viral pathogens I

Question 1

describe structure of the mature HIV-1 particle

Answer 1

The outer envelope of HIV consists of a lipid bilayer with protruding Env spikes (heterotrimers of SU3TM3).
Inside the envelope lie shells of Gag proteins. In the immature particle, Gag itself forms a single shell.
MA associates with the membrane CA forms the conical capsid
NC coats the viral RNA genome.
The core contains two genomic RNA strands (plus strand), tRNALys3, and ~50 copies of each viral enzyme (PR, RT, and IN).

Question 2

genome organisation of retroviruses

Answer 2

Retroviruses synthesise 3 polyproteins:-
Gag; group specific antigen; viral core proteins; MA (matrix),
NC (nucleocapsid)
Pol; viral enzymes; protease (PR), reverse transcriptase (RT) and integrase (IN)
Env; envelope glycoprotein; gp120 SU (surface); gp41 TM (transmembrane)
CA (capsid),

Question 3

HIV-1 regulatory proteins

Answer 3

w Tat - potent activator of viral transcription
w Rev - mediates unspliced RNA nuclear export
w Vif - critical regulator of virus infectivity
w Nef - immune modulator, T-cell activation, virus spread (?) w Vpu - immune modulator, virus release
w Vpr - cell cycle, virus nuclear import (?)

Question 4

what does HIV-1 env consist of

Answer 4

a trimer of gp41 and gp120 peptide subunits and is covered with glycans

Question 5

what does HIV-1 require

Answer 5

two membrane proteins: CD4 and chemokine receptor

HIV 1 = tropic for CD4 expressing cells such as helper T cells and macrophages: the loss of which results in immunodeficiency

Question 6

describe reverse transcriptase

Answer 6

RT is a heterodimer of p66 and p51 subunits.
Catalytic properties are in p66 subunit, p51 serves structural role and lacks RNAse H domain
RT displays three distinct enzymatic activities:
1. RNA-dependent DNA polymerase
2. RNAse H (cleaves RNA from RNA/DNA hybrid) 3. DNA-dependent DNA polymerase

Question 7

what is gag-pol protein generated by

Answer 7

-1 ribosomal frameshifting induced by slippery sequence and RNA hairpin structure

Question 8

what does myristoylation of glycines in MA domain of gag mediate

Answer 8

association with the plasma membrane

Question 9

what does ESCRT machinery hijacking by HIV do

Answer 9

perform membrane abscission during viral release

Question 10

what does gag processing generate

Answer 10

mature virions