The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell

Heymann, J. Bernard; Wang, Bing; Newcomb, William W.; Wu, Weimin; Winkler, Dennis C.; Cheng, Naiqian; Reilly, Erin R.; Hsia, Ru-Ching; Thomas, Julie A.; Steven, Alasdair C.

doi:10.3390/v12090910

Open AccessArticle

The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell

by

J. Bernard Heymann

^1,*

,

Bing Wang

^1,2,

William W. Newcomb

¹,

Weimin Wu

^1,3,

Dennis C. Winkler

^1,4

,

Naiqian Cheng

^1,†,

Erin R. Reilly

⁵,

Ru-Ching Hsia

⁶,

Julie A. Thomas

^5,*

and

Alasdair C. Steven

¹

Laboratory for Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USA

²

NYU Langone Health, CryoEM Core Facility, Division of Advanced Research Technologies, New York, NY 10016, USA

³

NCI, NIH, Frederick, MD 21701, USA

⁴

Advanced Imaging Core, NIDCD, NIH, Bethesda, MD 20892, USA

⁵

Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY 14623, USA

⁶

Electron Microscopy Core Imaging Facility, University of Maryland School of Dentistry, Baltimore, MD 21201, USA

^*

Authors to whom correspondence should be addressed.

^†

Deceased.

Viruses 2020, 12(9), 910; https://doi.org/10.3390/v12090910

Submission received: 20 July 2020 / Revised: 13 August 2020 / Accepted: 18 August 2020 / Published: 19 August 2020

(This article belongs to the Special Issue Giant or Jumbo Phages)

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Abstract

“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 Salmonella 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.

Keywords: cryoEM (cryo-electron microscopy); bacteriophage; virus; single particle analysis; 3D reconstruction; scaffold; ejection proteins

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MDPI and ACS Style

Heymann, J.B.; Wang, B.; Newcomb, W.W.; Wu, W.; Winkler, D.C.; Cheng, N.; Reilly, E.R.; Hsia, R.-C.; Thomas, J.A.; Steven, A.C. The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell. Viruses 2020, 12, 910. https://doi.org/10.3390/v12090910

AMA Style

Heymann JB, Wang B, Newcomb WW, Wu W, Winkler DC, Cheng N, Reilly ER, Hsia R-C, Thomas JA, Steven AC. The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell. Viruses. 2020; 12(9):910. https://doi.org/10.3390/v12090910

Chicago/Turabian Style

Heymann, J. Bernard, Bing Wang, William W. Newcomb, Weimin Wu, Dennis C. Winkler, Naiqian Cheng, Erin R. Reilly, Ru-Ching Hsia, Julie A. Thomas, and Alasdair C. Steven. 2020. "The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell" Viruses 12, no. 9: 910. https://doi.org/10.3390/v12090910

APA Style

Heymann, J. B., Wang, B., Newcomb, W. W., Wu, W., Winkler, D. C., Cheng, N., Reilly, E. R., Hsia, R.-C., Thomas, J. A., & Steven, A. C. (2020). The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell. Viruses, 12(9), 910. https://doi.org/10.3390/v12090910

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The Mottled Capsid of the Salmonella Giant Phage SPN3US, a Likely Maturation Intermediate with a Novel Internal Shell

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