Lec 4 - assembly, exit and exocytosis Flashcards

1
Q

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

A

proteins are made in massive excess

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2
Q

where are sites of assembly of viruses in a cell

A

internal membranes
provides a means of concentrating protein

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3
Q

where does polio virus assemble

A
  • disassembles the Golgi apparatus
  • produces tubules and vesicles for it to use
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4
Q

what things does host provide for viral assembly

A
  • host cell machinery (some)
  • chaperones
  • cellular transport systems (MT)
  • host secretory pathway
  • host nuclear import and export machinery
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5
Q

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

A
  • signal seq
  • retention seq
  • nuclear localisation seq
  • nuclear export seq
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6
Q

example of assembly from individual protein molecules

A
  • 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
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7
Q

exmaple of assembly from polyprotein protein

A
  • 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)
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8
Q

how is bacteriophage T4 formed

A
  • 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
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9
Q

examples of self assembled viruses

A
  • TMV
  • Polio
  • Haemagglutinin of influenza
  • hep B (surface antigen can form virus like particles)
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10
Q

what are scaffolding proteins

A
  • needed for assisted assembly of more complex proteins
  • TRANSIENT intermediate structures
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11
Q

how are scaffolding porteins transient

A
  • not in the mature virus
  • proteolytic degradation by viral proteases prior to DNA genome entry into capsid
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12
Q

herpes simplex 1

A
  • linear ds DNA
  • memb bound, icosohedral
  • targets mucosal epithelial cells
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13
Q

herpes simplex virus 1:
inital scaffolding protein subunit name

A

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

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14
Q

how is scaffold in herpes simplex 1 dismantles

A

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

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15
Q

what are the scaffolding proteins used for adenovirus

A

L1 52/55

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16
Q

what is sequential assembly

A

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

17
Q

what is concerted assembly

A

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

18
Q

what binds to influenza RNP to target it for assembly

A

M1 protein

19
Q

what does M1 trigger to bind to RNP

A

NEP
this allows it to leave nucleus

20
Q

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

A

influenza envelope proteins
e.g. HA NA and M2

21
Q
A