Understanding Virus Structure

1.3 Virus Structure 1.3.1 Virus Particle Structure Viruses are veryvirus smallisinsmaller size. When compared to the wavelength of visible light, the size of the so the virus can only be seen clearly using anof electron microscope. Parvovirus is one of the smallest viruses with a diameter 18-22 nm. that Thiscauses virus attacks tobacco plants and causes tobaccolarvae necrosis disease. The virus denso nucleosis in Galleria mellonella has a size of 20 ± 1.5 nm and foot and mouth disease in livestock has a size of 22 nm. Apart from that, thereanimals is a virus that has the largest size, namely, entomopoxvirus which attacks and insects. Entomopoxvirus is a group of smallpox viruses that has a size of 400 x 250 nm. 1.3.2 Virus Genome (Virus Genome) The nucleic acid core (genome) of viruses contains genetic material, namely DNA or RNA. The type of viral genetic material is one of the most important factors ina site classifying viruses. Viruses with DNA genetic general materialpatterns utilize infected cells as for genome replication. There are several ofoccur gene expression and genome replication with similarities to the processes that in host cells. Viruses that material, use RNA asthisgenetic material have designed various ways to replicate this genetic is because cells do not have a complex system or wayof tospecific replicate RNA directly. Replication of viral RNA requires the expression enzymes which are only present in infected host cells. 1.3.3 Virus Capsid (Virus Capsid) Capsids have a are complex structure and are made of several identical protein subunits which often called capsomeres. The capsid functions as a protein framework in which the structurally unstable viral genome can be maintained and its stability in the environment. Theenergetically fusion of thestable capsidstructure. with theThis genome is astructure complex process which produces an stable can describe the dimensional shape of the virus. Based onregular the structural parameters ofandtheicosahedron. viral capsomere, the virusishas two types of shapes, namely helix Helix (Helical) a form ofnucleoprotein. combinationThe of capsid and nucleic acid incantheproduce form ofa rigid a helixor orflexible often shape, called combination of the two depending on thein nature Icosahedron (Icosahedral) isgenome. a capsomere the formof the of acapsid regularprotein dense itself. structure that encloses the viral The structure of ofthevirus capsid that Each surrounds the agenetic material of structural the virus makes each type unique. virus has unique shape and arrangement that dependsTheonshape the nature of thecapsid capsidis the protein and how the capsid protein interacts. of the viral basic criterion for classifying viruses. Apart from that, the viral capsid has several important roles, especially in the virus infection cycle. Following are some of the important roles of viral capsids: 1. The capsid protects the viral genome from all forms of exposure to the external environment 2.hostThecell. capsid facilitates with the host cell in termstissues of recognizing the Viruses exhibitinteraction their biological potential in specific of host cells 3.organisms. Capsids Sohelp movementcauses of viruses multicellular this the phenomenon systemicbetween infectioncells in hostin cells 4.In The capsid facilitates viral vector-mediated transmission with theoforganism. vectors, the capsid together with other proteins allows retention virions in the mouth of the vector, movement to other parts of the vector body, replication and sometimes the production of more virions.