Lecture 4

Question 1

What provides the basis for viral assembly?

Answer 1

Viral symmetry

Question 2

What are the two rules of viral symmetry?

Answer 2

1. Each subunit makes identical contacts with neighbouring subunits
2. Bonds between subunits are non-covalent (weaker) interactions

Question 3

What virus has helical symmetry?

Answer 3

The tobacco mosaic virus

Question 4

What virus has polyhedral symmetry?

Answer 4

Simoan

Question 5

For polyhedral viruses to maintain round symmetry despite irregular protein shapes, they must have a defined number of proteins. What numbers are possible?

Answer 5

60, 180, 240, 960

Question 6

In an icosahedron, where are the axes of symmetry?

Answer 6

Vertice: 5-fold symmetry

Face of trimer: 3-fold symmetry

Edge: 2-fold symmetry

Question 7

How many subunits are there in the Norwalk virus? Why isn’t it a perfectly symmetrical icosahedron?

Answer 7

180, it is a quasiequivalent icosahedron, which means that it tends to begin to lost the 5-fold axis of symmetry as some trimers form 6-fold vertices.

Question 8

What method was used to obtain this image?

Answer 8

Cryo electron microscopy

Question 9

How was this image obtained?

Answer 9

Through the use of NMR spectroscopy

Question 10

How was this image obtained?

Answer 10

Electron microscopy

Question 11

How was this image obtained?

Answer 11

X-ray crystallography

Question 12

How was this image obtained?

Answer 12

Cryo EM