virology lecture 2 (viral structure)
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TRANSCRIPT
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Marilen M. Parungao-Balolong
Reference: Chapter 3 Carter And Saunders, 2007)
VIRAL STRUCTURE & CLASSIFICATIONS144 Lecture 2 (Virology)
http://www.virology.ws
Thursday, June 30, 2011
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winfoin.com
SKILLS, VALUES, OUTPUTS
✤ Listening, Writing and Oral Communication Skills
✤ Critical Analysis and Organization of Ideas
✤ Appreciate Importance of Viral Structure
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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LECTURE OUTLINE
✤ Recall: Viruses Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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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
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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
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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)
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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
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
bio3400.nicerweb.net
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VIRUS: INTRODUCTION
✤ Propagation depend on specialized host cells supplying the complex metabolic and biosynthetic machinery of eukaryotic or prokaryotic cells
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
ncbi.nlm.nih.gov
Thursday, June 30, 2011
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LECTURE OUTLINE
✤ Recall: Viruses Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
virology.ws
medical-dictionary.thefreedictionary.com
Thursday, June 30, 2011
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dvm5.blogspot.com
Reference: Chapter 3 Carter And Saunders, 2007)
Marilen M. Parungao-Balolong 2011
Thursday, June 30, 2011
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CORONAVIRUS STRUCTURE: SARS
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
http://learn.genetics.utah.edu/archive/sars/index.html
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THE CORE: GENOME
✤ 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)
Copyright © 1996, The University of Texas Medical Branch at Galveston.
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THE CORE: GENOME
✤ 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)
Copyright © 1996, The University of Texas Medical Branch at Galveston.
Thursday, June 30, 2011
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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)
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INTRODUCTION TO VIRUS STRUCTURE
✤ TYPES OF VIRION STRUCTURE
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
TYPES GENOMESGENOMESGENOMESGENOMES
dsDNA ssDNA dsRNA ssRNA
Icosahedral (naked)
Icosahedral (Enveloped)
Helical (naked)
Helical (Enveloped)
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Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
http://www.mansfield.ohio-state.edu/~sabedon/017vrgnm.gif
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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)
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ARRANGEMENT OF GENOME
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
GENOME EXAMPLEssDNA, linear ParvovirusdsDNA, linear Poxvirus
ssDNA, circular Phage X174dsDNA, circular Baculoviruses
ssRNA, linear Tobacco Mosaic VirusdsRNA, linear Reovirus
ssRNA, circular Hepatitis D virus
Note: there are no viruses known with circular dsRNA genomes
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USUALLY....
✤ FUNGI VIRUSES
✤ dsRNA
✤ PLANT VIRUSES
✤ ssRNA
✤ PROKARYOTIC VIRUSES
✤ dsDNAMarilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
sdnhm.org
http://www.whmsoft.net
topnews.in
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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)
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virology.ws
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
medical-dictionary.thefreedictionary.com
Take note of the nucleocapsid and envelope
THE CAPSID: PROTEIN CORE
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Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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.
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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
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
The helical structure of the rigid tobacco mosaic virus rod
Copyright © 1996, The University of Texas Medical Branch at Galveston.
Thursday, June 30, 2011
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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)
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MORPHOLOGY : Helical
✤ Details of the capsid structure are often discernible by electron microscopy
✤ NOTE: Helical nucleocapsids are characterized by length, width, pitch of the helix, and number of protomers per helical turn
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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
Copyright © 1996, The University of Texas Medical Branch at Galveston.
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MORPHOLOGY
✤ Icosahedral morphology is characteristic of the nucleocapsids of many “spherical” viruses
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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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 opposite edges.
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Icosahedral models seen, left to right, on fivefold, threefold, and twofold axes of rotational symmetry
Copyright © 1996, The University of Texas Medical Branch at Galveston.
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MORPHOLOGY
✤ Viruses were first found to have 532 symmetry by x-ray diffraction studies
✤ Electron microscopy with negative-staining techniques
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Adenovirus after negative stain electron microscopy
Copyright © 1996, The University of Texas Medical Branch at Galveston.
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MORPHOLOGY
✤ PROTOMERS:
✤ structural polypeptide chains
✤ arranged in oligomeric clusters (capsomeres)
✤ readily delineated by negative staining electron microscopy
✤ form the closed capsid shell
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Adenovirus after negative stain electron microscopy
Copyright © 1996, The University of Texas Medical Branch at Galveston.
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THE CAPSOMERES
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
pc.maricopa.edu
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CAPSOMERES & ENVELOPE
✤ The number and arrangement of the capsomeres are useful in identification and classification
✤ Many viruses also have an outer envelope
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
Envelope of Herpesvirus
biologie.uni-hamburg.de
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CAPSID & ENVELOPE
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
pc.maricopa.edu
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Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
THE ENVELOPE
✤ Envelope consists of a lipid bilayer with proteins (usually glycoproteins) imbedded in it
✤ 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
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Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
ENVELOPED VIRUSES
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Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
COMPLEX VIRUSES
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LECTURE OUTLINE
✤ Recall: Viruses Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
bbc.co.uk
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STRUCTURE IN RELATION TO FUNCTION
✤ Core
! ! ! a.! DNA or RNA
! ! ! b.! Contains genetic
information
! !
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
ncbi.nlm.nih.gov
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STRUCTURE IN RELATION TO FUNCTION
✤ 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)Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
sparknotes.com
library.thinkquest.org
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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
✤ Derived from host bell membrane during viral multiplicationMarilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
microscopicblog.blogspot.com
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STRUCTURE IN RELATION TO FUNCTION
✤ 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)
wpro.who.int
me-you-and-virus.blogspot.com
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LECTURE OUTLINE
✤ Recall: Viruses Introduction
✤ Structure of Viruses
✤ Functional Anatomy
✤ Classification
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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✤ 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)
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PLANT VIRUSES
Marilen M. Parungao-Balolong 2011 Reference: Chapter 13 TortoraMicrobiology
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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)
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CLASSIFYING VIRUS BASED ON GENOME...
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
antiviralintelistrat.com
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Date
END OF LECTURE 2
Marilen M. Parungao-Balolong 2011 Reference: Chapter 3 Carter And Saunders, 2007)
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