Transcript Tobacco Mosaic Virus (TMV)

Tobacco Mosaic Virus (TMV)
Presentation by Tristan Vranizan
History
• TMV: the first virus to be discovered
• Late 19th Century: Researchers found out that a
tiny infectious agent was the cause of a disease
that was killing tobacco plants.
• Wendell Stanley coaxed the virus to form crystals
and found out that it was mainly composed of
proteins.
• RNA (Ribonucleic acid) was also discovered in
the virus
Wendell Stanley >>
Won Nobel prize for his study.
Description of Molecule
• TMV has one strand of RNA, shown
in red.
• RNA is wrapped with stacks of
protein, shown in blue.
• Protein Coat: 2,130 copies of a small
protein stack on top of each other,
spiraling downward.
• RNA strand is encoded in four
proteins, transporting the RNA from
cell to cell and allowing the virus to
spread.
Infection
• TMV is so stable it can survive in cigars for years made
from infected tobacco leaves.
• The coat of proteins, around the RNA strand, protect it
from any enzymes trying to kill it.
• But, in order for TMV to spread it has to release it’s coat of
proteins for the RNA to enter a cell
• The proteins, situated outside the cell, repel against each
other. This allows the cell to release RNA back into the
coat of proteins to spread again.
Healthy tobacco leaf >
< TMV infected leaf
Assembly
• Mixing RNA with capsid proteins creates a
functional virus.
• Two steps create this process
• Step 1: Proteins form into a two-layer disk, RNA
then fills the hole at the center causing the proteins
to form into a ring, eventually covering the RNA.
• Step 2: RNA is ensured to being packaged into
viruses with its’ need for an initiation sequence.
Structure
• 17 subunits surround the RNA in red.
• RNA is located in the grooves of the
protein, wedged between them.
• 3 nucleotides bind each protein subunit.
Structure (continued)
• The bright red dots are the acidic amino
acids.
• They help to break up the virus inside
infected cells.
Other plants with TMV
Picture References
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http://erec.ifas.ufl.edu/tomato-scouting-guide/images/diseases/tobacco-mosaic135.JPG
http://erec.ifas.ufl.edu/tomato-scouting-guide/diseases/tobacco-mosaic-virus.shtml
http://matyasciprian.hu/kepek/paprika_betegsegek/paprika_tmv_3.JPG