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Structural Virology
Lecture 2
Pavel Plevka
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Infectious virus particle “virion”
Carrier of genetic information from cell to cell:
- "extracellular organelle”
- packages viral genome
- escapes from infected cell
- survives transfer from cell to cell
- attaches, penetrates, initiates
replication in new host cell
Helical Icosahedral
Complex
Irregular
Virus structures
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Pitch
Pitch is the distance along the helix axis
for one complete helix turn
Twist is the rotation between
neighboring nucleotides
Twist
Helical symmetry
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T = h2 + hk + k2
Quasi equivalence
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Quasi equivalence
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Quasi-equivalence
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Equivalence
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Equivalence
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Quasi equivalence
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Quasi equivalence
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Quasi equivalence
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Quasi equivalence
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Quasi equivalence
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Quasi equivalence
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beta-strand beta-strand
Primary
structure
Secondary
structure
Tertiary
structure
Quaternary
structure
Levels of description of protein structures
Motif
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Levels of description of RNA structures
Picornavirus virion
Plevka et al. Science 2012.
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Molecular components of virions
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DNA genomes of viruses
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RNA genomes of viruses
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Pandoravirus 1.1-2.5MB
TNSV 1239B (RNA)
Coronaviruses 33kB (RNA)
Hepatitis B virus 3.2kB
Phage lambda 48kB
Mimivirus 1.2MB
Sizes of virus genomes
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Genomes of cellular organisms (kB)
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Secondary structures in ssRNA genomes
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Internal Ribosome Entry Site in poliovirus
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Modifications of genome ends
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More end modifications (ssRNA)
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dsRNA genome modifications
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(Macro)-molecules non-covalently
associated with virus genomes
Zinc finger motif Histone core
Poly amine - putrescine
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Terminal repeats in virus genomes
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Adenovirus virion Phage T7
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• describe the components of virions
• illustrate the variety of virus genomes
• outline the functions of virus structural
proteins
• define the terms ‘helical symmetry’ and
‘icosahedral symmetry’
• describe the virions of a selection of naked
and enveloped viruses
Learning outcomes
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Why / when / for what are
structures important?
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Virus transmission
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Insects
Mites
Nematodes
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Baculovirus transmission
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Non-vector transmission of vertebrate viruses
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Virus infection X cell cycle
Retroviruses
Polyomaviruses, papillomaviruses
Restriction endonucleases
RNAi response, CRISPR / Cas, antibodies, NK cells
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• describe the modes of transmission of plant
viruses and animal viruses
• evaluate the roles of vectors in virus
transmission
• discuss the immune mechanisms encountered
by an animal virus when it enters the body of
a new host
Learning outcomes
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Attachment and entry of viruses into cells
1. Attachment
2. Entry
3. Transcription
4. Translation
5. Genome replication
6. Assembly
7. Exit
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Virus receptors
Echovirus 7 in
complex with DAF
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Attachment and entry of a naked virion
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Attachment and entry of an enveloped virion
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Virus membrane fusion
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Virus membrane fusion
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Intracellular transport of viruses
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Intracellular transport of viruses
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Phage MS2 infection
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Phage phi812 genome injection
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• outline a generalized scheme of virus
replication involving seven steps
• describe how animal viruses attach to and
enter their host cells
• differentiate between the entry mechanisms
of naked and enveloped animal viruses
• describe the roles of cell components in the
delivery of viral genomes to the nucleus
• outline the infection mechanisms of phages
Learning outcomes