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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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2
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Tu IF, Lin TL, Yang FL, Lee IM, Tu WL, Liao JH, Ko TP, Wu WJ, Jan JT, Ho MR, Chou CY, Wang AHJ, Wu CY, Wang JT, Huang KF, Wu SH. Structural and biological insights into Klebsiella pneumoniae surface polysaccharide degradation by a bacteriophage K1 lyase: implications for clinical use. J Biomed Sci 2022; 29:9. [PMID: 35130876 PMCID: PMC8822698 DOI: 10.1186/s12929-022-00792-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 01/24/2022] [Indexed: 11/18/2022] Open
Abstract
Background K1 capsular polysaccharide (CPS)-associated Klebsiella pneumoniae is the primary cause of pyogenic liver abscesses (PLA) in Asia. Patients with PLA often have serious complications, ultimately leading to a mortality of ~ 5%. This K1 CPS has been reported as a promising target for development of glycoconjugate vaccines against K. pneumoniae infection. The pyruvylation and O-acetylation modifications on the K1 CPS are essential to the immune response induced by the CPS. To date, however, obtaining the fragments of K1 CPS that contain the pyruvylation and O-acetylation for generating glycoconjugate vaccines still remains a challenge. Methods We analyzed the digested CPS products with NMR spectroscopy and mass spectrometry to reveal a bacteriophage-derived polysaccharide depolymerase specific to K1 CPS. The biochemical and biophysical properties of the enzyme were characterized and its crystal structures containing bound CPS products were determined. We also performed site-directed mutagenesis, enzyme kinetic analysis, phage absorption and infectivity studies, and treatment of the K. pneumoniae-infected mice with the wild-type and mutant enzymes. Results We found a bacteriophage-derived polysaccharide lyase that depolymerizes the K1 CPS into fragments of 1–3 repeating trisaccharide units with the retention of the pyruvylation and O-acetylation, and thus the important antigenic determinants of intact K1 CPS. We also determined the 1.46-Å-resolution, product-bound crystal structure of the enzyme, revealing two distinct carbohydrate-binding sites in a trimeric β-helix architecture, which provide the first direct evidence for a second, non-catalytic, carbohydrate-binding site in bacteriophage-derived polysaccharide depolymerases. We demonstrate the tight interaction between the pyruvate moiety of K1 CPS and the enzyme in this second carbohydrate-binding site to be crucial to CPS depolymerization of the enzyme as well as phage absorption and infectivity. We also demonstrate that the enzyme is capable of protecting mice from K1 K. pneumoniae infection, even against a high challenge dose. Conclusions Our results provide insights into how the enzyme recognizes and depolymerizes the K1 CPS, and demonstrate the potential use of the protein not only as a therapeutic agent against K. pneumoniae, but also as a tool to prepare structurally-defined oligosaccharides for the generation of glycoconjugate vaccines against infections caused by this organism. Supplementary Information The online version contains supplementary material available at 10.1186/s12929-022-00792-4.
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Affiliation(s)
- I-Fan Tu
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Tzu-Lung Lin
- Department of Microbiology, National Taiwan University Hospital, Taipei, 100, Taiwan
| | - Feng-Ling Yang
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - I-Ming Lee
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Wei-Lin Tu
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Jiahn-Haur Liao
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Tzu-Ping Ko
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Wen-Jin Wu
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Jia-Tsrong Jan
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Meng-Ru Ho
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Ching-Yi Chou
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Andrew H-J Wang
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan
| | - Chung-Yi Wu
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Jin-Town Wang
- Department of Microbiology, National Taiwan University Hospital, Taipei, 100, Taiwan
| | - Kai-Fa Huang
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan.
| | - Shih-Hsiung Wu
- Institute of Biological Chemistry, Academia Sinica, No. 128 Academia Road Section 2, Nan‑Kang, Taipei, 115, Taiwan. .,Department of Chemistry, National Taiwan University, Taipei, 106, Taiwan.
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Cui N, Yang F, Zhang JT, Sun H, Chen Y, Yu RC, Chen ZP, Jiang YL, Han SJ, Xu X, Li Q, Zhou CZ. Capsid Structure of Anabaena Cyanophage A-1(L). J Virol 2021; 95:e0135621. [PMID: 34549983 PMCID: PMC8610606 DOI: 10.1128/jvi.01356-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 09/19/2021] [Indexed: 01/09/2023] Open
Abstract
A-1(L) is a freshwater cyanophage with a contractile tail that specifically infects Anabaena sp. PCC 7120, one of the model strains for molecular studies of cyanobacteria. Although isolated for half a century, its structure remains unknown, which limits our understanding on the interplay between A-1(L) and its host. Here we report the 3.35 Å cryo-EM structure of A-1(L) capsid, representing the first near-atomic resolution structure of a phage capsid with a T number of 9. The major capsid gp4 proteins assemble into 91 capsomers, including 80 hexons: 20 at the center of the facet and 60 at the facet edge, in addition to 11 identical pentons. These capsomers further assemble into the icosahedral capsid, via gradually increasing curvatures. Different from the previously reported capsids of known-structure, A-1(L) adopts a noncovalent chainmail structure of capsid stabilized by two kinds of mortise-and-tenon inter-capsomer interactions: a three-layered interface at the pseudo 3-fold axis combined with the complementarity in shape and electrostatic potential around the 2-fold axis. This unique capsomer construction enables A-1(L) to possess a rigid capsid, which is solely composed of the major capsid proteins with an HK97 fold. IMPORTANCE Cyanobacteria are the most abundant photosynthetic bacteria, contributing significantly to the biomass production, O2 generation, and CO2 consumption on our planet. Their community structure and homeostasis in natural aquatic ecosystems are largely regulated by the corresponding cyanophages. In this study, we solved the structure of cyanophage A-1(L) capsid at near-atomic resolution and revealed a unique capsid construction. This capsid structure provides the molecular details for better understanding the assembly of A-1(L), and a structural platform for future investigation and application of A-1(L) in combination with its host Anabaena sp. PCC 7120. As the first isolated freshwater cyanophage that infects the genetically tractable model cyanobacterium, A-1(L) should become an ideal template for the genetic engineering and synthetic biology studies.
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Affiliation(s)
- Ning Cui
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Feng Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Jun-Tao Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Hui Sun
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Yu Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Rong-Cheng Yu
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Zhi-Peng Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Yong-Liang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Shu-Jing Han
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Xudong Xu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
| | - Qiong Li
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
| | - Cong-Zhao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
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4
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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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5
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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: 4] [Impact Index Per Article: 0.8] [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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6
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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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7
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Conservation and Divergence of the I-Domain Inserted into the Ubiquitous HK97 Coat Protein Fold in P22-Like Bacteriophages. J Virol 2019; 93:JVI.00007-19. [PMID: 30787158 DOI: 10.1128/jvi.00007-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 02/08/2019] [Indexed: 12/23/2022] Open
Abstract
Despite very low sequence homology, the major capsid proteins of double-stranded DNA (dsDNA) bacteriophages, some archaeal viruses, and the herpesviruses share a structural motif, the HK97 fold. Bacteriophage P22, a paradigm for this class of viruses, belongs to a phage gene cluster that contains three homology groups: P22-like, CUS-3-like, and Sf6-like. The coat protein of each phage has an inserted domain (I-domain) that is more conserved than the rest of the coat protein. In P22, loops in the I-domain are critical for stabilizing intra- and intersubunit contacts that guide proper capsid assembly. The nuclear magnetic resonance (NMR) structures of the P22, CUS-3, and Sf6 I-domains reveal that they are all six-stranded, anti-parallel β-barrels. Nevertheless, significant structural differences occur in loops connecting the β-strands, in surface electrostatics used to dock the I-domains with their respective coat protein core partners, and in sequence motifs displayed on the capsid surfaces. Our data highlight the structural diversity of I-domains that could lead to variations in capsid assembly mechanisms and capsid surfaces adapted for specific phage functions.IMPORTANCE Comparative studies of protein structures often provide insights into their evolution. The HK97 fold is a structural motif used to form the coat protein shells that encapsidate the genomes of many dsDNA phages and viruses. The structure and function of coat proteins based on the HK97 fold are often embellished by the incorporation of I-domains. In the present work we compare I-domains from three phages representative of highly divergent P22-like homology groups. While the three I-domains share a six-stranded β-barrel skeleton, there are differences (i) in structure elements at the periphery of the conserved fold, (ii) in the locations of disordered loops important in capsid assembly and conformational transitions, (iii) in surfaces charges, and (iv) in sequence motifs that are potential ligand-binding sites. These structural modifications on the rudimentary I-domain fold suggest that considerable structural adaptability was needed to fulfill the versatile range of functional requirements for distinct phages.
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8
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Newcomer RL, Schrad JR, Gilcrease EB, Casjens SR, Feig M, Teschke CM, Alexandrescu AT, Parent KN. The phage L capsid decoration protein has a novel OB-fold and an unusual capsid binding strategy. eLife 2019; 8:e45345. [PMID: 30945633 PMCID: PMC6449081 DOI: 10.7554/elife.45345] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 03/20/2019] [Indexed: 12/15/2022] Open
Abstract
The major coat proteins of dsDNA tailed phages (order Caudovirales) and herpesviruses form capsids by a mechanism that includes active packaging of the dsDNA genome into a precursor procapsid, followed by expansion and stabilization of the capsid. These viruses have evolved diverse strategies to fortify their capsids, such as non-covalent binding of auxiliary 'decoration' (Dec) proteins. The Dec protein from the P22-like phage L has a highly unusual binding strategy that distinguishes between nearly identical three-fold and quasi-three-fold sites of the icosahedral capsid. Cryo-electron microscopy and three-dimensional image reconstruction were employed to determine the structure of native phage L particles. NMR was used to determine the structure/dynamics of Dec in solution. The NMR structure and the cryo-EM density envelope were combined to build a model of the capsid-bound Dec trimer. Key regions that modulate the binding interface were verified by site-directed mutagenesis.
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Affiliation(s)
- Rebecca L Newcomer
- Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsUnited States
| | - Jason R Schrad
- Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingUnited States
| | - Eddie B Gilcrease
- Division of Microbiology and Immunology, Department of PathologyUniversity of Utah School of MedicineSalt Lake CityUnited States
| | - Sherwood R Casjens
- Division of Microbiology and Immunology, Department of PathologyUniversity of Utah School of MedicineSalt Lake CityUnited States
| | - Michael Feig
- Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingUnited States
| | - Carolyn M Teschke
- Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsUnited States
| | - Andrei T Alexandrescu
- Department of Molecular and Cell BiologyUniversity of ConnecticutStorrsUnited States
| | - Kristin N Parent
- Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingUnited States
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9
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Asija K, Teschke CM. Lessons from bacteriophages part 1: Deriving utility from protein structure, function, and evolution. PLoS Pathog 2018; 14:e1006971. [PMID: 29772002 PMCID: PMC5957328 DOI: 10.1371/journal.ppat.1006971] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
- Kunica Asija
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Carolyn M. Teschke
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, United States of America
- * E-mail:
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10
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Coat Protein Mutations That Alter the Flux of Morphogenetic Intermediates through the ϕX174 Early Assembly Pathway. J Virol 2017; 91:JVI.01384-17. [PMID: 28978706 DOI: 10.1128/jvi.01384-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 09/25/2017] [Indexed: 11/20/2022] Open
Abstract
Two scaffolding proteins orchestrate ϕX174 morphogenesis. The internal scaffolding protein B mediates the formation of pentameric assembly intermediates, whereas the external scaffolding protein D organizes 12 of these intermediates into procapsids. Aromatic amino acid side chains mediate most coat-internal scaffolding protein interactions. One residue in the internal scaffolding protein and three in the coat protein constitute the core of the B protein binding cleft. The three coat gene codons were randomized separately to ascertain the chemical requirements of the encoded amino acids and the morphogenetic consequences of mutation. The resulting mutants exhibited a wide range of recessive phenotypes, which could generally be explained within a structural context. Mutants with phenylalanine, tyrosine, and methionine substitutions were phenotypically indistinguishable from the wild type. However, tryptophan substitutions were detrimental at two sites. Charged residues were poorly tolerated, conferring extreme temperature-sensitive and lethal phenotypes. Eighteen lethal and conditional lethal mutants were genetically and biochemically characterized. The primary defect associated with the missense substitutions ranged from inefficient internal scaffolding protein B binding to faulty procapsid elongation reactions mediated by external scaffolding protein D. Elevating B protein concentrations above wild-type levels via exogenous, cloned-gene expression compensated for inefficient B protein binding, as did suppressing mutations within gene B. Similarly, elevating D protein concentrations above wild-type levels or compensatory mutations within gene D suppressed faulty elongation. Some of the parental mutations were pleiotropic, affecting multiple morphogenetic reactions. This progressively reduced the flux of intermediates through the pathway. Accordingly, multiple mechanisms, which may be unrelated, could restore viability.IMPORTANCE Genetic analyses have been instrumental in deciphering the temporal events of many biochemical pathways. However, pleiotropic effects can complicate analyses. Vis-à-vis virion morphogenesis, an improper protein-protein interaction within an early assembly intermediate can influence the efficiency of all subsequent reactions. Consequently, the flux of assembly intermediates cumulatively decreases as the pathway progresses. During morphogenesis, ϕX174 coat protein participates in at least four well-defined reactions, each one characterized by an interaction with a scaffolding or structural protein. In this study, genetic analyses, biochemical characterizations, and physiological assays, i.e., elevating the protein levels with which the coat protein interacts, were used to elucidate pleiotropic effects that may alter the flux of intermediates through a morphogenetic pathway.
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11
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Tripler TN, Teschke CM, Alexandrescu AT. NMR assignments for the insertion domain of bacteriophage Sf6 coat protein. BIOMOLECULAR NMR ASSIGNMENTS 2017; 11:35-38. [PMID: 27798771 PMCID: PMC5344723 DOI: 10.1007/s12104-016-9716-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/04/2016] [Indexed: 06/06/2023]
Abstract
The P22 bacteriophage group is a subgroup of the λ phage supercluster, comprised of the three major sequence types Sf6, P22, and CUS-3, based on their capsid proteins. Our goal is to investigate the extent to which structure-function relationships are conserved for the viral coat proteins and I-domains in this subgroup. Sf6 is a phage that infects the human pathogen Shigella flexneri. The coat protein of Sf6 assembles into a procapsid, which further undergoes maturation during DNA packaging into an infectious virion. The Sf6 coat protein contains a genetically inserted domain, termed the I-domain, similar to the ones present in the P22 and CUS-3 coat proteins. Based on the P22 example, I-domains play important functional roles in capsid assembly, stability, viability, and size-determination. Here we report the 1H, 15N, and 13C chemical shift assignments for the I-domain of the Sf6 phage coat protein. Chemical shift-based secondary structure prediction and hydrogen-bond patterns from a long-range HNCO experiment indicate that the Sf6 I-domain adopts a 6-stranded β-barrel fold like those of P22 and CUS-3 but with important differences, including the absence of the D-loop that is critical for capsid assembly and the addition of a novel disordered loop region.
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Affiliation(s)
- Therese N Tripler
- Department of Molecular and Cell Biology, University of Connecticut, 91 N. Eagleville Road, Storrs, CT, 06269-3125, USA
| | - Carolyn M Teschke
- Department of Molecular and Cell Biology, University of Connecticut, 91 N. Eagleville Road, Storrs, CT, 06269-3125, USA.
- Department of Chemistry, University of Connecticut, 55 N. Eagleville Rd., Storrs, CT, 06269-3060, USA.
| | - Andrei T Alexandrescu
- Department of Molecular and Cell Biology, University of Connecticut, 91 N. Eagleville Road, Storrs, CT, 06269-3125, USA.
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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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Localization of the Houdinisome (Ejection Proteins) inside the Bacteriophage P22 Virion by Bubblegram Imaging. mBio 2016; 7:mBio.01152-16. [PMID: 27507825 PMCID: PMC4992974 DOI: 10.1128/mbio.01152-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The P22 capsid is a T=7 icosahedrally symmetric protein shell with a portal protein dodecamer at one 5-fold vertex. Extending outwards from that vertex is a short tail, and putatively extending inwards is a 15-nm-long α-helical barrel formed by the C-terminal domains of portal protein subunits. In addition to the densely packed genome, the capsid contains three “ejection proteins” (E-proteins [gp7, gp16, and gp20]) destined to exit from the tightly sealed capsid during the process of DNA delivery into target cells. We estimated their copy numbers by quantitative SDS-PAGE as approximately 12 molecules per virion of gp16 and gp7 and 30 copies of gp20. To localize them, we used bubblegram imaging, an adaptation of cryo-electron microscopy in which gaseous bubbles induced in proteins by prolonged irradiation are used to map the proteins’ locations. We applied this technique to wild-type P22, a triple mutant lacking all three E-proteins, and three mutants each lacking one E-protein. We conclude that all three E-proteins are loosely clustered around the portal axis, in the region displaced radially inwards from the portal crown. The bubblegram data imply that approximately half of the α-helical barrel seen in the portal crystal structure is disordered in the mature virion, and parts of the disordered region present binding sites for E-proteins. Thus positioned, the E-proteins are strategically placed to pass down the shortened barrel and through the portal ring and the tail, as they exit from the capsid during an infection. While it has long been appreciated that capsids serve as delivery vehicles for viral genomes, there is now growing awareness that viruses also deliver proteins into their host cells. P22 has three such proteins (ejection proteins [E-proteins]), whose initial locations in the virion have remained unknown despite their copious amounts (total of 2.5 MDa). This study succeeded in localizing them by the novel technique of bubblegram imaging. The P22 E-proteins are seen to be distributed around the orifice of the portal barrel. Interestingly, this barrel, 15 nm long in a crystal structure, is only about half as long in situ: the remaining, disordered, portion appears to present binding sites for E-proteins. These observations document a spectacular example of a regulatory order-disorder transition in a supramolecular system and demonstrate the potential of bubblegram imaging to map the components of other viruses as well as cellular complexes.
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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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