Lec 4 - Virus structure and function

Question 1

What are structural proteins, when are they made, and provide examples.

Answer 1

Late phase viral proteins involved in shape and structure eg envelope, capsomeres and glycoproteins

Question 2

What are non-structural proteins, when are the made, and provide examples.

Answer 2

Early phase viral proteins involved in replication eg polymerase and integrase

Question 3

What are the 2 functions of structural proteins and what is the term used to describe this state?

Answer 3

Metastable = stable enough to protect the genome but still capable of releasing the genome to infect a cell

Question 4

Describe icosahedral symmetry in terms of the interactions and number of protein subunits.

Answer 4

Icosahedron = 20 triangular faces with 5 triangles along 12 vertices resulting in 5 fold symmetry
Each face has 3 protein subunits so 3x20 faces = 60 subunits

Question 5

What is the T value?

Answer 5

The number of subunits at each face eg 60 subunits with T = 4 means there’s 240 subunits across the entire capsid

Question 6

What virus is an exception to icosahedral symmetry and how?

Answer 6

Poliovirus has a 4th subunit located below the standard 3 subunits on the surface of the capsid

Question 7

What is the term used to describe HIV capsid’s flexibility?

Answer 7

Intrinsically disordered proteins (IDPs) as capsomeres, allowing it to change shape in different environments

Question 8

What do all helical viruses have?

Answer 8

Envelope

Question 9

What is a tegument?

Answer 9

The space between the capsid and envelope filled with proteins associated with immune escape and infectivity

Question 10

What is a viral envelope made of?

Answer 10

Host cell’s lipid bilayer with viral E proteins glycosylated by host cell