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Essus VA, Souza Júnior GSE, Nunes GHP, Oliveira JDS, de Faria BM, Romão LF, Cortines JR. Bacteriophage P22 Capsid as a Pluripotent Nanotechnology Tool. Viruses 2023; 15:516. [PMID: 36851730 PMCID: PMC9962691 DOI: 10.3390/v15020516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 02/15/2023] Open
Abstract
The Salmonella enterica bacteriophage P22 is one of the most promising models for the development of virus-like particle (VLP) nanocages. It possesses an icosahedral T = 7 capsid, assembled by the combination of two structural proteins: the coat protein (gp5) and the scaffold protein (gp8). The P22 capsid has the remarkable capability of undergoing structural transition into three morphologies with differing diameters and wall-pore sizes. These varied morphologies can be explored for the design of nanoplatforms, such as for the development of cargo internalization strategies. The capsid proteic nature allows for the extensive modification of its structure, enabling the addition of non-native structures to alter the VLP properties or confer them to diverse ends. Various molecules were added to the P22 VLP through genetic, chemical, and other means to both the capsid and the scaffold protein, permitting the encapsulation or the presentation of cargo. This allows the particle to be exploited for numerous purposes-for example, as a nanocarrier, nanoreactor, and vaccine model, among other applications. Therefore, the present review intends to give an overview of the literature on this amazing particle.
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Affiliation(s)
- Victor Alejandro Essus
- Laboratório de Virologia e Espectrometria de Massas (LAVEM), Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21590-902, Brazil
| | - Getúlio Silva e Souza Júnior
- Laboratório de Virologia e Espectrometria de Massas (LAVEM), Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21590-902, Brazil
| | - Gabriel Henrique Pereira Nunes
- Laboratório de Virologia e Espectrometria de Massas (LAVEM), Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21590-902, Brazil
| | - Juliana dos Santos Oliveira
- Laboratório de Virologia e Espectrometria de Massas (LAVEM), Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21590-902, Brazil
| | - Bruna Mafra de Faria
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bl. F026, Rio de Janeiro 21941-590, Brazil
| | - Luciana Ferreira Romão
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bl. F026, Rio de Janeiro 21941-590, Brazil
| | - Juliana Reis Cortines
- Laboratório de Virologia e Espectrometria de Massas (LAVEM), Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21590-902, Brazil
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Whitehead RD, Teschke CM, Alexandrescu AT. NMR Mapping of Disordered Segments from a Viral Scaffolding Protein Enclosed in a 23 MDa Procapsid. Biophys J 2019; 117:1387-1392. [PMID: 31585705 DOI: 10.1016/j.bpj.2019.08.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/27/2019] [Accepted: 08/30/2019] [Indexed: 01/10/2023] Open
Abstract
Scaffolding proteins (SPs) are required for the capsid shell assembly of many tailed double-stranded DNA bacteriophages, some archaeal viruses, herpesviruses, and adenoviruses. Despite their importance, only one high-resolution structure is available for SPs within procapsids. Here, we use the inherent size limit of NMR to identify mobile segments of the 303-residue phage P22 SP free in solution and when incorporated into a ∼23 MDa procapsid complex. Free SP gives NMR signals from its acidic N-terminus (residues 1-40) and basic C-terminus (residues 264-303), whereas NMR signals from the middle segment (residues 41-263) are missing because of intermediate conformational exchange on the NMR chemical shift timescale. When SP is incorporated into P22 procapsids, NMR signals from the C-terminal helix-turn-helix domain disappear because of binding to the procapsid interior. Signals from the N-terminal domain persist, indicating that this segment retains flexibility when bound to procapsids. The unstructured character of the N-terminus, coupled with its high content of negative charges, is likely important for dissociation and release of SP during the double-stranded DNA genome packaging step accompanying phage maturation.
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Affiliation(s)
- Richard D Whitehead
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut; Department of Chemistry, University of Connecticut, Storrs, Connecticut.
| | - Andrei T Alexandrescu
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut.
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McCoy K, Selivanovitch E, Luque D, Lee B, Edwards E, Castón JR, Douglas T. Cargo Retention inside P22 Virus-Like Particles. Biomacromolecules 2018; 19:3738-3746. [PMID: 30092631 DOI: 10.1021/acs.biomac.8b00867] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Viral protein cages, with their regular and programmable architectures, are excellent platforms for the development of functional nanomaterials. The ability to transform a virus into a material with intended structure and function relies on the existence of a well-understood model system, a noninfectious virus-like particle (VLP) counterpart. Here, we study the factors important to the ability of P22 VLP to retain or release various protein cargo molecules depending on the nature of the cargo, the capsid morphology, and the environmental conditions. Because the interaction between the internalized scaffold protein (SP) and the capsid coat protein (CP) is noncovalent, we have studied the efficiency with which a range of SP variants can dissociate from the interior of different P22 VLP morphologies and exit by traversing the porous capsid. Understanding the types of cargos that are either retained or released from the P22 VLP will aid in the rational design of functional nanomaterials.
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Affiliation(s)
- Kimberly McCoy
- Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405 , United States
| | - Ekaterina Selivanovitch
- Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405 , United States
| | - Daniel Luque
- Department of Structure of Macromolecules , Centro Nacional de Biotecnología (CNB-CSIC) , Darwin 3 , 28049 Madrid , Spain.,Centro Nacional de Microbiología/ISCIII, 28220 Majadahonda, Madrid , Spain
| | - Byeongdu Lee
- X-ray Science Division, Advanced Photon Source , Argonne National Laboratory , 9700 South Cass Avenue , Argonne , Illinois 60439 , United States
| | - Ethan Edwards
- Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405 , United States
| | - José R Castón
- Department of Structure of Macromolecules , Centro Nacional de Biotecnología (CNB-CSIC) , Darwin 3 , 28049 Madrid , Spain
| | - Trevor Douglas
- Department of Chemistry , Indiana University , 800 East Kirkwood Avenue , Bloomington , Indiana 47405 , United States
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Portal protein functions akin to a DNA-sensor that couples genome-packaging to icosahedral capsid maturation. Nat Commun 2017; 8:14310. [PMID: 28134243 PMCID: PMC5290284 DOI: 10.1038/ncomms14310] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/14/2016] [Indexed: 11/24/2022] Open
Abstract
Tailed bacteriophages and herpesviruses assemble infectious particles via an empty precursor capsid (or ‘procapsid') built by multiple copies of coat and scaffolding protein and by one dodecameric portal protein. Genome packaging triggers rearrangement of the coat protein and release of scaffolding protein, resulting in dramatic procapsid lattice expansion. Here, we provide structural evidence that the portal protein of the bacteriophage P22 exists in two distinct dodecameric conformations: an asymmetric assembly in the procapsid (PC-portal) that is competent for high affinity binding to the large terminase packaging protein, and a symmetric ring in the mature virion (MV-portal) that has negligible affinity for the packaging motor. Modelling studies indicate the structure of PC-portal is incompatible with DNA coaxially spooled around the portal vertex, suggesting that newly packaged DNA triggers the switch from PC- to MV-conformation. Thus, we propose the signal for termination of ‘Headful Packaging' is a DNA-dependent symmetrization of portal protein. Tailed bacteriophages assemble empty precursor capsids known as procapsids that are subsequently filled with viral DNA by a genome-packaging motor. Here the authors present a structure-based analysis that suggests the signal for termination of genome packaging is achieved through a DNA-dependent symmetrization of portal protein.
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Harprecht C, Okifo O, Robbins KJ, Motwani T, Alexandrescu AT, Teschke CM. Contextual Role of a Salt Bridge in the Phage P22 Coat Protein I-Domain. J Biol Chem 2016; 291:11359-72. [PMID: 27006399 DOI: 10.1074/jbc.m116.716910] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Indexed: 12/30/2022] Open
Abstract
The I-domain is a genetic insertion in the phage P22 coat protein that chaperones its folding and stability. Of 11 acidic residues in the I-domain, seven participate in stabilizing electrostatic interactions with basic residues across elements of secondary structure, fastening the β-barrel fold. A hydrogen-bonded salt bridge between Asp-302 and His-305 is particularly interesting as Asp-302 is the site of a temperature-sensitive-folding mutation. The pKa of His-305 is raised to 9.0, indicating the salt bridge stabilizes the I-domain by ∼4 kcal/mol. Consistently, urea denaturation experiments indicate the stability of the WT I-domain decreases by 4 kcal/mol between neutral and basic pH. The mutants D302A and H305A remove the pH dependence of stability. The D302A substitution destabilizes the I-domain by 4 kcal/mol, whereas H305A had smaller effects, on the order of 1-2 kcal/mol. The destabilizing effects of D302A are perpetuated in the full-length coat protein as shown by a higher sensitivity to protease digestion, decreased procapsid assembly rates, and impaired phage production in vivo By contrast, the mutants have only minor effects on capsid expansion or stability in vitro The effects of the Asp-302-His-305 salt bridge are thus complex and context-dependent. Substitutions that abolish the salt bridge destabilize coat protein monomers and impair capsid self-assembly, but once capsids are formed the effects of the substitutions are overcome by new quaternary interactions between subunits.
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Affiliation(s)
- Christina Harprecht
- From the Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Oghenefejiro Okifo
- From the Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Kevin J Robbins
- From the Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Tina Motwani
- From the Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Andrei T Alexandrescu
- From the Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
| | - Carolyn M Teschke
- From the Department of Molecular and Cell Biology and Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269
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6
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A Molecular Staple: D-Loops in the I Domain of Bacteriophage P22 Coat Protein Make Important Intercapsomer Contacts Required for Procapsid Assembly. J Virol 2015; 89:10569-79. [PMID: 26269173 DOI: 10.1128/jvi.01629-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 08/08/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Bacteriophage P22, a double-stranded DNA (dsDNA) virus, has a nonconserved 124-amino-acid accessory domain inserted into its coat protein, which has the canonical HK97 protein fold. This I domain is involved in virus capsid size determination and stability, as well as protein folding. The nuclear magnetic resonance (NMR) solution structure of the I domain revealed the presence of a D-loop, which was hypothesized to make important intersubunit contacts between coat proteins in adjacent capsomers. Here we show that amino acid substitutions of residues near the tip of the D-loop result in aberrant assembly products, including tubes and broken particles, highlighting the significance of the D-loops in proper procapsid assembly. Using disulfide cross-linking, we showed that the tips of the D-loops are positioned directly across from each other both in the procapsid and the mature virion, suggesting their importance in both states. Our results indicate that D-loop interactions act as "molecular staples" at the icosahedral 2-fold symmetry axis and significantly contribute to stabilizing the P22 capsid for DNA packaging. IMPORTANCE Many dsDNA viruses have morphogenic pathways utilizing an intermediate capsid, known as a procapsid. These procapsids are assembled from a coat protein having the HK97 fold in a reaction driven by scaffolding proteins or delta domains. Maturation of the capsid occurs during DNA packaging. Bacteriophage HK97 uniquely stabilizes its capsid during maturation by intercapsomer cross-linking, but most virus capsids are stabilized by alternate means. Here we show that the I domain that is inserted into the coat protein of bacteriophage P22 is important in the process of proper procapsid assembly. Specifically, the I domain allows for stabilizing interactions across the capsid 2-fold axis of symmetry via a D-loop. When amino acid residues at the tip of the D-loop are mutated, aberrant assembly products, including tubes, are formed instead of procapsids, consequently phage production is affected, indicating the importance of stabilizing interactions during the assembly and maturation reactions.
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Highly specific salt bridges govern bacteriophage P22 icosahedral capsid assembly: identification of the site in coat protein responsible for interaction with scaffolding protein. J Virol 2014; 88:5287-97. [PMID: 24600011 DOI: 10.1128/jvi.00036-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Icosahedral virus assembly requires a series of concerted and highly specific protein-protein interactions to produce a proper capsid. In bacteriophage P22, only coat protein (gp5) and scaffolding protein (gp8) are needed to assemble a procapsid-like particle, both in vivo and in vitro. In scaffolding protein's coat binding domain, residue R293 is required for procapsid assembly, while residue K296 is important but not essential. Here, we investigate the interaction of scaffolding protein with acidic residues in the N-arm of coat protein, since this interaction has been shown to be electrostatic. Through site-directed mutagenesis of genes 5 and 8, we show that changing coat protein N-arm residue 14 from aspartic acid to alanine causes a lethal phenotype. Coat protein residue D14 is shown by cross-linking to interact with scaffolding protein residue R293 and, thus, is intimately involved in proper procapsid assembly. To a lesser extent, coat protein N-arm residue E18 is also implicated in the interaction with scaffolding protein and is involved in capsid size determination, since a cysteine mutation at this site generated petite capsids. The final acidic residue in the N-arm that was tested, E15, is shown to only weakly interact with scaffolding protein's coat binding domain. This work supports growing evidence that surface charge density may be the driving force of virus capsid protein interactions. IMPORTANCE Bacteriophage P22 infects Salmonella enterica serovar Typhimurium and is a model for icosahedral viral capsid assembly. In this system, coat protein interacts with an internal scaffolding protein, triggering the assembly of an intermediate called a procapsid. Previously, we determined that there is a single amino acid in scaffolding protein required for P22 procapsid assembly, although others modulate affinity. Here, we identify partners in coat protein. We show experimentally that relatively weak interactions between coat and scaffolding proteins are capable of driving correctly shaped and sized procapsids and that the lack of these proper protein-protein interfaces leads to aberrant structures. The present work represents an important contribution supporting the hypothesis that virus capsid assembly is governed by seemingly simple interactions. The highly specific nature of the subunit interfaces suggests that these could be good targets for antivirals.
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Zhou Z, Bedwell GJ, Li R, Prevelige PE, Gupta A. Formation mechanism of chalcogenide nanocrystals confined inside genetically engineered virus-like particles. Sci Rep 2014; 4:3832. [PMID: 24452221 PMCID: PMC3899596 DOI: 10.1038/srep03832] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 12/27/2013] [Indexed: 01/01/2023] Open
Abstract
Engineered virus-like particles (VLP) are attractive for fabricating nanostructured materials for applications in diverse areas such as catalysis, drug delivery, biomedicine, composites, etc. Basic understanding of the interaction between the inorganic guest and biomolecular host is thus important for the controlled synthesis of inorganic nanoparticles inside VLP and rational assembly of ordered VLP-based hierarchical nanostructures. We have investigated in detail the formation mechanism and growth kinetics of semiconducting nanocrystals confined inside genetically engineered bacteriophage P22 VLP using semiconducting CdS as a prototypical example. The selective nucleation and growth of CdS at the engineered sites is found to be uniform during the early stage, followed by a more stochastic growth process. Furthermore, kinetic studies reveal that the presence of an engineered biotemplate helps in significantly retarding the reaction rate. These findings provide guidance for the controlled synthesis of a wide range of other inorganic materials confined inside VLP, and are of practical importance for the rational design of VLP-based hierarchical nanostuctures.
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Affiliation(s)
- Ziyou Zhou
- 1] Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487, United States [2] Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Gregory J Bedwell
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Rui Li
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Peter E Prevelige
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, United States
| | - Arunava Gupta
- 1] Center for Materials for Information Technology, University of Alabama, Tuscaloosa, Alabama 35487, United States [2] Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, Alabama 35487, United States
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O'Neil A, Prevelige PE, Basu G, Douglas T. Coconfinement of fluorescent proteins: spatially enforced communication of GFP and mCherry encapsulated within the P22 capsid. Biomacromolecules 2012; 13:3902-7. [PMID: 23121071 DOI: 10.1021/bm301347x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The precise architectures of viruses and virus-like particles are proving to be highly advantageous in synthetic materials applications. Not only can these nanocontainers be harnessed as active materials, but they can be exploited for examining the effects of in vivo "cell-like" crowding and confinement on the properties of the encapsulated cargo. Here we report the first example of intermolecular communication between two proteins coencapsulated within the capsid architecture of the bacteriophage P22. Using a genetically engineered three-protein fusion between the P22 scaffold protein, and the FRET pair, GFP, and a red fluorescent protein (mCherry), we were able to direct the encapsulation of the genetic fusion when coexpressed with P22 coat protein. These self-assembled P22 capsids are densely packaged, occupying more than 24% of the available volume, and the molecular design assures a 1:1 ratio of the interacting proteins. To probe the effect of crowding and confinement on the FRET communication in this nanoenvironment, we spaced the donor-acceptor pair with variable length flexible linkers and examined the effect on FRET inside the capsid compared to the same tethered FRET pairs free in solution. The P22 system is unique in that the capsid morphology can be altered, without losing the encapsulated cargo, resulting in a doubling of the capsid volume. Thus, we have additionally examined the encapsulated fusions at two different internal concentrations. Our results indicate that FRET is sensitive to the expansion of the capsid and encapsulation enforces significant intermolecular communication, increasing FRET by 5-fold. This P22 coencapsulation system is a promising platform for studying crowding, enforced proximity, and confinement effects on communication between active proteins.
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Affiliation(s)
- Alison O'Neil
- Department of Chemistry and Biochemistry, Center for BioInspired Nanomaterials, Montana State University, Bozeman, Montana 59717, United States
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Padilla-Meier GP, Gilcrease EB, Weigele PR, Cortines JR, Siegel M, Leavitt JC, Teschke CM, Casjens SR. Unraveling the role of the C-terminal helix turn helix of the coat-binding domain of bacteriophage P22 scaffolding protein. J Biol Chem 2012; 287:33766-80. [PMID: 22879595 DOI: 10.1074/jbc.m112.393132] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many viruses encode scaffolding and coat proteins that co-assemble to form procapsids, which are transient precursor structures leading to progeny virions. In bacteriophage P22, the association of scaffolding and coat proteins is mediated mainly by ionic interactions. The coat protein-binding domain of scaffolding protein is a helix turn helix structure near the C terminus with a high number of charged surface residues. Residues Arg-293 and Lys-296 are particularly important for coat protein binding. The two helices contact each other through hydrophobic side chains. In this study, substitution of the residues of the interface between the helices, and the residues in the β-turn, by aspartic acid was used examine the importance of the conformation of the domain in coat binding. These replacements strongly affected the ability of the scaffolding protein to interact with coat protein. The severity of the defect in the association of scaffolding protein to coat protein was dependent on location, with substitutions at residues in the turn and helix 2 causing the most significant effects. Substituting aspartic acid for hydrophobic interface residues dramatically perturbs the stability of the structure, but similar substitutions in the turn had much less effect on the integrity of this domain, as determined by circular dichroism. We propose that the binding of scaffolding protein to coat protein is dependent on angle of the β-turn and the orientation of the charged surface on helix 2. Surprisingly, formation of the highly complex procapsid structure depends on a relatively simple interaction.
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Affiliation(s)
- G Pauline Padilla-Meier
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
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Conformational switch-defective X174 internal scaffolding proteins kinetically trap assembly intermediates before procapsid formation. J Virol 2012; 86:9911-8. [PMID: 22761377 DOI: 10.1128/jvi.01120-12] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Conformational switching is an overarching paradigm in which to describe scaffolding protein-mediated virus assembly. However, rapid morphogenesis with small assembly subunits hinders the isolation of early morphogenetic intermediates in most model systems. Consequently, conformational switches are often defined by comparing the structures of virions, procapsids and aberrantly assembled particles. In contrast, X174 morphogenesis proceeds through at least three preprocapsid intermediates, which can be biochemically isolated. This affords a detailed analysis of early morphogenesis and internal scaffolding protein function. Amino acid substitutions were generated for the six C-terminal, aromatic amino acids that mediate most coat-internal scaffolding protein contacts. The biochemical characterization of mutant assembly pathways revealed two classes of molecular defects, protein binding and conformational switching, a novel phenotype. The conformational switch mutations kinetically trapped assembly intermediates before procapsid formation. Although mutations trapped different particles, they shared common second-site suppressors located in the viral coat protein. This suggests a fluid assembly pathway, one in which the scaffolding protein induces a single, coat protein conformational switch and not a series of sequential reactions. In this model, an incomplete or improper switch would kinetically trap intermediates.
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12
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Zlotnick A, Suhanovsky MM, Teschke CM. The energetic contributions of scaffolding and coat proteins to the assembly of bacteriophage procapsids. Virology 2012; 428:64-9. [PMID: 22520942 DOI: 10.1016/j.virol.2012.03.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 02/18/2012] [Accepted: 03/29/2012] [Indexed: 01/17/2023]
Abstract
In vitro assembly of bacteriophage P22 procapsids requires coat protein and sub-stoichiometric concentrations of the internal scaffolding protein. If there is no scaffolding protein, coat protein assembles aberrantly, but only at higher concentrations. Too much scaffolding protein results in partial procapsids. By treating the procapsid as a lattice that can bind and be stabilized by scaffolding protein we dissect procapsid assembly as a function of protein concentration and scaffolding/coat protein ratio. We observe that (i) the coat-coat association is weaker for procapsids than for aberrant polymer formation, (ii) scaffolding protein makes a small but sufficient contribution to stability to favor the procapsid form, and (iii) there are multiple classes of scaffolding protein binding sites. This approach should be applicable to other heterogeneous virus assembly reactions and will facilitate our ability to manipulate such in vitro reactions to probe assembly, and for development of nanoparticles.
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Affiliation(s)
- Adam Zlotnick
- Department of Molecular & Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA.
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13
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Abstract
We examine virus maturation of selected nonenveloped and enveloped single-stranded RNA viruses, retroviruses, bacteriophages, and herpesviruses. Processes associated with maturation in the RNA viruses range from subtle (nodaviruses and picornaviruses) to dramatic (tetraviruses and togaviruses). The elaborate assembly and maturation pathway of HIV is discussed in contrast to the less sophisticated but highly efficient processes associated with togaviruses. Bacteriophage assembly and maturation are discussed in general terms, with specific examples chosen for emphasis. Finally the herpesviruses are compared with bacteriophages. The data support divergent evolution of nodaviruses, picornaviruses, and tetraviruses from a common ancestor and divergent evolution of alphaviruses and flaviviruses from a common ancestor. Likewise, bacteriophages and herpesviruses almost certainly share a common ancestor in their evolution. Comparing all the viruses, we conclude that maturation is a convergent process that is required to solve conflicting requirements in biological dynamics and function.
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Affiliation(s)
- David Veesler
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
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14
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Cortines JR, Weigele PR, Gilcrease EB, Casjens SR, Teschke CM. Decoding bacteriophage P22 assembly: identification of two charged residues in scaffolding protein responsible for coat protein interaction. Virology 2011; 421:1-11. [PMID: 21974803 DOI: 10.1016/j.virol.2011.09.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Revised: 08/15/2011] [Accepted: 09/08/2011] [Indexed: 11/17/2022]
Abstract
Proper assembly of viruses must occur through specific interactions between capsid proteins. Many double-stranded DNA viruses and bacteriophages require internal scaffolding proteins to assemble their coat proteins into icosahedral capsids. The 303 amino acid bacteriophage P22 scaffolding protein is mostly helical, and its C-terminal helix-turn-helix (HTH) domain binds to the coat protein during virion assembly, directing the formation of an intermediate structure called the procapsid. The interaction between coat and scaffolding protein HTH domain is electrostatic, but the amino acids that form the protein-protein interface have yet to be described. In the present study, we used alanine scanning mutagenesis of charged surface residues of the C-terminal HTH domain of scaffolding protein. We have determined that P22 scaffolding protein residues R293 and K296 are crucial for binding to coat protein and that the neighboring charges are not essential but do modulate the affinity between the two proteins.
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Affiliation(s)
- Juliana R Cortines
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
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