Everything about Capsid totally explained
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A
capsid is the protein shell of a
virus. It consists of several
oligomeric subunits made of
protein. The capsid encloses the
genetic material of the virus.
Capsids are broadly classified according to their structure. The majority of viruses have capsids with either
helical or
icosahedral structure. Some viruses, such as
bacteriophages, have developed more complicated structures. The icosahedral shape, which has 20 equilateral triangular faces, approximates a
sphere, while the helical shape is cylindrical. 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.
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; some examples would include the inner nuclear membrane, the
golgi membrane, or the cell's outer
membrane.
Once the virus has infected the cell, it'll start replicating itself, using the mechanisms of the infected host cell. During this process, new capsid subunits are synthesized according to the genetic material of the virus, using the
protein biosynthesis mechanism of the cell. During the assembly process, a
portal subunit is assembled at one vertex of the capsid. Through this portal, viral
DNA or
RNA is transported into the capsid. The structure and assembly of the
Herpes virus Capsid Portal Protein has been imaged via
cryo-electron microscopy.
Structural analyses of major capsid protein (MCP) architectures have been used to categorise viruses into families. For example, the bacteriophage PRD1, Paramecium bursaria Chlorella algal virus, and mammalian adenovirus have been placed in the same family.
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