capsid

Examples of capsid in the following topics:

• Nature of the Virion

  • The core confers infectivity, and the capsid provides specificity to the virus.
  • Virion capsids are formed from identical protein subunits called capsomeres.
  • Complex viruses code for proteins that assist in the construction of their capsid.
  • The capsid and entire virus structure can be mechanically (physically) probed through atomic force microscopy.
  • Structure of a capsid and the organization of molecules that constitute it.

• Virus Classification

  • Viruses can also be classified by the design of their capsids .
  • Enveloped viruses have membranes surrounding capsids.
  • For example, the tobacco mosaic virus has a naked helical capsid .
  • The adenovirus has an icosahedral capsid .
  • The capsid of the (a) polio virus is naked icosahedral; (b) the Epstein-Barr virus capsid is enveloped icosahedral; (c) the mumps virus capsid is an enveloped helix; (d) the tobacco mosaic virus capsid is naked helical; and (e) the herpesvirus capsid is complex.

• General Morphology

  • A complete virus particle, known as a virion, consists of nucleic acid surrounded by a protective coat of protein called a capsid.
  • The capsid is made from proteins encoded by the viral genome and its shape serves as the basis for morphological distinction.
  • Virally coded protein subunits will self-assemble to form a capsid, in general requiring the presence of the virus genome.
  • Complex viruses code for proteins that assist in the construction of their capsid.
  • The capsid and entire virus structure can be mechanically (physically) probed through atomic force microscopy.

• Complex and Asymmetrical Virus Particles

  • While some have symmetrical shapes, viruses with asymmetrical structures are referred to as "complex. " These viruses possess a capsid that is neither purely helical nor purely icosahedral, and may possess extra structures such as protein tails or a complex outer walls.
  • Mimivirus is the largest characterized virus, with a capsid diameter of 400 nm.
  • The capsid appears hexagonal under an electron microscope, therefore the capsid is probably icosahedral.

• Virus Attachment and Genome Entry

  • Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface.
  • Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface.
  • However, given that bacterial cell walls are less thick than plant cell walls due to their much smaller size, some viruses have evolved mechanisms that inject their genome into the bacterial cell across the cell wall, while the viral capsid remains outside

• Attachment and Entry of Herpes Simplex

  • Herpes simplex virus attaches to a host's cells with viral envelope glycoproteins, which then allows entry of the viral capsid into the host cell.
  • Afterward, gB interaction with the gH/gL complex creates an entry pore for the viral capsid.
  • Following attachment, the viral envelope fuses with the host cell membrane and the viral capsid gains entry into the cell.

• Viral Morphology

  • Viruses of all shapes and sizes consist of a nucleic acid core, an outer protein coating or capsid, and sometimes an outer envelope.
  • A virion consists of a nucleic acid core, an outer protein coating or capsid, and sometimes an outer envelope made of protein and phospholipid membranes derived from the host cell.
  • The capsid is made up of protein subunits called capsomeres.
  • Enveloped viruses have membranes surrounding capsids.
  • Enveloped virions like HIV consist of nucleic acid and capsid proteins surrounded by a phospholipid bilayer envelope and its associated proteins.

• Antiviral Agents that Prevent Virus Uncoating or Release

  • Uncoating is the process of capsid disintegration, which leads to the release of the genomic material.
  • This step is performed by viral or host enzymes, or by capsid dissociation alone.
  • It is believed that such drugs prevent the virus from uncoating by blocking the proteins on the capsid responsible for uncoating, such as ion channel proteins.
  • The ion channel has an important role in disintegrating the viral capsid.
  • Neuraminidase is an enzyme on the capsid of influenza virus .

• Replication of Herpes Simplex Virus

  • The late proteins form the capsid and the receptors on the surface of the virus.
  • Packaging of the viral particles — including the genome, core and the capsid - occurs in the nucleus of the cell.
  • This then fuses with the outer nuclear membrane releasing a naked capsid into the cytoplasm.

• Plant DNA Viruses

  • They have elongated, geminate capsids with two incomplete T=1 icosahedra joined at the missing vertex .
  • The capsids range in size from 18-20 nm in diameter with a length of about 30 nm.
  • Virions of this family have a capsid and are non-enveloped.
  • The capsid is icosahedral with diameter of 18-20 nm.
  • Drawing of geminiviruses, characterized by elongated, geminate capsids with two incomplete T=1 icosahedra joined at the missing vertex.