What are pentamers and hexamers?
Pentamers of subunits are colored red, and hexamers of subunits are colored in shades of yellow and orange. In the 1950s, before any virus structures had been determined, Watson and Crick predicted that viruses are symmetrical assemblies of many small subunits.
What is a icosahedral virus?
Icosahedral. These viruses appear spherical in shape, but a closer look actually reveals they are icosahedral. The icosahedron is made up of equilateral triangles fused together in a spherical shape. This is the most optimal way of forming a closed shell using identical protein sub-units.
Which viruses have icosahedral symmetry?
Icosahedral symmetry is ubiquitous among spherical viruses (1). A classic example is the cowpea chlorotic mottle virus (CCMV), a well studied RNA virus with a shell composed of exactly 180 identical proteins (subunits) (2, 3).
What is capsid of virus?
Viral capsids are nanometre-sized containers that possess complex mechanical properties and whose main function is to encapsidate the viral genome in one host, to transport it and to subsequently release it inside another host cell.
What is an example of a helical virus?
In contrast, all helical animal viruses are enveloped. These include well-known viruses such as influenza virus, measles virus, mumps virus, rabies virus, and Ebola virus (Fig. 2.5 ).
What is virus symmetry?
Symmetry refers to the way in which capsomere units are arranged in viral capsid. Two kinds of symmetry are recognized in the viruses which corresponds to two primary shape ie. Rod and spherical shape of virus. Rod shaped virus have helical symmetry and spherical shaped virus have icosahedral symmetry.
What are the two main structures of a virus?
The simplest virions consist of two basic components: nucleic acid (single- or double-stranded RNA or DNA) and a protein coat, the capsid, which functions as a shell to protect the viral genome from nucleases and which during infection attaches the virion to specific receptors exposed on the prospective host cell.
What is the difference between helical and icosahedral viruses?
Lesson Summary A helical virus is a virus that has a capsid shaped in a filamentous or rod-shaped structure that has a central cavity that encloses its nucleic acid. An icosahedral virus is a virus consisting of identical subunits that make up equilateral triangles that are in turn arranged in a symmetrical fashion.
What is the size range of virions?
Virion properties Typically, virions are 19×50 nm, but range between 18 and 20 nm in width and 48 and 53 nm in length (Figure 1). Optical diffraction patterns of the virions resemble those of virions of Alfalfa mosaic virus, suggesting a morphological subunit diameter of about 10 nm and a T=1 icosahedral symmetry.
What is capsid function?
A primary function of the capsid is to protect the viral genome from environmental conditions and ultimately to deliver the genome to the interior of a homologous host cell.
What are the 2 major viral capsid types?
There are two major types of capsids. The first type is helical which can be described as spiral shaped. The second type is icosahedral shape which is a polygonal (20-sided) shaped capsid.
Is rabies a helical virus?
The rabies genome encodes five proteins: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and polymerase (L). All rhabdoviruses have two major structural components: a helical ribonucleoprotein core (RNP) and a surrounding envelope.
Which is largest virus?
Mimivirus is the largest and most complex virus known.