lecture 4

Question 1

What is a capsomere made of?

Answer 1

promoters

Question 2

How is an enveloped virus structured?

Answer 2

matrix proteins attach the envelope to the nucleocapsid

Question 3

What is a tegument? Which virus has this?

Answer 3

Tegument is many different matrix proteins instead of just one. This can be found in herpes

Question 4

What is the function of the core in a virus?

Answer 4

carries genetic material and associated proteins that allow RNA/DNA to be replicated in the next cell, may have polymerase ((-)ssRNA)

Question 5

What is the function of the capsid in a virus?

Answer 5

protect nucleic acid from degradation
on a naked virus, the capsid has VAP

Question 6

What is function of the envelope in viruses?

Answer 6

contains viral attachment proteins
allows easy entry into cell via membrane fusion
helps mask virus from immune system

Question 7

What is the average size of a human, e.coli and virus genome

Answer 7

human: 10k-100k nb
e.coli: 500-1000 nb
virus:200-350 nb

Question 8

What three methods were used to determine virus structure?

Answer 8

electron microscopy, X-ray crystallography, cryo EM

Question 9

What is electron microscopy

Answer 9

stain virus and shoot with electrons, looking for negative staining

Question 10

what is X-ray crystallography?

Answer 10

identical repeating units with x-ray, leaves shadow, requires perfect imaging to which is hard

Question 11

what is cryoEM

Answer 11

freeze and crack sample into then slices, get down to atomic size

Question 12

What is the importance of understanding viral structure?

Answer 12

identifying viral cell-receptor interaction
discovery of antivirals
understanding general stable structure
future mutant predictions
determine virus structure

Question 13

What is metastability?

Answer 13

stable and unstable at different times
capsid firm and impenetrable when outside cell
–> protein-protein interactions must not be covalently bonded, would be too hard to break apart

Question 14

What leads to maximum capsid stability?

Answer 14

contacts between identical proteins
small genome limits protein, more efficient

Question 15

What are the characteristics of rod shaped viruses

Answer 15

usually enveloped, subunits are a single repeating protein threaded around nucleic acid
- all helical animal cells are enveloped, have tip

Question 16

Characteristics of icosahedral cells

Answer 16

-20 triangular faces, 12 vertices
3 axis of symmetry, 3 fold, 2 fold and 5 fold

Question 17

What is the simplest icosahedral cell

Answer 17

12 pentamers
parvovirus: 12 capsomeres with 5 proteins

Question 18

What is the advantage of an icosahedral nucleocapsid

Answer 18

the most efficient way to get a symmetrical shell with a max internal volume

Question 19

What is a complex virus

Answer 19

enveloped, pox virus with a brick like structure

Question 20

How is a non enveloped virus used to make a vaccine

Answer 20

express proteins used to make capsid, look like real virus, inject into host, make antibody

Question 21

How might large viruses need to get out of capsid

Answer 21

may need scaffold and protease cleavage event