Virus Structure


Viruses are infectious obligate intracellular parasites consisting of an RNA or DNA genome in a protective coat. Virus particles cannot increase in size but are assembled from pre‐formed components in susceptible host cells. The assembly of virus particles is achieved by the information contained within the components of the particle, a process driven by the rules of symmetry and by the most thermodynamically stable configuration. Once formed, virus particles vary in stability, some being very fragile while others are extremely stable, enabling some viruses to maintain the infectivity of their genome for extended periods of time outside a host cell, a feature required by viruses which are transmitted environmentally rather than directly from host to host. The outer surface of the virus particle must be able to interact with a suitable host cell to enable the process of infection to occur.

Key Concepts

  • Virus particles (virions) are assembled from pre‐formed components and do not grow or divide.
  • The virus coat protects the virus genome from degradation and helps maintain infectivity.
  • The assembly of virus particles is driven by the components making up the particle and is driven by symmetry and thermodynamics. In some cases, temporary “scaffolding proteins” are used to help direct the assembly of the particle into the mature form.
  • Virus particles must interact with the host cell to establish the process of infection.
  • Virus particles vary in stability, some being very fragile while others are very tough and able to persist in the environment for extended periods of time.

Keywords: capsid; icosahedral symmetry; helical symmetry; tailed bacteriophage; enveloped virus

Figure 1. Some viruses and their families: size and morphology. (a) Vaccinia virus (Poxviridae); (b) Rabies virus (Rhabdoviridae); (c) Mumps virus (Paramyxoviridae); (d) T‐even viruses (Myoviridae); (e) Coliphage λ (Siphoviridae); (f) Herpes simplex virus (Herpesviridae); (g) Human adenovirus 2 (Adenoviridae); (h) Human immunodeficiency virus (Retroviridae); (i) Influenza virus (Orthomyxoviridae); (j) Tobacco mosaic virus (Tobamovirus); (k) Simian virus 40 (Papovaviridae); (l) Rhinovirus (Picornaviridae); (m) Maize streak virus (Geminiviridae); (n) Coliphage φX174 (Microviridae); (o) Canine parvovirus (Parvoviridae).
Figure 2. (a) Icosahedral symmetry. (b) Helical symmetry. μ, subunits per helical turn; P, pitch of helix; p, axial rise per subunit.


Arslan D, Legendre M, Seltzer V, Abergel C and Claverie JM (2011) Distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae. Proceedings of the National Academy of Sciences USA 108 (42): 17486–17491.

Booth TF, Rabb MJ and Beniac DR (2013) How do filovirus filaments bend without breaking? Trends in Microbiology 21 (11): 583–593.

Butler PJG, Finch JL and Zimmern D (1977) Configuration of tobacco mosaic virus RNA during virus assembly. Nature 265: 217–219.

Caspar D and Klug A (1962) Physical principles in the construction of regular viruses. Cold Spring Harbor Symposium on Quantitative Biology 27: 1–24.

Dufrêne YF (2014) Atomic Force Microscopy in Microbiology: New Structural and Functional Insights into the Microbial Cell Surface. mBio 5 (4): e01363‐14. DOI: 10.1128/mBio.01363-14.

Engelman A and Cherepanov P (2012) The structural biology of HIV‐1: mechanistic and therapeutic insights. Nature Reviews Microbiology 10 (4): 279–290.

Fokine A and Rossmann MG (2014) Molecular architecture of tailed double‐stranded DNA phages. Bacteriophage 4 (1): e28281.

Grimes JM, Burroughs JN, Gouet P, et al. (1998) The atomic structure of the bluetongue virus core. Nature 395: 470–478.

Harrison SC, Olson A, Schutt CE, Winkler FK and Bricogne G (1978) Tomato stunt virus at 2.9 Å resolution. Nature 276: 368–373.

King AM, Adams MJ, Lefkowitz EJ and Carstens EB (eds) (2012) Virus Taxonomy: Classification and Nomenclature of Viruses: Ninth Report of the International Committee on Taxonomy of Viruses, vol. 9. Elsevier. ISBN: 0123846846.

Kühlbrand, W. (2014) Microscopy: Cryo‐EM enters a new era. eLife 3: e03678

Liljas L, Unge T, Jones A, et al. (1982) Structure of satellite Tobacco necrosis virus at 3 nm resolution. Journal of Molecular Biology 159: 93–108.

Liu DT and Day LA (1994) Pf1 virus structure: helical coat protein and DNA with paraxial phosphates. Science 265: 671–674.

Riesner D and Gross HJ (1985) Viroids. Annual Review of Biochemistry 54: 531–564.

Philippe N, Legendre M, Doutre G, et al. (2013) Pandoraviruses: amoeba viruses with genomes up to 2.5 Mb reaching that of parasitic eukaryotes. Science 341 (6143): 281–286.

Rossmann MG (2013) Structure of viruses: a short history. Quarterly Reviews of Biophysics 46 (02): 133–180.

Suzan‐Monti M, La Scola B and Raoult D (2006) Genomic and evolutionary aspects of Mimivirus. Virus Research 117 (1): 145–155.

Further Reading

Cann AJ (2011) Principles of Molecular Virology, 5th edn. London, UK: Academic Press.

Chiu W, Roger MB and Garcea RL (1997) Structural Biology of Viruses. New York, NY: Oxford University Press.

Knipe DM and Howley PM (2013) Fields Virology, 6th edn. Philadelphia, PA: Lippincott Williams and Wilkins.

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Cann, Alan J(Feb 2015) Virus Structure. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000439.pub2]