MICRO CH6

MICRO CH6 - Chapter 6- Virus Structure and Function General...

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Chapter 6- Virus Structure and Function General Properties of Viruses (virions) Obligate intracellular parasite made of nucleic acid surrounded by a protein coat. Only replicate inside host No nucleus, organelles, cytoplasm Viral genomes contain information for taking over host cell information for making viral proteins Capsid, genome replication proteins Virus Structure—Capsids Capsid- protein coat surrounding nucleic acid Capsid proteins are arranged to give virion symmetry Icosahedral capsids Roughly spherical 20 equilateral triangles or faces polio, herpes Filamentous capsids ( M13, Ebola) Long tube of protein, with genome inside Tube made up of 100’s of identical protein subunits Tube length reflects size of viral genome Complex capsids Mixture of icosahedral & filamentous shapes Many bacteriophage (Viruses that infect bacteria) Asymmetrical (irregular) shapes Tend to be larger viruses Poxviruses
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Cow pox TEM of bacteriophage T4. Capsid has been disrupted by Virus Structure—Envelopes Envelope- lipid bilayer around capsid of some viruses Allows fusion to host cell membrane Only occurs if host cell not covered by cell wall Bacteriophages are NON-enveloped Envelope lipids come from host Not encoded by viral genome Proteins embedded in envelope may be encoded by virus Coats viral capsid as virus leaves cell Human wart virus, TMV (filamentous) Cold virus, smallpox, rhabdovirus Virus Structure—Genome DNA or RNA Includes genes encoding viral proteins Capsid Envelope proteins if virus is enveloped Any polymerase not found in host cell (has to provide its own enzymes for polymerase for RNA) International Committee on Taxonomy of Viruses classification system based on: 1. Genome composition DNA or RNA Single or double stranded Linear or circular Whole (one piece) or segmented (different pieces, INFLUENZA) Classified by Baltimore method 2. Capsid symmetry
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helical or icosahedral 3. Envelope - Presence or absence of host derived envelope 4. Size of virus particles - Related viruses are similar in size 5. Host range - Related viruses infect same or related hosts Baltimore virus classification based on genome structure Group I - double stranded DNA (their DNA is just like their host) - herpesvirus group - cold sores, venereal disease, chicken pox (different viruses form
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This note was uploaded on 02/23/2012 for the course BIOL 2051 taught by Professor Brininstool during the Fall '07 term at LSU.

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MICRO CH6 - Chapter 6- Virus Structure and Function General...

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