Schematic of a cytomegalovirusIllustration of geometric model changing between two possible capsids. A similar change of size has been observed as the result of a single amino-acid mutation[1]
A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The proteins making up the capsid are called capsid proteins or viral coat proteins (VCP). The capsid and inner genome is called the nucleocapsid.
Capsids are broadly classified according to their structure. The majority of the viruses have capsids with either helical or icosahedral[2][3] structure. Some viruses, such as bacteriophages, have developed more complicated structures due to constraints of elasticity and electrostatics.[4] The icosahedral shape, which has 20 equilateral triangular faces, approximates a sphere, while the helical shape resembles the shape of a spring, taking the space of a cylinder but not being a cylinder itself.[5] The capsid faces may consist of one or more proteins. For example, the foot-and-mouth disease virus capsid has faces consisting of three proteins named VP1–3.[6]
Some viruses are enveloped, meaning that the capsid is coated with a lipid membrane known as the viral envelope. The envelope is acquired by the capsid from an intracellular membrane in the virus' host; examples include the inner nuclear membrane, the Golgi membrane, and the cell's outer membrane.[7]
Once the virus has infected a cell and begins replicating itself, new capsid subunits are synthesized using the protein biosynthesis mechanism of the cell. In some viruses, including those with helical capsids and especially those with RNA genomes, the capsid proteins co-assemble with their genomes. In other viruses, especially more complex viruses with double-stranded DNA genomes, the capsid proteins assemble into empty precursor procapsids that include a specialized portal structure at one vertex. Through this portal, viral DNA is translocated into the capsid.[8]
Structural analyses of major capsid protein (MCP) architectures have been used to categorise viruses into lineages. For example, the bacteriophage PRD1, the algal virus Paramecium bursaria Chlorella virus-1 (PBCV-1), mimivirus and the mammalian adenovirus have been placed in the same lineage, whereas tailed, double-stranded DNA bacteriophages (Caudovirales) and herpesvirus belong to a second lineage.[9][10][11][12]
^Asensio MA, Morella NM, Jakobson CM, Hartman EC, Glasgow JE, Sankaran B, et al. (September 2016). "A Selection for Assembly Reveals That a Single Amino Acid Mutant of the Bacteriophage MS2 Coat Protein Forms a Smaller Virus-like Particle". Nano Letters. 16 (9): 5944–50. Bibcode:2016NanoL..16.5944A. doi:10.1021/acs.nanolett.6b02948. OSTI 1532201. PMID 27549001. S2CID 16706951.
^Lidmar J, Mirny L, Nelson DR (November 2003). "Virus shapes and buckling transitions in spherical shells". Physical Review E. 68 (5 Pt 1): 051910. arXiv:cond-mat/0306741. Bibcode:2003PhRvE..68e1910L. doi:10.1103/PhysRevE.68.051910. PMID 14682823. S2CID 6023873.
^Vernizzi G, Olvera de la Cruz M (November 2007). "Faceting ionic shells into icosahedra via electrostatics". Proceedings of the National Academy of Sciences of the United States of America. 104 (47): 18382–6. Bibcode:2007PNAS..10418382V. doi:10.1073/pnas.0703431104. PMC 2141786. PMID 18003933.
^Vernizzi G, Sknepnek R, Olvera de la Cruz M (March 2011). "Platonic and Archimedean geometries in multicomponent elastic membranes". Proceedings of the National Academy of Sciences of the United States of America. 108 (11): 4292–6. Bibcode:2011PNAS..108.4292V. doi:10.1073/pnas.1012872108. PMC 3060260. PMID 21368184.
^Branden C, Tooze J (1991). Introduction to Protein Structure. New York: Garland. pp. 161–162. ISBN 978-0-8153-0270-4.
^"Virus Structure (web-books.com)". Archived from the original on 2021-02-07. Retrieved 2007-07-10.
^Alberts B, Bray D, Lewis J, Raff M, Roberts K, Watson JD (1994). Molecular Biology of the Cell (4th ed.). p. 280.
^Newcomb WW, Homa FL, Brown JC (August 2005). "Involvement of the portal at an early step in herpes simplex virus capsid assembly". Journal of Virology. 79 (16): 10540–6. doi:10.1128/JVI.79.16.10540-10546.2005. PMC 1182615. PMID 16051846.
^Krupovic M, Bamford DH (December 2008). "Virus evolution: how far does the double beta-barrel viral lineage extend?". Nature Reviews. Microbiology. 6 (12): 941–8. doi:10.1038/nrmicro2033. PMID 19008892. S2CID 31542714.
^Forterre P (March 2006). "Three RNA cells for ribosomal lineages and three DNA viruses to replicate their genomes: a hypothesis for the origin of cellular domain". Proceedings of the National Academy of Sciences of the United States of America. 103 (10): 3669–74. Bibcode:2006PNAS..103.3669F. doi:10.1073/pnas.0510333103. PMC 1450140. PMID 16505372.
^Khayat R, Tang L, Larson ET, Lawrence CM, Young M, Johnson JE (December 2005). "Structure of an archaeal virus capsid protein reveals a common ancestry to eukaryotic and bacterial viruses". Proceedings of the National Academy of Sciences of the United States of America. 102 (52): 18944–9. doi:10.1073/pnas.0506383102. PMC 1323162. PMID 16357204.
^Laurinmäki PA, Huiskonen JT, Bamford DH, Butcher SJ (December 2005). "Membrane proteins modulate the bilayer curvature in the bacterial virus Bam35". Structure. 13 (12): 1819–28. doi:10.1016/j.str.2005.08.020. PMID 16338410.
making up the capsid are called capsid proteins or viral coat proteins (VCP). The capsid and inner genome is called the nucleocapsid. Capsids are broadly...
directly target the viral capsid. These have also been termed "Capsid-targeting Antivirals", "Capsid Effectors", and "Capsid Assembly Modulators (CAMs)"...
protein cage called the capsid, which is wrapped in a lipid bilayer called the envelope. The envelope is joined to the capsid by means of a tegument....
or E protein is a protein in the envelope, which may be acquired by the capsid from an infected host cell. Numerous human pathogenic viruses in circulation...
of beta barrel. It is very common in viral proteins, particularly viral capsid proteins. Taken together, the jelly roll and Greek key structures comprise...
single-stranded RNA of positive polarity which is enclosed by an icosahedral capsid. As of 1999[update] the molecular basis for the causation of congenital...
a replication initiator protein, called NS1, and the protein the viral capsid is made of. The coding portion of the genome is flanked by telomeres at...
The P24 capsid protein is the most abundant HIV protein with each virus containing approximately 1,500 to 3,000 p24 molecules. It is the major structural...
non-enveloped, with icosahedral geometries. Capsid diameters vary widely, from 23 to 40 nm in diameter. The larger capsids (38–40 nm) exhibit T=3 symmetry and...
structure of the proteins by which the virus acts; (ii) a protein coat, the capsid, which surrounds and protects the genetic material; and in some cases (iii)...
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between HIV-1 viral capsid protein (p24) subunits in capsid hexamers, interfering with essential steps of viral replication, including capsid-mediated nuclear...
Closterotomus norvegicus (also known as the potato capsid) is a species of bugs belonging to the family Miridae, subfamily Mirinae. It can be found feeding...
Minor capsid protein VP2 and minor capsid protein VP3 are viral proteins that are components of the polyomavirus capsid. Polyomavirus capsids are composed...
the capsid and the envelope of the virus. The genetic material of a virus is stored within a viral protein structure called the capsid. The capsid is a...
encode the HK97 fold major capsid protein. The HK97 fold major capsid protein (HK97 MCP) is the primary component of the viral capsid, which stores the viral...
taxonomic synonym Capsidae. Species in the family may be referred to as capsid bugs or "mirid bugs". Common names include plant bugs, leaf bugs, and grass...
their capsid protein subunits) in order to study protein-protein interactions; a proxy for the capsids' properties and functions. The helical capsid structure...
180 subunits (T=3). The diameter of the capsid is between 27 and 40 nm. Like other caliciviruses, the capsid of the sapovirus has round intends on its...
subunit of the capsid, an outer covering of protein that protects the genetic material of a virus. Capsomeres self-assemble to form the capsid. Subunits called...
is packaged in a viral capsid of about 40-50 nanometers in diameter, which is icosahedral in shape (T=7 symmetry). The capsid is composed of 72 pentameric...
HHV Capsid Portal Protein, or HSV-1 UL-6 protein, is the protein which forms a cylindrical portal in the capsid of Herpes simplex virus (HSV-1). The protein...
small, positive-sense, single-stranded RNA viruses with a 30 nm icosahedral capsid. The viruses in this family can cause a range of diseases including the...
major capsid protein (MCP) that has the HK97 fold. Viruses in the realm also share a number of other characteristics involving the capsid and capsid assembly...
transiently exposed hydrophobic gamma peptide and the metastability of the viral capsid. FHV can be engineered in insect cell culture allowing for the tailored...
codes for two. The RNA is surrounded by a three-layered icosahedral protein capsid. Viral particles are up to 76.5 nm in diameter and are not enveloped. There...
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