1
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Tharappel AM, Li Z, Zhu YC, Wu X, Chaturvedi S, Zhang QY, Li H. Calcimycin Inhibits Cryptococcus neoformans In Vitro and In Vivo by Targeting the Prp8 Intein Splicing. ACS Infect Dis 2022; 8:1851-1868. [PMID: 35948057 PMCID: PMC9464717 DOI: 10.1021/acsinfecdis.2c00137] [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: 01/29/2023]
Abstract
Drug resistance is a significant concern in the treatment of diseases, including cryptococcosis caused by Cryptococcus neoformans (Cne) and Cryptococcus gattii (Cga). Alternative drug targets are necessary to overcome drug resistance before it attains a critical stage. Splicing of inteins from pro-protein precursors is crucial for activities of essential proteins hosting intein elements in many organisms, including human pathogens such as Cne and Cga. Through a high-throughput screening, we identified calcimycin (CMN) as a potent Prp8 intein splicing inhibitor with a minimum inhibitory concentration (MIC) of 1.5 μg/mL against the wild-type Cne-H99 (Cne-WT or Cne). In contrast, CMN inhibited the intein-less mutant strain (Cne-Mut) with a 16-fold higher MIC. Interestingly, Aspergillus fumigatus and a few Candida species were resistant to CMN. Further studies indicated that CMN reduced virulence factors such as urease activity, melanin production, and biofilm formation in Cne. CMN also inhibited Cne intracellular infection in macrophages. In a target-specific split nanoluciferase assay, the IC50 of CMN was 4.6 μg/mL. Binding of CMN to recombinant Prp8 intein was demonstrated by thermal shift assay and microscale thermophoresis. Treating Cne cells with CMN reduced intein splicing. CMN was fungistatic and showed a synergistic effect with the known antifungal drug amphotericin B. Finally, CMN treatment at 20 mg/kg body weight led to 60% reduction in lung fungal load in a cryptococcal pulmonary infection mouse model. Overall, CMN represents a potent antifungal with a novel mechanism of action to treat Cne and possibly Cga infections.
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Affiliation(s)
- Anil Mathew Tharappel
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Zhong Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Yan Chun Zhu
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Xiangmeng Wu
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
| | - Sudha Chaturvedi
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Qing-Yu Zhang
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
| | - Hongmin Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
- The BIO5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
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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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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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4
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Boral S, Maiti S, Basak AJ, Lee W, De S. Structural, Dynamic, and Functional Characterization of a DnaX Mini-intein Derived from Spirulina platensis Provides Important Insights into Intein-Mediated Catalysis of Protein Splicing. Biochemistry 2020; 59:4711-4724. [PMID: 33289560 DOI: 10.1021/acs.biochem.0c00828] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein splicing is a self-catalyzed post-translational modification in which the intein enzyme excises itself from a precursor protein and ligates the flanking sequences to produce a mature protein. We report the solution structure of a 136-residue DnaX mini-intein enzyme derived from the cyanobacterium Spirulina platensis. This sequence adopts a well-defined globular structure and forms a horseshoe-shaped fold commonly found in the HINT (hedgehog intein) topology. Backbone dynamics and hydrogen exchange experiments revealed conserved motions on various time scales, which is proposed to be a characteristic of the intein fold. Interestingly, several dynamic motions were found in symmetrically equivalent positions within the protein structure, which might be a consequence of the symmetrical intein fold. In cell splicing activity showed that Spl DnaX mini-intein is a highly active enzyme. The precursor protein was not detected at any timepoint of the assay. Apart from the splicing reaction, catalytic cleavage at the N- and C-termini of the precursor protein was also observed. To determine the roles of the catalytic residues in splicing and cleavage reactions, all combinations of alanine mutations of these residues were generated and functionally characterized. This in-depth analysis revealed cooperativity between these catalytic residues, which suppresses the N- and C-terminal cleavage reactions and enhances the yield of the spliced product. Overall, this study provides a thorough structural, dynamic, and functional characterization of a new intein sequence and adds to the collection of these unique enzymes that have found tremendous applications in biochemistry and biotechnology.
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Affiliation(s)
- Soumendu Boral
- School of Bioscience, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Snigdha Maiti
- School of Bioscience, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Aditya J Basak
- School of Bioscience, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
| | - Woonghee Lee
- Department of Chemistry, University of Colorado Denver, Denver, Colorado 80217, United States
| | - Soumya De
- School of Bioscience, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India
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5
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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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6
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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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7
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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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8
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Woods D, Vangaveti S, Egbanum I, Sweeney AM, Li Z, Bacot-Davis V, LeSassier DS, Stanger M, Hardison GE, Li H, Belfort M, Lennon CW. Conditional DnaB Protein Splicing Is Reversibly Inhibited by Zinc in Mycobacteria. mBio 2020; 11:e01403-20. [PMID: 32665276 PMCID: PMC7360933 DOI: 10.1128/mbio.01403-20] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 06/09/2020] [Indexed: 11/20/2022] Open
Abstract
Inteins, as posttranslational regulatory elements, can tune protein function to environmental changes by conditional protein splicing (CPS). Translated as subdomains interrupting host proteins, inteins splice to scarlessly join flanking sequences (exteins). We used DnaB-intein1 (DnaBi1) from a replicative helicase of Mycobacterium smegmatis to build a kanamycin intein splicing reporter (KISR) that links splicing of DnaBi1 to kanamycin resistance. Using expression in heterologous Escherichia coli, we observed phenotypic classes of various levels of splicing-dependent resistance (SDR) and related these to the insertion position of DnaBi1 within the kanamycin resistance protein (KanR). The KanR-DnaBi1 construct demonstrating the most stringent SDR was used to probe for CPS of DnaB in the native host environment, M. smegmatis We show here that zinc, important during mycobacterial pathogenesis, inhibits DnaB splicing in M. smegmatis Using an in vitro reporter system, we demonstrated that zinc potently and reversibly inhibited DnaBi1 splicing, as well as splicing of a comparable intein from Mycobacterium leprae Finally, in a 1.95 Å crystal structure, we show that zinc inhibits splicing through binding to the very cysteine that initiates the splicing reaction. Together, our results provide compelling support for a model whereby mycobacterial DnaB protein splicing, and thus DNA replication, is responsive to environmental zinc.IMPORTANCE Inteins are present in a large fraction of prokaryotes and localize within conserved proteins, including the mycobacterial replicative helicase DnaB. In addition to their extensive protein engineering applications, inteins have emerged as environmentally responsive posttranslational regulators of the genes that encode them. While several studies have shown compelling evidence of conditional protein splicing (CPS), examination of splicing in the native host of the intein has proven to be challenging. Here, we demonstrated through a number of measures, including the use of a splicing-dependent sensor capable of monitoring intein activity in the native host, that zinc is a potent and reversible inhibitor of mycobacterial DnaB splicing. This work also expands our knowledge of site selection for intein insertion within nonnative proteins, demonstrating that splicing-dependent host protein activation correlates with proximity to the active site. Additionally, we surmise that splicing regulation by zinc has mycobacteriocidal and CPS application potential.
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Affiliation(s)
- Daniel Woods
- Department of Biological Sciences, University at Albany, Albany, New York, USA
| | - Sweta Vangaveti
- The RNA Institute, University at Albany, Albany, New York, USA
| | - Ikechukwu Egbanum
- Department of Biological Sciences, University at Albany, Albany, New York, USA
| | - Allison M Sweeney
- Department of Biology, Murray State University, Murray, Kentucky, USA
| | - Zhong Li
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Valjean Bacot-Davis
- Renaissance School of Medicine, Stony Brook University, Stony Brook, New York, USA
| | | | - Matthew Stanger
- Department of Biological Sciences, University at Albany, Albany, New York, USA
| | | | - Hongmin Li
- Department of Biological Sciences, University at Albany, Albany, New York, USA
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Marlene Belfort
- Department of Biological Sciences, University at Albany, Albany, New York, USA
- The RNA Institute, University at Albany, Albany, New York, USA
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9
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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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10
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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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11
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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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12
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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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13
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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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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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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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Expanding the definition of class 3 inteins and their proposed phage origin. J Bacteriol 2011; 193:2035-41. [PMID: 21317331 DOI: 10.1128/jb.01407-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inteins are the protein equivalent of introns. Their protein splicing activity is essential for the host protein's maturation and function. Inteins are grouped into three classes based on sequence signature and splicing mechanism. The sequence signature of the recently characterized class 3 inteins is a noncontiguous Trp-Cys-Thr (WCT) motif and the absence of the standard class 1 Cys¹ or Ser¹ N-terminal nucleophile. The intein N-terminal Cys¹ or Ser¹ residue is essential for splicing in class 1 inteins. The mycobacteriophage Catera Gp206, Nocardioides sp. strain JS614 TOPRIM, and Thermobifida fusca YX Tfu2914 inteins have a mixture of class 1 and class 3 motifs. They carry the class 3 Trp-Cys-Thr motif and have the standard class 1 N-terminal Ser¹ or Cys¹. This study determined which class the mycobacteriophage Catera Gp206 and Nocardioides sp. JS614 TOPRIM inteins belong to based on catalytic mechanism. The mycobacteriophage Catera Gp206 intein (starting with Ser¹) is a class 3 intein, and its Ser¹ residue is not required for splicing. Based on phylogenetic analysis, we propose that class 3 inteins arose from a single mutated intein that was spread by phage into predominantly helicase genes in various phages and their hosts.
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Canonical protein splicing of a class 1 intein that has a class 3 noncanonical sequence motif. J Bacteriol 2010; 193:994-7. [PMID: 21131486 DOI: 10.1128/jb.01287-10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A Thermobifida fusca intein has two characteristics of class 3 inteins: a noncontiguous covariant Trp-Cys-Thr triplet and a Ser flanking its C terminus. However, it has Cys at position one, characteristic of class 1 inteins. Splicing does not require the internal Cys, which may instead coordinate the active site. Therefore, the intein is class 1.
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