HIV-1 envelope glycoprotein gp160 is a pre-protein that is cleaved
in the host Golgi to produce two proteins: gp120 and gp41.
Surface protein gp120 is the viral protein that binds the host CD4
receptor. Binding to CD4 causes a structural conformation change
allowing for a high affinity binding site to be formed for CXCR4
and/or CCR5. The protein is often present as a trimer, has five
variable domains and post-translational modifications
(glycosylation to evade host immune recognition).
Transmembrane protein gp41 is associated with gp120 and makes up
the 'stalk' the envelope spike. The protein is required for viral
fusion with the host cell. The protein is roughly 345 amino acids
in size with three domains: C-terminal cytoplasmic tail,
transmembrane domain and extracellular domain (to associate with