Virus - Basics & News Taxonomy & Families

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Presentation transcript:

Virus - Basics & News Taxonomy & Families What is a virus ? Structure Genome Replication

A virus is a virus (lat: poison) Replication: a replicating biochemical complex without its own metabolism requires metabolism of living host cell for replication Structure: Submicroscopic Size, 30 - 150 nm (exception:orthopox) Genome: contains genetic information, DNA or RNA

Virus - sizes

Comparison of Size: Virus/Bakterium

An infectious virus particle ‘Virion‘ The genome (DNA or RNA) is always packed in a protein structure the ‘Capsid‘ The combine Capsid/Genomestructure: ‘Nukleocapsid‘ The capsid structure can be spherical (Icosaeder) or helical structure (Tubulus) Some viruses have additional structures: a lipid envelope engulfing the capsid

non enveloped Virus: contains only nucleic acid and protein Tobacco mosaic virus: helical capsid Adenovirus: icosahedral capsid

‘enveloped viruses‘ Herpes Simplex Virus Paramyxovirus For enveloped viruses, the lipid envelope is always essential for infectivity. The envelops can be easily destoyed by ether & detergents

Spherical capsids have an icosahedral structure An Icosahedron has 20 triangular surfaces and three axes of symmetry Picornavirus: 5-fold axes of smmetry animated X-Ray structure

Icosahedral capsids are built from capsomers: Icosahedral capsids are built from capsomers: identical units of the same proteins X-Ray structure capsid of picornaviridae

The capsid surface of non enveloped viruse must carry structures for binding to cellular receptors These both (non related) viruses bind to CAR but the binding structures look very different ‘Canyons‘ for binding to CAR (many enterovirus types) Fiber (‘Spikes‘) for binding to CAR (many adenovirus types)

Comparison: replication of virus vs. bacterium obligat intrazellulär NIE auf Nährmedien, Agars usw. lebende Zellen erforderlich: Versuchstier Brutei Zellkultur Eklipse bzw. Latenzperiode, Adsorption, Penetration, Uncoating Proteinsynthese & Genomreplikation Assembly & Virusfreisetzung

Classical Concept of ICTV taxonomy system: family/genus/species family names: ...-idae relevant for virus family: genome type (DNA, RNA; ds-, ss-, ) capsid structure (helical, icosahedral) enveloped/non enveloped

RNA viruses RNA-Virus

DNA viruses DNA-Virus

Baltimore System way of mRNA production (->Proteinsynthesis) DNA Virus RNA Virus

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