Biology 421/521: Virology : Lecture 6, 11 October 2002

Last Updated: 10/11/02 at 1:13 PM

Outline

• Virus Structure
  • Envelope Proteins
  • Enzymes
  • Other (Viral and Cellular) Proteins
  • Review
• RNA Virus replication
  • RNA dependent RNA polymerases
  • Structures

Viral Envelopes

• All contain lipids from host
  • Phosphodiesters
  • From different intracellular compartments
• All contain viral glycoproteins

Viral Membrane Proteins

• Integral Membrane Proteins
• Many have attached oligosaccharides
• Often Oligomeric
• Extracellular domains
  • Receptors
  • Antigenic determinants
  • Fusion domains
• Intracellular
  • Virus assembly
• Figure 3.19

Influenza Hemagglutinin

• Coiled coil trimer
• Projects 13.5 nm from envelope
• Receptor binding
• Entry of virus particle
• Huge conformational change (like the E-protein)
• Figure 3.20

Other envelope proteins

• Retroviruses
  • Env proteins
• Herpesvirus
  • At least 10

Togaviruses

• Probably simplist enveloped virus
• T =4 (C-protein of nucleocapsid)
  • Does not have beta-barrel structure but is a protease
• Glycoprotein contacts C directly
• Figure 3.21

What happens between envelope and core?

• Ocassionally matrix protein
  • (-) ss RNA viruses
  • Appendix Figs 5, 7, 9
• Herpesvirus Teguement
  • > 8 proteins
• Few structures!
  • Mutational analysis
  • in vitro assays
  • 3D structures of fragments
  • Figure 3.22

Other virus components

• Enzymes
  • RNA polymerases
    • RNA-dependent
      • All (-) strand RNA viruses
    • Reverse Transcriptase
    • DNA dependent
      • Vaccinia
  • Proteases
  • Cap-Endonuclease (Influenza)
• Transcription Factors

Cellular proteins

• Histones (SV40)
• Cyclophilin (HIV-1)
  • peptidyl-prolyl cis-trans isomerase
  • Helps fold proteins
  • Present with Gag protein
  • Seems to be important

Review

• Virions want to be as small as possible
• The coat must protect and deliver
• Primary/Secondary/Tertiary/Quaternary protein structures
• Structure determination
  • Cryo-Electron Microscopy
  • Nuclear Magnetic Resonance
  • X-ray crystallography
  • Difference Imaging
• Helical vrs icosahedral symmetry
• Icosahedral Symmetry
  • Quasi-equivalence, Triangulation number
  • Polio virus - Picornavirus
  • SV-40 - Papovavirus
  • Herpesvirus - Tegument
  • Adenovirus - Many protein
  • Reoviridae - 2 shells
• Genome packaging
• Envelopes and their proteins
• Other components