similar to proteases and asparagine lyases. Inteins require precise reaction coordination rather than rapid turnover or tight substrate binding because they are single turnover enzymes with covalently linked substrates. This has allowed inteins to explore alternative mechanisms with different steps or to use different methods for activation and coordination of the steps. Pressing issues include understanding the underlying details of catalysis and how the splicing steps are controlled.
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Affiliation(s)
- Kenneth V Mills
- From the Department of Chemistry, College of the Holy Cross, Worcester, Massachusetts 01610
| | - Margaret A Johnson
- the Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama 35294, and
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17
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Abstract
ABSTRACT
Mycobacteriophages have provided numerous essential tools for mycobacterial genetics, including delivery systems for transposons, reporter genes, and allelic exchange substrates, and components for plasmid vectors and mutagenesis. Their genetically diverse genomes also reveal insights into the broader nature of the phage population and the evolutionary mechanisms that give rise to it. The substantial advances in our understanding of the biology of mycobacteriophages including a large collection of completely sequenced genomes indicates a rich potential for further contributions in tuberculosis genetics and beyond.
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18
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Hatfull GF. Molecular Genetics of Mycobacteriophages. Microbiol Spectr 2014; 2:1-36. [PMID: 25328854 PMCID: PMC4199240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023] Open
Abstract
Mycobacteriophages have provided numerous essential tools for mycobacterial genetics, including delivery systems for transposons, reporter genes, and allelic exchange substrates, and components for plasmid vectors and mutagenesis. Their genetically diverse genomes also reveal insights into the broader nature of the phage population and the evolutionary mechanisms that give rise to it. The substantial advances in our understanding of the biology of mycobacteriophages including a large collection of completely sequenced genomes indicates a rich potential for further contributions in tuberculosis genetics and beyond.
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Affiliation(s)
- Graham F Hatfull
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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19
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Jordan TC, Burnett SH, Carson S, Caruso SM, Clase K, DeJong RJ, Dennehy JJ, Denver DR, Dunbar D, Elgin SCR, Findley AM, Gissendanner CR, Golebiewska UP, Guild N, Hartzog GA, Grillo WH, Hollowell GP, Hughes LE, Johnson A, King RA, Lewis LO, Li W, Rosenzweig F, Rubin MR, Saha MS, Sandoz J, Shaffer CD, Taylor B, Temple L, Vazquez E, Ware VC, Barker LP, Bradley KW, Jacobs-Sera D, Pope WH, Russell DA, Cresawn SG, Lopatto D, Bailey CP, Hatfull GF. A broadly implementable research course in phage discovery and genomics for first-year undergraduate students. mBio 2014; 5:e01051-13. [PMID: 24496795 DOI: 10.1128/mbio.01051-13.editor] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
UNLABELLED Engaging large numbers of undergraduates in authentic scientific discovery is desirable but difficult to achieve. We have developed a general model in which faculty and teaching assistants from diverse academic institutions are trained to teach a research course for first-year undergraduate students focused on bacteriophage discovery and genomics. The course is situated within a broader scientific context aimed at understanding viral diversity, such that faculty and students are collaborators with established researchers in the field. The Howard Hughes Medical Institute (HHMI) Science Education Alliance Phage Hunters Advancing Genomics and Evolutionary Science (SEA-PHAGES) course has been widely implemented and has been taken by over 4,800 students at 73 institutions. We show here that this alliance-sourced model not only substantially advances the field of phage genomics but also stimulates students' interest in science, positively influences academic achievement, and enhances persistence in science, technology, engineering, and mathematics (STEM) disciplines. Broad application of this model by integrating other research areas with large numbers of early-career undergraduate students has the potential to be transformative in science education and research training. IMPORTANCE Engagement of undergraduate students in scientific research at early stages in their careers presents an opportunity to excite students about science, technology, engineering, and mathematics (STEM) disciplines and promote continued interests in these areas. Many excellent course-based undergraduate research experiences have been developed, but scaling these to a broader impact with larger numbers of students is challenging. The Howard Hughes Medical Institute (HHMI) Science Education Alliance Phage Hunting Advancing Genomics and Evolutionary Science (SEA-PHAGES) program takes advantage of the huge size and diversity of the bacteriophage population to engage students in discovery of new viruses, genome annotation, and comparative genomics, with strong impacts on bacteriophage research, increased persistence in STEM fields, and student self-identification with learning gains, motivation, attitude, and career aspirations.
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20
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A broadly implementable research course in phage discovery and genomics for first-year undergraduate students. mBio 2014; 5:e01051-13. [PMID: 24496795 PMCID: PMC3950523 DOI: 10.1128/mbio.01051-13] [Citation(s) in RCA: 321] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
UNLABELLED Engaging large numbers of undergraduates in authentic scientific discovery is desirable but difficult to achieve. We have developed a general model in which faculty and teaching assistants from diverse academic institutions are trained to teach a research course for first-year undergraduate students focused on bacteriophage discovery and genomics. The course is situated within a broader scientific context aimed at understanding viral diversity, such that faculty and students are collaborators with established researchers in the field. The Howard Hughes Medical Institute (HHMI) Science Education Alliance Phage Hunters Advancing Genomics and Evolutionary Science (SEA-PHAGES) course has been widely implemented and has been taken by over 4,800 students at 73 institutions. We show here that this alliance-sourced model not only substantially advances the field of phage genomics but also stimulates students' interest in science, positively influences academic achievement, and enhances persistence in science, technology, engineering, and mathematics (STEM) disciplines. Broad application of this model by integrating other research areas with large numbers of early-career undergraduate students has the potential to be transformative in science education and research training. IMPORTANCE Engagement of undergraduate students in scientific research at early stages in their careers presents an opportunity to excite students about science, technology, engineering, and mathematics (STEM) disciplines and promote continued interests in these areas. Many excellent course-based undergraduate research experiences have been developed, but scaling these to a broader impact with larger numbers of students is challenging. The Howard Hughes Medical Institute (HHMI) Science Education Alliance Phage Hunting Advancing Genomics and Evolutionary Science (SEA-PHAGES) program takes advantage of the huge size and diversity of the bacteriophage population to engage students in discovery of new viruses, genome annotation, and comparative genomics, with strong impacts on bacteriophage research, increased persistence in STEM fields, and student self-identification with learning gains, motivation, attitude, and career aspirations.
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21
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Intermolecular domain swapping induces intein-mediated protein alternative splicing. Nat Chem Biol 2013; 9:616-22. [DOI: 10.1038/nchembio.1320] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 07/17/2013] [Indexed: 11/09/2022]
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22
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Nicastri MC, Xega K, Li L, Xie J, Wang C, Linhardt RJ, Reitter JN, Mills KV. Internal disulfide bond acts as a switch for intein activity. Biochemistry 2013; 52:5920-7. [PMID: 23906287 DOI: 10.1021/bi400736c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Inteins are intervening polypeptides that catalyze their own removal from flanking exteins, concomitant to the ligation of the exteins. The intein that interrupts the DP2 (large) subunit of DNA polymerase II from Methanoculleus marisnigri (Mma) can promote protein splicing. However, protein splicing can be prevented or reduced by overexpression under nonreducing conditions because of the formation of a disulfide bond between two internal intein Cys residues. This redox sensitivity leads to differential activity in different strains of E. coli as well as in different cell compartments. The redox-dependent control of in vivo protein splicing in an intein derived from an anaerobe that can occupy multiple environments hints at a possible physiological role for protein splicing.
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Affiliation(s)
- Michael C Nicastri
- Department of Chemistry, College of the Holy Cross, Worcester, Massachusetts 01610, United States
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23
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Aranko AS, Oeemig JS, Iwaï H. Structural basis for proteintrans-splicing by a bacterial intein-like domain - protein ligation without nucleophilic side chains. FEBS J 2013; 280:3256-69. [DOI: 10.1111/febs.12307] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/17/2013] [Accepted: 04/22/2013] [Indexed: 12/01/2022]
Affiliation(s)
- A. Sesilja Aranko
- Research Program in Structural Biology and Biophysics; Institute of Biotechnology; University of Helsinki; Finland
| | - Jesper S. Oeemig
- Research Program in Structural Biology and Biophysics; Institute of Biotechnology; University of Helsinki; Finland
| | - Hideo Iwaï
- Research Program in Structural Biology and Biophysics; Institute of Biotechnology; University of Helsinki; Finland
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24
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Volkmann G, Mootz HD. Recent progress in intein research: from mechanism to directed evolution and applications. Cell Mol Life Sci 2013; 70:1185-206. [PMID: 22926412 PMCID: PMC11113529 DOI: 10.1007/s00018-012-1120-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 07/23/2012] [Accepted: 08/06/2012] [Indexed: 10/27/2022]
Abstract
Inteins catalyze a post-translational modification known as protein splicing, where the intein removes itself from a precursor protein and concomitantly ligates the flanking protein sequences with a peptide bond. Over the past two decades, inteins have risen from a peculiarity to a rich source of applications in biotechnology, biomedicine, and protein chemistry. In this review, we focus on developments of intein-related research spanning the last 5 years, including the three different splicing mechanisms and their molecular underpinnings, the directed evolution of inteins towards improved splicing in exogenous protein contexts, as well as novel applications of inteins for cell biology and protein engineering, which were made possible by a clearer understanding of the protein splicing mechanism.
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Affiliation(s)
- Gerrit Volkmann
- Institute of Biochemistry, University of Münster, Wilhelm-Klemm-Str. 2, 48149 Münster, Germany
| | - Henning D. Mootz
- Institute of Biochemistry, University of Münster, Wilhelm-Klemm-Str. 2, 48149 Münster, Germany
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25
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Tori K, Cheriyan M, Pedamallu CS, Contreras MA, Perler FB. The Thermococcus kodakaraensis Tko CDC21-1 intein activates its N-terminal splice junction in the absence of a conserved histidine by a compensatory mechanism. Biochemistry 2012; 51:2496-505. [PMID: 22380677 DOI: 10.1021/bi201840k] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Inteins and other self-catalytic enzymes, such as glycosylasparaginases and hedgehog precursors, initiate autocleavage by converting a peptide bond to a (thio)ester bond when Ser, Thr, or Cys undergoes an N-[S/O] acyl migration assisted by residues within the precursor. Previous studies have shown that a His at position 10 in intein Block B is essential for this initial acyl migration and N-terminal splice junction cleavage. This His is present in all inteins identified to date except the Thermococcus kodakaraensis Tko CDC21-1 intein orthologs and the inactive Arthrobacter species FB24 Arth_1007 intein. This study demonstrates that the Tko CDC21-1 intein is fully active and has replaced the lost catalytic function normally provided by the Block B His using a compensatory mechanism involving a conserved ortholog-specific basic residue (Lys(58)) present outside the standard intein conserved motifs. We propose that Lys(58) catalyzes the initial N-S acyl migration by stabilizing the thiazolidine-tetrahedral intermediate, allowing it to be resolved by water-mediated hydrolysis rather than by protonating the leaving group as His is theorized to do in many other inteins. Autoprocessing enzymes may have more flexibility in evolving catalytic variations because high reaction rates are not required when performing single-turnover reactions on "substrates" that are covalently attached to the enzyme. Consequently, inteins have more flexibility to sample catalytic mechanisms, providing insight into various strategies that enzymes use to accomplish catalysis.
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Affiliation(s)
- Kazuo Tori
- New England BioLabs, Ipswich, Massachusetts 01938, United States
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26
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Mujika JI, Lopez X, Mulholland AJ. Mechanism of C-terminal intein cleavage in protein splicing from QM/MM molecular dynamics simulations. Org Biomol Chem 2011; 10:1207-18. [PMID: 22179261 DOI: 10.1039/c1ob06444d] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Protein splicing is a post-translational process in which a biologically inactive protein is activated by the release of a segment denoted as an intein. The process involves four steps. In the third, the scission of the intein takes place after the cyclization of the last amino acid of the segment, an asparagine. Little is known about the chemical reaction necessary for this cyclization. Experiments demonstrate that two histidines (the penultimate amino acid of the intein, and a histidine located 10 amino acids upstream) are relevant in the cyclization of the asparagine. We have investigated the mechanism and determinants of reaction in the GyrA intein focusing on the requirements for asparagine activation for its cyclization. First, the influence that the protonation states of these two histidines have on the orientation of the asparagine side chain is investigated by means of molecular dynamics simulation. Molecular dynamics simulations using the CHARMM27 force field were carried out on the three possible protonation states for each of these two histidines. The results indicate that the only protonation state in which the conformation of the system is suitable for cyclization is when the penultimate histidine is fully protonated (positively charged), and the upstream histidine is in the His(ε) neutral tautomeric form. The free energy profile for the reaction in which the asparagine is activated by a proton transfer to the upstream histidine is presented, computed by hybrid quantum mechanics/molecular mechanics (QM/MM) umbrella sampling molecular dynamics at the SCCDFTB/CHARMM27 level of theory. The calculated free energy barrier for the reaction is 19.0 kcal mol(-1). B3LYP/6-31+G(d) QM/MM single-point calculations give a qualitatively a similar energy profile, although with somewhat higher energy barriers, in good agreement with the value derived from experiment of 25 kcal mol(-1) at 60 °C. QM/MM molecular dynamics simulations of the reactant, activated reactant and intermediate states highlight the importance of the Arg181-Val182-Asp183 segment in catalysing the reaction. Overall, the results indicate that nucleophilic activation of the asparagine for its cyclization by the upstream histidine acting as the base is a plausible mechanism for the C-terminal cleavage in protein splicing.
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Affiliation(s)
- Jon I Mujika
- Kimika Fakultatea, Euskal Herriko Unibertsitatea and Donostia International Physics Center (DIPC, P. K. 1072, 20080, Donostia, Euskadi, Spain.
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27
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Tori K, Perler FB. The Arthrobacter species FB24 Arth_1007 (DnaB) intein is a pseudogene. PLoS One 2011; 6:e26361. [PMID: 22028863 PMCID: PMC3196547 DOI: 10.1371/journal.pone.0026361] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 09/25/2011] [Indexed: 02/05/2023] Open
Abstract
An Arthrobacter species FB24 gene (locus tag Arth_1007) was previously annotated as a putative intein-containing DnaB helicase of phage origin (Arsp-FB24 DnaB intein). However, it is not a helicase gene because the sequence similarity is limited to inteins. In fact, the flanking exteins total only 66 amino acids. Therefore, the intein should be referred to as the Arsp-FB24 Arth_1007 intein. The Arsp-FB24 Arth_1007 intein failed to splice in its native precursor and in a model precursor. We previously noted that the Arsp-FB24 Arth_1007 intein is the only putative Class 3 intein that is missing the catalytically essential Cys at position 4 of intein Motif F, which is one of the three defining signature residues of this class. Additionally, a catalytically essential His in position 10 of intein Motif B is also absent; this His is the most conserved residue amongst all inteins. Splicing activity was not rescued when these two catalytically important positions were 'reverted' back to their consensus residues. This study restores the unity of the Class 3 intein signature sequence in active inteins by demonstrating that the Arsp-FB24 Arth_1007 intein is an inactive pseudogene.
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Affiliation(s)
- Kazuo Tori
- New England Biolabs, Inc., Ipswich, Massachusetts, United States of America
| | - Francine B. Perler
- New England Biolabs, Inc., Ipswich, Massachusetts, United States of America
- * E-mail:
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