Lec 4 - assembly, exit and exocytosis

Question 1

how do viruses ensure the proteins find each other to assemble in cellular environemnt

Answer 1

proteins are made in massive excess

Question 2

where are sites of assembly of viruses in a cell

Answer 2

internal membranes
provides a means of concentrating protein

Question 3

where does polio virus assemble

Answer 3

• disassembles the Golgi apparatus
• produces tubules and vesicles for it to use

Question 4

what things does host provide for viral assembly

Answer 4

• host cell machinery (some)
• chaperones
• cellular transport systems (MT)
• host secretory pathway
• host nuclear import and export machinery

Question 5

4 types of AA sequences viral proteins have to ensure correct localisation

Answer 5

• signal seq
• retention seq
• nuclear localisation seq
• nuclear export seq

Question 6

example of assembly from individual protein molecules

Answer 6

• simian virus 40
• only 2 types of proteins made
• one central and 5 units to form the entamer
• correct stoichiometry needed when proteins being made

Question 7

exmaple of assembly from polyprotein protein

Answer 7

• poliovirus
• all 4 proteins it needs to form a unit are translated as ONE protein
• otherwise impossible to find each other
• when its folded, the links get cleaved
• and forms a unit
  (no issues with stoichiometry)

Question 8

how is bacteriophage T4 formed

Answer 8

• assembly ine, ordely fasion
• allows assembly of the more complex viruses
• discreet intermediate structures made
• wont proceed unless previous structure formed
• head, tail, tail fibres
• then assembled

Question 9

examples of self assembled viruses

Answer 9

• TMV
• Polio
• Haemagglutinin of influenza
• hep B (surface antigen can form virus like particles)

Question 10

what are scaffolding proteins

Answer 10

• needed for assisted assembly of more complex proteins
• TRANSIENT intermediate structures

Question 11

how are scaffolding porteins transient

Answer 11

• not in the mature virus
• proteolytic degradation by viral proteases prior to DNA genome entry into capsid

Question 12

herpes simplex 1

Answer 12

• linear ds DNA
• memb bound, icosohedral
• targets mucosal epithelial cells

Question 13

herpes simplex virus 1:
inital scaffolding protein subunit name

Answer 13

> pre-VP22a
stimulates binding of VP5 structural protein
and Vp23 and VP19C triplexes
VP5, VP23 and VP19C are part of mature virus

Question 14

how is scaffold in herpes simplex 1 dismantles

Answer 14

VP24 protease
- cleaves c terminal sequences from the scaffolding protein
- degrades scaffolding proteins
- conformational change = VP5 hexamers and pentamers tightly associate AND dna genome can enter via UL6 portal

Question 15

what are the scaffolding proteins used for adenovirus

Answer 15

L1 52/55

Question 16

what is sequential assembly

Answer 16

genome is inserted into a pre-formed protein shell
e.g. herpes simplex, adenovirus;

Question 17

what is concerted assembly

Answer 17

structural subunits only assemble when nucleic acid is present
e.g. TMV, influenza, measles, polio

Question 18

what binds to influenza RNP to target it for assembly

Answer 18

M1 protein

Question 19

what does M1 trigger to bind to RNP

Answer 19

NEP
this allows it to leave nucleus

Question 20

what is at the plasma memb that the M1-RNP complex interacts with

Answer 20

influenza envelope proteins
e.g. HA NA and M2