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Abstract
Encapsulins are a recently discovered class of prokaryotic self-assembling icosahedral protein nanocompartments measuring between 24 and 42 nm in diameter, capable of selectively encapsulating dedicated cargo proteins in vivo. They have been classified into four families based on sequence identity and operon structure, and thousands of encapsulin systems have recently been computationally identified across a wide range of bacterial and archaeal phyla. Cargo encapsulation is mediated by the presence of specific targeting motifs found in all native cargo proteins that interact with the interior surface of the encapsulin shell during self-assembly. Short C-terminal targeting peptides (TPs) are well documented in Family 1 encapsulins, while more recently, larger N-terminal targeting domains (TDs) have been discovered in Family 2. The modular nature of TPs and their facile genetic fusion to non-native cargo proteins of interest has made cargo encapsulation, both in vivo and in vitro, readily exploitable and has therefore resulted in a range of rationally engineered nano-compartmentalization systems. This review summarizes current knowledge on cargo protein encapsulation within encapsulins and highlights select studies that utilize TP fusions to non-native cargo in creative and useful ways.
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Affiliation(s)
- Jesse A Jones
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, USA.
| | - Robert Benisch
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
| | - Tobias W Giessen
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, USA.
- Program in Chemical Biology, University of Michigan, Ann Arbor, MI, USA
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2
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Podgorski JM, Freeman K, Gosselin S, Huet A, Conway JF, Bird M, Grecco J, Patel S, Jacobs-Sera D, Hatfull G, Gogarten JP, Ravantti J, White SJ. A structural dendrogram of the actinobacteriophage major capsid proteins provides important structural insights into the evolution of capsid stability. Structure 2023; 31:282-294.e5. [PMID: 36649709 PMCID: PMC10071307 DOI: 10.1016/j.str.2022.12.012] [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: 09/13/2022] [Revised: 10/31/2022] [Accepted: 12/19/2022] [Indexed: 01/19/2023]
Abstract
Many double-stranded DNA viruses, including tailed bacteriophages (phages) and herpesviruses, use the HK97-fold in their major capsid protein to make the capsomers of the icosahedral viral capsid. After the genome packaging at near-crystalline densities, the capsid is subjected to a major expansion and stabilization step that allows it to withstand environmental stresses and internal high pressure. Several different mechanisms for stabilizing the capsid have been structurally characterized, but how these mechanisms have evolved is still not understood. Using cryo-EM structure determination of 10 capsids, structural comparisons, phylogenetic analyses, and Alphafold predictions, we have constructed a detailed structural dendrogram describing the evolution of capsid structural stability within the actinobacteriophages. We show that the actinobacteriophage major capsid proteins can be classified into 15 groups based upon their HK97-fold.
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Affiliation(s)
- Jennifer M Podgorski
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA
| | - Krista Freeman
- Clapp Hall, Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Sophia Gosselin
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA
| | - Alexis Huet
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - James F Conway
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Mary Bird
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA
| | - John Grecco
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA
| | - Shreya Patel
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA
| | - Deborah Jacobs-Sera
- Clapp Hall, Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Graham Hatfull
- Clapp Hall, Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Johann Peter Gogarten
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA; Institute for Systems Genomics, University of Connecticut, Storrs, CT 06268-3125, USA
| | - Janne Ravantti
- University of Helsinki, Molecular and Integrative Biosciences Research Programme, Helsinki, Finland
| | - Simon J White
- Biology/Physics Building, Department of Molecular and Cell Biology, University of Connecticut, 91 North Eagleville Road, Unit-3125, Storrs, CT 06269-3125, USA.
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3
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Davis CR, Backos D, Morais MC, Churchill MEA, Catalano CE. Characterization of a Primordial Major Capsid-Scaffolding Protein Complex in Icosahedral Virus Shell Assembly. J Mol Biol 2022; 434:167719. [PMID: 35820453 DOI: 10.1016/j.jmb.2022.167719] [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: 02/26/2022] [Revised: 06/07/2022] [Accepted: 07/06/2022] [Indexed: 12/15/2022]
Abstract
Capsid assembly pathways are strongly conserved in the complex dsDNA viruses, where major capsid proteins (MCP) self-assemble into icosahedral procapsid shells, chaperoned by a scaffolding protein. Without a scaffold, the capsid proteins aggregate and form aberrant structures. This, coupled with the rapid co-polymerization of MCP and scaffolding proteins, has thwarted characterization of the earliest steps in shell assembly. Here we interrogate the structure and biophysical properties of a soluble, assembly-deficient phage lambda major capsid protein, MCP(W308A). The mutant protein is folded, soluble to high concentrations and binds to the scaffolding protein in an apparent SP2:MCP(W308A)1 stoichiometry but does not assemble beyond this initiating complex. The MCP(W308A) crystal structure was solved to 2.7 Å revealing the canonical HK97 fold in a "pre-assembly" conformation featuring the conserved N-arm and E-loops folded into the body of the protein. Structural, biophysical and computational analyses suggest that MCP(W308A) is thermodynamically trapped in this pre-assembly conformation precluding self-association interactions required for shell assembly. A model is described wherein dynamic interactions between MCP proteins play an essential role in high fidelity viral shell assembly. Scaffold-chaperoned MCP polymerization is a strongly conserved process in all the large dsDNA viruses and our results provide insight into this primordial complex in solution and have broad biological significance in our understanding of virus assembly mechanisms.
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Affiliation(s)
- Christal R Davis
- Program in Structural Biology and Biochemistry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Donald Backos
- Department of Pharmaceutical Chemistry, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Marc C Morais
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - Mair E A Churchill
- Program in Structural Biology and Biochemistry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Carlos E Catalano
- Program in Structural Biology and Biochemistry, University of Colorado Anschutz Medical Campus, Aurora, CO, USA; Department of Pharmaceutical Chemistry, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
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4
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Jones JA, Cristie-David AS, Andreas MP, Giessen TW. Triggered Reversible Disassembly of an Engineered Protein Nanocage*. Angew Chem Int Ed Engl 2021; 60:25034-25041. [PMID: 34532937 PMCID: PMC8578439 DOI: 10.1002/anie.202110318] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Indexed: 01/13/2023]
Abstract
Protein nanocages play crucial roles in sub-cellular compartmentalization and spatial control in all domains of life and have been used as biomolecular tools for applications in biocatalysis, drug delivery, and bionanotechnology. The ability to control their assembly state under physiological conditions would further expand their practical utility. To gain such control, we introduced a peptide capable of triggering conformational change at a key structural position in the largest known encapsulin nanocompartment. We report the structure of the resulting engineered nanocage and demonstrate its ability to disassemble and reassemble on demand under physiological conditions. We demonstrate its capacity for in vivo encapsulation of proteins of choice while also demonstrating in vitro cargo loading capabilities. Our results represent a functionally robust addition to the nanocage toolbox and a novel approach for controlling protein nanocage disassembly and reassembly under mild conditions.
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Affiliation(s)
- Jesse A Jones
- Department of Biomedical Engineering, University of Michigan Medical School, Ann Arbor, 1150 W. Medical Center Dr., MSRB2, Ann Arbor, MI, 48109-5622, USA
| | - Ajitha S Cristie-David
- Department of Biomedical Engineering, University of Michigan Medical School, Ann Arbor, 1150 W. Medical Center Dr., MSRB2, Ann Arbor, MI, 48109-5622, USA
| | - Michael P Andreas
- Department of Biomedical Engineering, University of Michigan Medical School, Ann Arbor, 1150 W. Medical Center Dr., MSRB2, Ann Arbor, MI, 48109-5622, USA
| | - Tobias W Giessen
- Department of Biomedical Engineering, University of Michigan Medical School, Ann Arbor, 1150 W. Medical Center Dr., MSRB2, Ann Arbor, MI, 48109-5622, USA
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, 1150 W. Medical Center Dr., MSRB2, Ann Arbor, MI, 48109-5622, USA
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5
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Jones JA, Cristie‐David AS, Andreas MP, Giessen TW. Triggered Reversible Disassembly of an Engineered Protein Nanocage**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202110318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Jesse A. Jones
- Department of Biomedical Engineering University of Michigan Medical School, Ann Arbor 1150 W. Medical Center Dr., MSRB2 Ann Arbor MI 48109-5622 USA
| | - Ajitha S. Cristie‐David
- Department of Biomedical Engineering University of Michigan Medical School, Ann Arbor 1150 W. Medical Center Dr., MSRB2 Ann Arbor MI 48109-5622 USA
| | - Michael P. Andreas
- Department of Biomedical Engineering University of Michigan Medical School, Ann Arbor 1150 W. Medical Center Dr., MSRB2 Ann Arbor MI 48109-5622 USA
| | - Tobias W. Giessen
- Department of Biomedical Engineering University of Michigan Medical School, Ann Arbor 1150 W. Medical Center Dr., MSRB2 Ann Arbor MI 48109-5622 USA
- Department of Biological Chemistry University of Michigan Medical School, Ann Arbor 1150 W. Medical Center Dr., MSRB2 Ann Arbor MI 48109-5622 USA
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6
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Jones JA, Giessen TW. Advances in encapsulin nanocompartment biology and engineering. Biotechnol Bioeng 2020; 118:491-505. [PMID: 32918485 DOI: 10.1002/bit.27564] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/12/2020] [Accepted: 09/09/2020] [Indexed: 12/23/2022]
Abstract
Compartmentalization is an essential feature of all cells. It allows cells to segregate and coordinate physiological functions in a controlled and ordered manner. Different mechanisms of compartmentalization exist, with the most relevant to prokaryotes being encapsulation via self-assembling protein-based compartments. One widespread example of such is that of encapsulins-cage-like protein nanocompartments able to compartmentalize specific reactions, pathways, and processes in bacteria and archaea. While still relatively nascent bioengineering tools, encapsulins exhibit many promising characteristics, including a number of defined compartment sizes ranging from 24 to 42 nm, straightforward expression, the ability to self-assemble via the Hong Kong 97-like fold, marked physical robustness, and internal and external handles primed for rational genetic and molecular manipulation. Moreover, encapsulins allow for facile and specific encapsulation of native or heterologous cargo proteins via naturally or rationally fused targeting peptide sequences. Taken together, the attributes of encapsulins promise substantial customizability and broad usability. This review discusses recent advances in employing engineered encapsulins across various fields, from their use as bionanoreactors to targeted delivery systems and beyond. A special focus will be provided on the rational engineering of encapsulin systems and their potential promise as biomolecular research tools.
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Affiliation(s)
- Jesse A Jones
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Tobias W Giessen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.,Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, USA
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7
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Maurer JB, Oh B, Moyer CL, Duda RL. Capsids and Portals Influence Each Other's Conformation During Assembly and Maturation. J Mol Biol 2020; 432:2015-2029. [PMID: 32035900 DOI: 10.1016/j.jmb.2020.01.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/04/2020] [Accepted: 01/14/2020] [Indexed: 01/22/2023]
Abstract
The portal proteins of tailed bacteriophage and Herpesvirus capsids form dodecameric rings that occupy one capsid vertex and are incorporated during the assembly of capsid precursors called procapsids or proheads. Portals are essential and serve as the pore for DNA transit and the site of tail attachment; however, bacteriophage HK97 capsid proteins assemble efficiently without a portal when expressed from plasmids. Following portal co-expression, portals were incorporated into about half of the proheads that were made. In the absence of active capsid maturation protease, uncleaved proheads formed dimers, trimers, and tetramers of proheads during purification, but only if they had portals. These appeared bound to membrane-like fragments by their portals and could be disaggregated by detergents, supporting a role for membranes in their formation and in capsid assembly. The precursors to prohead oligomers were detected in cell extracts. These were able to bind to Octyl-Sepharose and could be released by detergent, while uncleaved proheads without portal or cleaved proheads with portal did not bind. Our results document a discrete change in the HK97 portal's hydrophobicity induced by cleavage of the procapsid shell in which it is embedded. Additionally, we detected an increase in the rate of expansion induced by the presence of a portal complex in cleaved HK97 proheads. These results suggest that portals and capsids influence each other's conformation during assembly. The formation of prohead oligomers also provides a rapid and sensitive assay for identification and analysis of portal incorporation mutants.
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Affiliation(s)
- Joshua B Maurer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Bonnie Oh
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Crystal L Moyer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Robert L Duda
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA.
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8
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Capsid expansion of bacteriophage T5 revealed by high resolution cryoelectron microscopy. Proc Natl Acad Sci U S A 2019; 116:21037-21046. [PMID: 31578255 DOI: 10.1073/pnas.1909645116] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The large (90-nm) icosahedral capsid of bacteriophage T5 is composed of 775 copies of the major capsid protein (mcp) together with portal, protease, and decoration proteins. Its assembly is a regulated process that involves several intermediates, including a thick-walled round precursor prohead that expands as the viral DNA is packaged to yield a thin-walled and angular mature capsid. We investigated capsid maturation by comparing cryoelectron microscopy (cryo-EM) structures of the prohead, the empty expanded capsid both with and without decoration protein, and the virion capsid at a resolution of 3.8 Å for the latter. We detail the molecular structure of the mcp, its complex pattern of interactions, and their evolution during maturation. The bacteriophage T5 mcp is a variant of the canonical HK97-fold with a high level of plasticity that allows for the precise assembly of a giant macromolecule and the adaptability needed to interact with other proteins and the packaged DNA.
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9
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Asija K, Teschke CM. Of capsid structure and stability: The partnership between charged residues of E-loop and P-domain of the bacteriophage P22 coat protein. Virology 2019; 534:45-53. [PMID: 31176063 PMCID: PMC6614003 DOI: 10.1016/j.virol.2019.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 05/27/2019] [Accepted: 05/31/2019] [Indexed: 01/14/2023]
Abstract
Tailed dsDNA bacteriophages and herpesviruses form capsids using coat proteins that have the HK97 fold. In these viruses, the coat proteins first assemble into procapsids, which subsequently mature during DNA packaging. Generally interactions between the coat protein E-loop of one subunit and the P-domain of an adjacent subunit help stabilize both capsomers and capsids. Based on a recent 3.3 Å cryo-EM structure of the bacteriophage P22 virion, E-loop amino acids E52, E59 and E72 were suggested to stabilize the capsid through intra-capsomer salt bridges with the P-domain residues R102, R109 and K118. The glutamic acid residues were each mutated to alanine to test this hypothesis. The substitutions resulted in a WT phenotype and did not destabilize capsids; rather, the alanine substituted coat proteins increased the stability of procapsids and virions. These results indicate that different types of interactions must be used between the E-loop and P-domain to stabilize phage P22 procapsids and virions.
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Affiliation(s)
- Kunica Asija
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA; Department of Chemistry, University of Connecticut, Storrs, CT, USA.
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10
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Asija K, Teschke CM. A Hydrophobic Network: Intersubunit and Intercapsomer Interactions Stabilizing the Bacteriophage P22 Capsid. J Virol 2019; 93:e00727-19. [PMID: 31068429 PMCID: PMC6600197 DOI: 10.1128/jvi.00727-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 05/02/2019] [Indexed: 11/20/2022] Open
Abstract
Double-stranded DNA (dsDNA) tailed phages and herpesviruses assemble their capsids using coat proteins that have the ubiquitous HK97 fold. Though this fold is common, we do not have a thorough understanding of the different ways viruses adapt it to maintain stability in various environments. The HK97-fold E-loop, which connects adjacent subunits at the outer periphery of capsomers, has been implicated in capsid stability. Here, we show that in bacteriophage P22, residue W61 at the tip of the E-loop plays a role in stabilizing procapsids and in maturation. We hypothesize that a hydrophobic pocket is formed by residues I366 and W410 in the P domain of a neighboring subunit within a capsomer, into which W61 fits like a peg. In addition, W61 likely bridges to residues A91 and L401 in P-domain loops of an adjacent capsomer, thereby linking the entire capsid together with a network of hydrophobic interactions. There is conservation of this hydrophobic network in the distantly related P22-like phages, indicating that this structural feature is likely important for stabilizing this family of phages. Thus, our data shed light on one of the varied elegant mechanisms used in nature to consistently build stable viral genome containers through subtle adaptation of the HK97 fold.IMPORTANCE Similarities in assembly reactions and coat protein structures of the dsDNA tailed phages and herpesviruses make phages ideal models to understand capsid assembly and identify potential targets for antiviral drug discovery. The coat protein E-loops of these viruses are involved in both intra- and intercapsomer interactions. In phage P22, hydrophobic interactions peg the coat protein subunits together within a capsomer, where the E-loop hydrophobic residue W61 of one subunit packs into a pocket of hydrophobic residues I366 and W410 of the adjacent subunit. W61 also makes hydrophobic interactions with A91 and L401 of a subunit in an adjacent capsomer. We show these intra- and intercapsomer hydrophobic interactions form a network crucial to capsid stability and proper assembly.
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Affiliation(s)
- Kunica Asija
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, USA
- Department of Chemistry, University of Connecticut, Storrs, Connecticut, USA
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11
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Duda RL, Teschke CM. The amazing HK97 fold: versatile results of modest differences. Curr Opin Virol 2019; 36:9-16. [PMID: 30856581 PMCID: PMC6626583 DOI: 10.1016/j.coviro.2019.02.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/27/2019] [Accepted: 02/04/2019] [Indexed: 02/08/2023]
Abstract
dsDNA Bacteriophages, some dsDNA archaeal viruses and the Herpesviruses share many features including a common capsid assembly pathway and coat protein fold. The coat proteins of these viruses, which have the HK97 fold, co-assemble with a free or attached scaffolding protein and other capsid proteins into a precursor capsid, known as a procapsid or prohead. The procapsid is a metastable state that increases in stability as a result of morphological changes that occur during the dsDNA packaging reaction. We review evidence from several systems indicating that proper contacts acquired in the assembly of the procapsid are critical to forming the correct morphology in the mature capsid.
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Affiliation(s)
- Robert L Duda
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States.
| | - Carolyn M Teschke
- Departments of Molecular and Cell Biology, and Chemistry, University of Connecticut, Storrs, CT, 06269-3125, United States.
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12
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Flexible Connectors between Capsomer Subunits that Regulate Capsid Assembly. J Mol Biol 2017; 429:2474-2489. [PMID: 28705762 DOI: 10.1016/j.jmb.2017.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 06/25/2017] [Accepted: 07/06/2017] [Indexed: 01/28/2023]
Abstract
Viruses build icosahedral capsids of specific size and shape by regulating the spatial arrangement of the hexameric and pentameric protein capsomers in the growing shell during assembly. In the T=7 capsids of Escherichia coli bacteriophage HK97 and other phages, 60 capsomers are hexons, while the rest are pentons that are correctly positioned during assembly. Assembly of the HK97 capsid to the correct size and shape has been shown to depend on specific ionic contacts between capsomers. We now describe additional ionic interactions within capsomers that also regulate assembly. Each is between the long hairpin, the "E-loop," that extends from one subunit to the adjacent subunit within the same capsomer. Glutamate E153 on the E-loop and arginine R210 on the adjacent subunit's backbone alpha-helix form salt bridges in hexamers and pentamers. Mutations that disrupt these salt bridges were lethal for virus production, because the mutant proteins assembled into tubes or sheets instead of capsids. X-ray structures show that the E153-R210 links are flexible and maintained during maturation despite radical changes in capsomer shape. The E153-R210 links appear to form early in assembly to enable capsomers to make programmed changes in their shape during assembly. The links also prevent flattening of capsomers and premature maturation. Mutant phenotypes and modeling support an assembly model in which flexible E153-R210 links mediate capsomer shape changes that control where pentons are placed to create normal-sized capsids. The E-loop may be conserved in other systems in order to play similar roles in regulating assembly.
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13
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Tso D, Peebles CL, Maurer JB, Duda RL, Hendrix RW. On the catalytic mechanism of bacteriophage HK97 capsid crosslinking. Virology 2017; 506:84-91. [PMID: 28359902 DOI: 10.1016/j.virol.2017.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 03/22/2017] [Accepted: 03/23/2017] [Indexed: 10/19/2022]
Abstract
During maturation of the phage HK97 capsid, each of the 415 capsid subunits forms covalent bonds to neighboring subunits, stabilizing the capsid. Crosslinking is catalyzed not by a separate enzyme but by subunits of the assembled capsid in response to conformational rearrangements during maturation. This report investigates the catalytic mechanism. Earlier work established that the crosslinks are isopeptide (amide) bonds between side chains of a lysine on one subunit and an asparagine on another subunit, aided by a catalytic glutamate on a third subunit. The mature capsid structure suggests that the reaction may be facilitated by the arrival of a valine with the lysine to complete a hydrophobic pocket surrounding the glutamate, lysine and asparagine. We show that this valine has an essential role for efficient crosslinking, and that any of six other amino acids can successfully substitute for valine. Evidently none of the remaining 13 amino acids will work.
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Affiliation(s)
- DanJu Tso
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Craig L Peebles
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Joshua B Maurer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Robert L Duda
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Roger W Hendrix
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Giessen TW, Silver PA. Converting a Natural Protein Compartment into a Nanofactory for the Size-Constrained Synthesis of Antimicrobial Silver Nanoparticles. ACS Synth Biol 2016; 5:1497-1504. [PMID: 27276075 DOI: 10.1021/acssynbio.6b00117] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Engineered biological systems are used extensively for the production of high value and commodity organics. On the other hand, most inorganic nanomaterials are still synthesized via chemical routes. By engineering cellular compartments, functional nanoarchitectures can be produced under environmentally sustainable conditions. Encapsulins are a new class of microbial nanocompartments with promising applications in nanobiotechnology. Here, we engineer the Thermotoga maritima encapsulin EncTm to yield a designed compartment for the size-constrained synthesis of silver nanoparticles (Ag NPs). These Ag NPs exhibit uniform shape and size distributions as well as long-term stability. Ambient aqueous conditions can be used for Ag NP synthesis, while no reducing agents or solvents need to be added. The antimicrobial activity of the synthesized protein-coated or shell-free Ag NPs is superior to that of silver nitrate and citrate-capped Ag NPs. This study establishes encapsulins as an engineerable platform for the synthesis of biogenic functional nanomaterials.
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Affiliation(s)
- Tobias W. Giessen
- Department
of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, United States
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts 02115, United States
| | - Pamela A. Silver
- Department
of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, United States
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, Massachusetts 02115, United States
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15
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Extensive subunit contacts underpin herpesvirus capsid stability and interior-to-exterior allostery. Nat Struct Mol Biol 2016; 23:531-9. [PMID: 27111889 PMCID: PMC4899274 DOI: 10.1038/nsmb.3212] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 03/23/2016] [Indexed: 11/09/2022]
Abstract
The herpesvirus capsid is a complex protein assembly that includes hundreds of copies of four major subunits and lesser numbers of several minor proteins, all of which are essential for infectivity. Cryo-electron microscopy is uniquely suited for studying interactions that govern the assembly and function of such large functional complexes. Here we report two high-quality capsid structures, from human herpes simplex virus type 1 (HSV-1) and the animal pseudorabies virus (PRV), imaged inside intact virions at ~7-Å resolution. From these, we developed a complete model of subunit and domain organization and identified extensive networks of subunit contacts that underpin capsid stability and form a pathway that may signal the completion of DNA packaging from the capsid interior to outer surface, thereby initiating nuclear egress. Differences in the folding and orientation of subunit domains between herpesvirus capsids suggest that common elements have been modified for specific functions.
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Abstract
First discovered in bacteriophage HK97, biological chainmail is a highly stable system formed by concatenated protein rings. Each subunit of the ring contains the HK97-like fold, which is characterized by its submarine-like shape with a 5-stranded β sheet in the axial (A) domain, spine helix in the peripheral (P) domain, and an extended (E) loop. HK97 capsid consists of covalently-linked copies of just one HK97-like fold protein and represents the most effective strategy to form highly stable chainmail needed for dsDNA genome encapsidation. Recently, near-atomic resolution structures enabled by cryo electron microscopy (cryoEM) have revealed a range of other, more complex variants of this strategy for constructing dsDNA viruses. The first strategy, exemplified by P22-like phages, is the attachment of an insertional (I) domain to the core 5-stranded β sheet of the HK97-like fold. The atomic models of the Bordetella phage BPP-1 showcases an alternative topology of the classic HK97 topology of the HK97-like fold, as well as the second strategy for constructing stable capsids, where an auxiliary jellyroll protein dimer serves to cement the non-covalent chainmail formed by capsid protein subunits. The third strategy, found in lambda-like phages, uses auxiliary protein trimers to stabilize the underlying non-covalent chainmail near the 3-fold axis. Herpesviruses represent highly complex viruses that use a combination of these strategies, resulting in four-level hierarchical organization including a non-covalent chainmail formed by the HK97-like fold domain found in the floor region. A thorough understanding of these structures should help unlock the enigma of the emergence and evolution of dsDNA viruses and inform bioengineering efforts based on these viruses.
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Affiliation(s)
- Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA.,California NanoSystems Institute (CNSI), University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Joshua Chiou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA
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Suhanovsky MM, Teschke CM. Nature's favorite building block: Deciphering folding and capsid assembly of proteins with the HK97-fold. Virology 2015; 479-480:487-97. [PMID: 25864106 PMCID: PMC4424165 DOI: 10.1016/j.virol.2015.02.055] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 02/24/2015] [Accepted: 02/27/2015] [Indexed: 01/08/2023]
Abstract
For many (if not all) bacterial and archaeal tailed viruses and eukaryotic Herpesvirdae the HK97-fold serves as the major architectural element in icosahedral capsid formation while still enabling the conformational flexibility required during assembly and maturation. Auxiliary proteins or Δ-domains strictly control assembly of multiple, identical, HK97-like subunits into procapsids with specific icosahedral symmetries, rather than aberrant non-icosahedral structures. Procapsids are precursor structures that mature into capsids in a process involving release of auxiliary proteins (or cleavage of Δ-domains), dsDNA packaging, and conformational rearrangement of the HK97-like subunits. Some coat proteins built on the ubiquitous HK97-fold also have accessory domains or loops that impart specific functions, such as increased monomer, procapsid, or capsid stability. In this review, we analyze the numerous HK97-like coat protein structures that are emerging in the literature (over 40 at time of writing) by comparing their topology, additional domains, and their assembly and misassembly reactions.
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Affiliation(s)
- Margaret M Suhanovsky
- Department of Molecular and Cell Biology, University of Connecticut, 91N. Eagleville Rd. Storrs, CT 06269-3125, USA.
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, 91N. Eagleville Rd. Storrs, CT 06269-3125, USA; Department of Chemistry, University of Connecticut, 91N. Eagleville Rd. Storrs, CT 06269-3125, USA.
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Rizzo AA, Suhanovsky MM, Baker ML, Fraser LCR, Jones LM, Rempel DL, Gross ML, Chiu W, Alexandrescu AT, Teschke CM. Multiple functional roles of the accessory I-domain of bacteriophage P22 coat protein revealed by NMR structure and CryoEM modeling. Structure 2014; 22:830-41. [PMID: 24836025 PMCID: PMC4068711 DOI: 10.1016/j.str.2014.04.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 04/02/2014] [Accepted: 04/07/2014] [Indexed: 11/17/2022]
Abstract
Some capsid proteins built on the ubiquitous HK97-fold have accessory domains imparting specific functions. Bacteriophage P22 coat protein has a unique insertion domain (I-domain). Two prior I-domain models from subnanometer cryoelectron microscopy (cryoEM) reconstructions differed substantially. Therefore, the I-domain's nuclear magnetic resonance structure was determined and also used to improve cryoEM models of coat protein. The I-domain has an antiparallel six-stranded β-barrel fold, not previously observed in HK97-fold accessory domains. The D-loop, which is dynamic in the isolated I-domain and intact monomeric coat protein, forms stabilizing salt bridges between adjacent capsomers in procapsids. The S-loop is important for capsid size determination, likely through intrasubunit interactions. Ten of 18 coat protein temperature-sensitive-folding substitutions are in the I-domain, indicating its importance in folding and stability. Several are found on a positively charged face of the β-barrel that anchors the I-domain to a negatively charged surface of the coat protein HK97-core.
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Affiliation(s)
- Alessandro A Rizzo
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Margaret M Suhanovsky
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Matthew L Baker
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA
| | - LaTasha C R Fraser
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Lisa M Jones
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Don L Rempel
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Michael L Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Wah Chiu
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA
| | - Andrei T Alexandrescu
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA.
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA; Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA.
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