The document summarizes a lecture on viral structure and classification. It outlines the structure of viruses including the core, which contains the viral DNA or RNA genome, capsids made of protein subunits, and some viruses also have an outer envelope. It also discusses different viral morphologies like helical and icosahedral shapes. The lecture covers the relationship between viral structure and function.

1. http://www.virology.ws
VIRAL STRUCTURE & CLASSIFICATION
S144 Lecture 2 (Virology)
Marilen M. Parungao-Balolong
Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

2. SKILLS, VALUES, OUTPUTS
✤ Listening, Writing and
Oral Communication winfoin.com
Skills
✤ Critical Analysis and
Organization of Ideas
✤ Appreciate Importance
of Viral Structure
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

3. LECTURE OUTLINE
✤ Recall: Viruses
Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

4. REFERENCES
✤ Carter and Saunders, 2007 (Chapter 3)
✤ Gelderblom, 2010 (Chapter 41)
✤ (Bookshelf ID: NBK8174 PMID: 21413309)
✤ http://www.ncbi.nlm.nih.gov/books/NBK8174/
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

5. LECTURE OUTLINE
✤ Recall: Viruses
Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

6. VIRUSES: INTRODUCTION
✤ Viruses are small
obligate intracellular
parasites
✤ Contain either a
RNA or DNA
genome surrounded
by a protective,
virus-coded protein
coat
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

7. VIRUSES: INTRODUCTION
✤ Viruses may be viewed as mobile genetic elements, most probably of
cellular origin and characterized by a long co-evolution of virus and
host
bio3400.nicerweb.net
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

8. VIRUS: INTRODUCTION
✤ Propagation
depend on
specialized host
cells supplying
the complex
metabolic and
biosynthetic
machinery of
eukaryotic or ncbi.nlm.nih.gov
prokaryotic cells
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

9. LECTURE OUTLINE
✤ Recall: Viruses
Introduction
✤ Structure of Viruses virology.ws
✤ Functional Anatomy
✤ Classification
medical-dictionary.thefreedictionary.com
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

10. Reference: Chapter 3 Carter And Saunders, 2007)
Marilen M. Parungao-Balolong 2011 dvm5.blogspot.com
Thursday, June 30, 2011

11. CORONAVIRUS STRUCTURE:
SARS
http://learn.genetics.utah.edu/archive/sars/index.html
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

12. THE CORE:
GENOME
Copyright © 1996, The University of Texas Medical Branch at Galveston.
✤ Except in helical
nucleocapsids, little is
known about the
packaging or
organization of the viral
genome within the core
✤ SMALL VIRIONS:
✤ simple nucleocapsids
✤ containing 1 to 2
protein species
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

13. THE CORE:
GENOME
Copyright © 1996, The University of Texas Medical Branch at Galveston.
✤ LARGE VIRIONS:
✤ nucleic acid
genome
complexed with
basic protein(s)
✤ protected by a
single- or double
layered capsid or
by an envelope
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

14. CHEMICAL COMPOSITION OF
GENOME
✤ The genome of a virus may consist of DNA or RNA,
which may be single stranded (ss) or double stranded
(ds), linear or circular
✤ The entire genome may occupy either one nucleic acid
molecule (monopartite genome) or several nucleic acid
segments (multipartite genome)
✤ The different types of genome necessitate different
replication strategies
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

15. INTRODUCTION TO VIRUS
STRUCTURE
✤ TYPES OF VIRION STRUCTURE
TYPES GENOMES
dsDNA ssDNA dsRNA ssRNA
Icosahedral
(naked)
Icosahedral
(Enveloped)
Helical (naked)
Helical
(Enveloped)
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

16. http://www.mansfield.ohio-state.edu/~sabedon/017vrgnm.gif
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

17. VIRUS GENOMES
✤ dsDNA
✤ encode their genes in the same kind of
molecule as animals, plants, bacteria and
other cellular organisms
✤ ssDNA, dsRNA, ssRNA
✤ unique to viruses
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

18. ARRANGEMENT OF GENOME
GENOME EXAMPLE
ssDNA, linear Parvovirus
dsDNA, linear Poxvirus
ssDNA, circular Phage X174
dsDNA, circular Baculoviruses
ssRNA, linear Tobacco Mosaic Virus
dsRNA, linear Reovirus
ssRNA, circular Hepatitis D virus
Note: there are no viruses known with circular dsRNA genomes
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

19. USUALLY....
✤ FUNGI VIRUSES
✤ dsRNA sdnhm.org
topnews.in
✤ PLANT VIRUSES http://
www.whmsoft.net
✤ ssRNA
✤ PROKARYOTIC VIRUSES
✤ dsDNA
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

20. POINTS TO REMEMBER...
✤ Some linear molecules may be in a
circular conformation as a result of base
pairing between complimentary
sequences at their ends
✤ Example:
✤ DNA in Hepadnavirus
✤ RNA in Influenza virions
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

21. THE CAPSID: PROTEIN CORE
virology.ws medical-dictionary.thefreedictionary.com
Take note of the nucleocapsid and envelope
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

22. THE CAPSID: PROTEIN CORE
Structure of adenovirus. The icosahedral capsid structure of
adenovirus is made up of three proteins, hexon, penton
base, and fiber. A cross-sectional view of the viral capsid.
Some proteins are associated with viral DNA, whereas
others are associated with hexon and are involved in the
formation of the capsid.
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

23. MORPHOLOGY : Helical
✤ Helical morphology is seen in
nucleocapsids of many
filamentous and pleomorphic
viruses
✤ Helical nucleocapsids consist
of a helical array of capsid
proteins (protomers) wrapped
around a helical filament of
nucleic acid The helical structure of the rigid tobacco mosaic virus rod
Copyright © 1996, The University of Texas Medical Branch at Galveston.
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

24. MORPHOLOGY : Helical
✤ In the replication of viruses
with helical symmetry,
identical protein subunits
(protomers) self-assemble
into a helical array
surrounding the nucleic
acid, which follows a
similar spiral path
✤ Nucleocapsids form rigid,
highly elongated rods or
flexible filaments
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

25. MORPHOLOGY : Helical
✤ Details of the capsid
structure are often
discernible by electron
microscopy
✤ NOTE: Helical
nucleocapsids are
characterized by length, Fragments of flexible helical nucleocapsids (NC) of Sendai
virus, a paramyxovirus, are seen either within the protective
envelope (E) or free, after rupture of the envelope
width, pitch of the helix, and
Copyright © 1996, The University of Texas Medical Branch at Galveston.
number of protomers per
helical turn
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

26. MORPHOLOGY
✤ Icosahedral
morphology is
characteristic of
the
nucleocapsids of
many
“spherical”
viruses
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

27. MORPHOLOGY
✤
Lines through opposite
vertices define axes of fivefold
rotational symmetry: all
structural features of the
polyhedron repeat five times
within each 360° of rotation
about any of the fivefold axes
✤
Lines through the centers of
opposite triangular faces form
axes of threefold rotational
symmetry; twofold rotational
symmetry axes are formed by
lines through midpoints of Icosahedral models seen, left to right, on fivefold,
opposite edges. threefold, and twofold axes of rotational symmetry
Copyright © 1996, The University of Texas Medical Branch at Galveston.
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

28. MORPHOLOGY
✤ Viruses were first
found to have 532
symmetry by x-ray
diffraction studies
✤ Electron
microscopy with Adenovirus after negative stain electron microscopy
negative-staining Copyright © 1996, The University of Texas Medical Branch at Galveston.
techniques
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

29. MORPHOLOGY
✤ PROTOMERS:
✤ structural polypeptide
chains
✤ arranged in oligomeric
clusters (capsomeres)
✤ readily delineated by
negative staining Adenovirus after negative stain electron microscopy
electron microscopy Copyright © 1996, The University of Texas Medical Branch at Galveston.
✤ form the closed capsid
shell
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

30. pc.maricopa.edu
THE CAPSOMERES
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

31. CAPSOMERES & ENVELOPE
✤ The number and
arrangement of the
capsomeres are useful
in identification and
classification
✤ Many viruses also
have an outer Envelope of
envelope Herpesvirus
biologie.uni-hamburg.de
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

32. CAPSID & ENVELOPE
pc.maricopa.edu
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

33. ✤ Envelope consists of a
lipid bilayer with proteins
(usually glycoproteins)
imbedded in it THE ENVELOPE
✤ Lipids derived from
host cell
✤ Proteins encoded by the
virus
✤ Envelope is important in
determining host cell
specificity & some aspects
of cell penetration are
affected by it
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

34. ENVELOPED VIRUSES
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

35. COMPLEX VIRUSES
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

36. LECTURE OUTLINE
✤ Recall: Viruses
Introduction
✤ Structure of Viruses
✤ Functional Anatomy
bbc.co.uk
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

37. STRUCTURE IN RELATION TO
FUNCTION
✤ Core
! ! ! a.! DNA or RNA
! ! ! b.! Contains genetic
information
ncbi.nlm.nih.gov
!!
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

38. STRUCTURE IN RELATION TO
FUNCTION sparknotes.com
✤ Capsid
! ! ! a.! Outer protein coat
! ! ! b.! Functions
! ! ! ! 1).!Protects core
! ! ! ! 2).!Shape of the virus
! ! ! ! 3).!Attachment to host
cell membrane (by means of
spikes) library.thinkquest.org
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

39. STRUCTURE IN RELATION TO
FUNCTION
✤ Envelope
✤ Membrane around capsid - enveloped virus
✤ Not all viruses have envelope
✤ If lack envelope - naked virus!
✤ Composed of:
✤ Bilayer of phospholipids and proteins microscopicblog.blogspot.com
✤ Derived from host bell membrane during viral multiplication
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

40. STRUCTURE IN RELATION TO
FUNCTION me-you-and-virus.blogspot.com
wpro.who.int
✤ Functions :
✤ Protection from drying (enhances
transmission)
✤ Makes virus more susceptible to
chemical agents that dissolve lipids
✤ Attachment to host cell membrane
(by means of spikes)
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

41. LECTURE OUTLINE
✤ Recall: Viruses
Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

42. ✤ Viruses are grouped on the basis of size and shape, chemical
composition and structure of the genome, and mode of replication
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

43. PLANT VIRUSES
Marilen M. Parungao-Balolong 2011 Reference: Chapter 13 TortoraMicrobiology
Thursday, June 30, 2011

44. CLASSIFYING ENVELOPED
VIRUS BASED ON SHAPE...
✤ Sphere (eg. Influenza
virus)
✤ Bullet (e.g. Rabies
virus)
✤ Rod (e.g. Baculovirus)
✤ Thread (e.g Ebola
virus)
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

45. CLASSIFYING VIRUS BASED
ON GENOME...
antiviralintelistrat.com
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011

46. END OF LECTURE 2
Date
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Thursday, June 30, 2011