Basics of TMV and HIV

1. Shri Shivaji Education Society, Amravati’s
SHRI SHIVAJI COLLEGE OF ARTS, COMMERCE AND SCIENCE, AKOLA
NAAC Reaccredited with A grade ( CGPA 3.24), College With Potential For Excellence and Lead College ( Status by
SGBAU, Amravati) DIST FIST Support
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©Anand Oke

2. Department of Botany
SHRI SHIVAJICOLLEGEOFARTS, COMMERCE AND SCIENCE,
AKOLA
©Anand Oke
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3. Dr. Anand V. Oke
Assistant Professor,
Department of Botany,
Shri Shivaji College of Art’s, Commerce and Science, Akola.

4. tmV & HIV
Dr. Anand V. Oke
Assistant Professor,
Department of Botany,
Shri Shivaji College of Art’s, Commerce and Science, Akola 4

5. Tobacco Mosaic Virus
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6. Structure
• Virus particles/virions are strait, rigid and cylendrical rods
• Helical and remarkably uniform architecture
• 18 nm diameter and 300 length
• Rods hollow
• Cavity 4 nm wide and throughout
• 14 nm thick capsid wall
• Outer protective coat called Capsid
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7. • Inner infectious agent genetic material/ nucleic acid present throughout
the virion
• Capsid made up of about 2200 similar protein subunits called Capsomere
• Capsomere packed regularly in left handed helix
• Virus- 95 % protein and 5 % RNA
• Proteins and RNA are coaxially interwined to form rod shaped virion
• Capsomeres are made up of proteins similar to other plant proteins
• Molecular weight is about 40 million
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8. • RNA 2 million mol. weight and provides code for amino acid sequence of
capsids
• Capsomere 17400 mw. and made up of condensation of 158 aa residues
• Virus remains particle active for 50 years in dried tobacco leaves
• Witstand boiling for 10 min
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9. HIV
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10. • The HIV is the cause of one of the most destructive human pandemics in
recorded history.
• Since it was first recognised in 1981 it has killed more than 25 million
people.
• Conservative estimates suggest that 33 million people are currently infected
and 60% of them live in sub-Saharan Africa.
• UK (2007)- 77,400 HIV positive people
• There is often confusion between the terms AIDS and HIV.
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11. • AIDS- set of symptoms that occured in the final stage of HIV infection
• AIDS occurs when the virus has destroyed the immune system,
• leave the patient highly susceptible to other life threatening infections.
• People infected with HIV are referred ‘HIV positive’, they do not
necessarily have any symptoms of disease.
• With the advent of new drug regimes, it is now hoped that many HIV
positive people may never reach the AIDS stage.
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12. • HIV is an RNA virus known as a retrovirus.
• Central core containing two identical RNA genomes
• Enzymes like reverse transcriptase, protease and integrase are present
• Capsid covered by a lipid bilayer with glycoprotein spikes.
• Two major strains of HIV.
• HIV-1- cause majority of the infections and easily transmitted than HIV-2
• HIV-2 is restricted to West Africa, although there are imported cases in the
UK.
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13. Retrovirus
• Retroviruses are capable of carrying out transcription in reverse direction
• It contain an enzyme called reverse-transcriptase
• It ranscribes the viral RNA into DNA.
• DNA is then be inserted into the genome of the host cell, where it stays for
the lifetime of the cell.
• The cell synthesises viral RNA and proteins, allowing the virus to multiply
inside the host cell.
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14. Resistance
• Some people are naturally resistant to HIV infection due to a mutation in
the gene coding for a protein called CCR5.
• This is found on the cell surface of some white blood cells and is a receptor
for chemicals called cytokines that help regulate the immune system.
• Homozygous individuals do not express the receptor on their cells and are
completely resistant to HIV infection.
• Heterozygous individuals show partial resistance and if they do become
infected the disease progresses more slowly.
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15. • The mutation is thought to exist in 10% of people of European origin, but is
not found in people with African, Asian, Middle Eastern or Native
American roots, but its(mutation) absence in other populations suggests
that it occurred relatively recently (within the past 2000 years).
•
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16. Structure
• HIV consists of a cylindrical centre surrounded by a sphere-shaped lipid
bilayer envelope.
• There are two major viral glycoproteins in this lipid bilayer, gp120 and
gp41.
• The major function of these proteins is to mediate recognition of CD4+
cells and chemokine receptors, thereby enabling the virus to attach to and
invade CD4+ cells.
• The inner sphere contains two single-stranded copies of the genomic RNA,
multiple proteins and
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17. • Enzymes necessary for HIV replication and maturation like p24, p17,
reverse transcriptase, integrase, and protease.
• HIV uses 9 genes to code for the necessary proteins and enzymes.
• Three principal genes are gag, pol, and env.
• The gag gene encodes core proteins.
• The pol gene encodes the enzymes reverse transcriptase, protease, and
integrase.
• The env gene encodes the HIV structural components known as
glycoproteins.
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18. • The rest of the genes like rev, nef, vif, vpu, vpr, and tat are important for
viral replication and enhancing HIV’s infectivity rate.
• HIV (human immunodeficiency virus) is composed of two strands of RNA,
15 types of viral proteins, and a few proteins from the last host cell it
infected, all surrounded by a lipid bilayer membrane.
• These molecules allow the virus to infect cells of the immune system and
force them to build new copies of the virus.
• Each molecule in the virus plays a role from the first steps of viral
attachment to the final process of budding.
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19. Viral enzymes
• RT: Reverse transcriptase builds a DNA copy of the viral RNA genome,
which is then used to build new viruses. This structure captures the enzyme
as it is building a DNA strand (red) from the viral RNA (yellow). It will
then destroy the RNA and build a second DNA strand.
• IN: Integrase takes the DNA copy of the viral genome and inserts it into
the infected cellular genome. In this way, HIV can lie dormant in cells for
decades, making it incredibly difficult to fight
• PR: HIV protease is essential for the maturation of HIV particles. The
proteins in HIV are built as long polyproteins, which then must be cleaved
into the proper functional pieces by HIV protease
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20. Structural proteins
• MA: Matrix protein forms a coat on the inner surface of the viral
membrane.
• It plays a central role when new viruses bud from the surface of infected
cells
• CA: Capsid protein forms a cone-shaped coat around the viral RNA,
delivering it into the cell during infection.
• It forms stable hexamers, which then assemble like tiles to form geodesic
capsids.
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21. • SU and TM: Envelope proteins gp120 and gp41 bind to receptors on the
surface of cells that HIV infects, and then penetrate the surface to infect it
with the viral RNA.
• The spikes formed by these proteins are highly decorated with
carbohydrates, making them difficult to recognize by antibodies
Accessory proteins
• Vpu - (viral protein u) helps the virus escape the cell during budding by
weakening the interaction of the new envelope proteins with cell receptors
• P6- is involved in the incorporation of Vpr into new viruses
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22. • Vif- (viral infectivity factor) attacks one of the cell's defense proteins,
which forces the cell to destroy it.
• Vpr- (viral protein r) guides the viral genome into the nucleus following
infection
• Nef- (negative regulatory factor) forces the infected cell to stop making
several proteins that are important in cell defense
• Rev- (regulator of virion) protein binds to a hairpin in the viral RNA and
regulates the splicing and transport of viral RNA.
• Tat- (trans-activator of transcription) protein binds to a hairpin in the viral
RNA and greatly enhances the amount of protein that is made
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23. References
• G.R. Carter, D. J. Wise and E. Furtado Flores;General Characteristics, Structure and
Taxonomy of Viruses;A Concise Review of Veterinary Virology,Publisher: International
Veterinary Information Service (www.ivis.org), Ithaca, New York, USA.
• Vashishtha B.R; Sinha A.K.(2014)Botany for degree students, Fungi,; S. Chand
publications;623-24
• Nancy R. Calles, Desiree Evans, De Louis Terlonge; Pathophysiology of the human
immunodeficiency virus; HIV Curriculum for the Health Professional
• Gemma Sims (2009) HIV and AIDS- A resource for secondary schools, The Society of
general microbiology
• Annonemou (2011). The Structural Biology of HIV, RCSB Protein Data Bank
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