The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell
“Giant” phages have genomes of >200 kbp, confined in correspondingly large capsids whose assembly and maturation are still poorly understood. Nevertheless, the first assembly product is likely to be, as in other tailed phages, a procapsid that subsequently matures and packages the DNA. The associ...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-08-01
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| Series: | Viruses |
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| Online Access: | https://www.mdpi.com/1999-4915/12/9/910 |
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| author | J. Bernard Heymann Bing Wang William W. Newcomb Weimin Wu Dennis C. Winkler Naiqian Cheng Erin R. Reilly Ru-Ching Hsia Julie A. Thomas Alasdair C. Steven |
| author_facet | J. Bernard Heymann Bing Wang William W. Newcomb Weimin Wu Dennis C. Winkler Naiqian Cheng Erin R. Reilly Ru-Ching Hsia Julie A. Thomas Alasdair C. Steven |
| author_sort | J. Bernard Heymann |
| collection | DOAJ |
| description | “Giant” phages have genomes of >200 kbp, confined in correspondingly large capsids whose assembly and maturation are still poorly understood. Nevertheless, the first assembly product is likely to be, as in other tailed phages, a procapsid that subsequently matures and packages the DNA. The associated transformations include the cleavage of many proteins by the phage-encoded protease, as well as the thinning and angularization of the capsid. We exploited an amber mutation in the viral protease gene of the <i>Salmonella</i> giant phage SPN3US, which leads to the accumulation of a population of capsids with distinctive properties. Cryo-electron micrographs reveal patterns of internal density different from those of the DNA-filled heads of virions, leading us to call them “mottled capsids”. Reconstructions show an outer shell with T = 27 symmetry, an embellishment of the HK97 prototype composed of the major capsid protein, gp75, which is similar to some other giant viruses. The mottled capsid has a T = 1 inner icosahedral shell that is a complex network of loosely connected densities composed mainly of the ejection proteins gp53 and gp54. Segmentation of this inner shell indicated that a number of densities (~12 per asymmetric unit) adopt a “twisted hook” conformation. Large patches of a proteinaceous tetragonal lattice with a 67 Å repeat were also present in the cell lysate. The unexpected nature of these novel inner shell and lattice structures poses questions as to their functions in virion assembly. |
| first_indexed | 2024-03-10T17:10:25Z |
| format | Article |
| id | doaj.art-aee88b338a3a43249a7e73bbcc099c23 |
| institution | Directory Open Access Journal |
| issn | 1999-4915 |
| language | English |
| last_indexed | 2024-03-10T17:10:25Z |
| publishDate | 2020-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Viruses |
| spelling | doaj.art-aee88b338a3a43249a7e73bbcc099c232023-11-20T10:40:51ZengMDPI AGViruses1999-49152020-08-0112991010.3390/v12090910The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal ShellJ. Bernard Heymann0Bing Wang1William W. Newcomb2Weimin Wu3Dennis C. Winkler4Naiqian Cheng5Erin R. Reilly6Ru-Ching Hsia7Julie A. Thomas8Alasdair C. Steven9Laboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USALaboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USALaboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USALaboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USALaboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USALaboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USAThomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY 14623, USAElectron Microscopy Core Imaging Facility, University of Maryland School of Dentistry, Baltimore, MD 21201, USAThomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY 14623, USALaboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USA“Giant” phages have genomes of >200 kbp, confined in correspondingly large capsids whose assembly and maturation are still poorly understood. Nevertheless, the first assembly product is likely to be, as in other tailed phages, a procapsid that subsequently matures and packages the DNA. The associated transformations include the cleavage of many proteins by the phage-encoded protease, as well as the thinning and angularization of the capsid. We exploited an amber mutation in the viral protease gene of the <i>Salmonella</i> giant phage SPN3US, which leads to the accumulation of a population of capsids with distinctive properties. Cryo-electron micrographs reveal patterns of internal density different from those of the DNA-filled heads of virions, leading us to call them “mottled capsids”. Reconstructions show an outer shell with T = 27 symmetry, an embellishment of the HK97 prototype composed of the major capsid protein, gp75, which is similar to some other giant viruses. The mottled capsid has a T = 1 inner icosahedral shell that is a complex network of loosely connected densities composed mainly of the ejection proteins gp53 and gp54. Segmentation of this inner shell indicated that a number of densities (~12 per asymmetric unit) adopt a “twisted hook” conformation. Large patches of a proteinaceous tetragonal lattice with a 67 Å repeat were also present in the cell lysate. The unexpected nature of these novel inner shell and lattice structures poses questions as to their functions in virion assembly.https://www.mdpi.com/1999-4915/12/9/910cryoEM (cryo-electron microscopy)bacteriophagevirussingle particle analysis3D reconstructionscaffold |
| spellingShingle | J. Bernard Heymann Bing Wang William W. Newcomb Weimin Wu Dennis C. Winkler Naiqian Cheng Erin R. Reilly Ru-Ching Hsia Julie A. Thomas Alasdair C. Steven The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell Viruses cryoEM (cryo-electron microscopy) bacteriophage virus single particle analysis 3D reconstruction scaffold |
| title | The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell |
| title_full | The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell |
| title_fullStr | The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell |
| title_full_unstemmed | The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell |
| title_short | The Mottled Capsid of the <i>Salmonella</i> Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell |
| title_sort | mottled capsid of the i salmonella i giant phage spn3us a likely maturation intermediate with a novel internal shell |
| topic | cryoEM (cryo-electron microscopy) bacteriophage virus single particle analysis 3D reconstruction scaffold |
| url | https://www.mdpi.com/1999-4915/12/9/910 |
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