Biology Reference
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Fig. 4.
Linear map of HIV Env (SF162) indicating various conserved and
variable domains (Panel A), and large numbers of cysteine residues and
extensive glycosylation, likely conformation of Env involving gp120
ectodomain, and gp41 on the surface of the virus (Panel B). Also shown is
the schematic of trimers in open and closed confirmation (Panel C). Further
structural studies will be needed to demonstrate if the native trimers are in
open or closed conformation.
domain termed gp120 (Fig. 4A). Env proteins become heavily glyco-
sylated during their passage through the Golgi apparatus. gp120 and
gp41 are non-covalently associated on the viral surface to form
trimeric spikes (Fig. 4B) that can bind to the CD4 on T-cells, which
is the primary receptor of HIV-1. Comparison of the sequences of the
env
gene from different isolates and clades reveals that it has five
hypervariable regions and five conserved regions, and a large number
of cysteine residues (Fig. 4A). There are differences between the size
of the variable loops and the number of glycosylation sites in V1 and
V2 loops among virus isolates of different clades, and between early
and late primary viruses. This sequence variation in the hypervariable
loops is due to nucleotide changes and subsequent accumulation of
point mutations resulting in amino acid substitutions. These muta-
tion-induced changes in Env tertiary structure are selected by the
