Propensity for a leucine zipper-like domain of human immunodeficiency virus type 1 gp41 to form oligomers correlates with a role in virus-induced fusion rather than assembly of the glycoprotein complex.

Abstract

For a number of viruses, oligomerization is a critical component of envelope processing and surface expression. Previously, we reported that a synthetic peptide (DP-107) corresponding to the putative leucine zipper region (aa 553-590) of the transmembrane protein (gp4l) of human immunodeficiency virus type 1 (HIV-1) exhibited a-helical secondary structure and self-associated as a coiled coil. In view of the tendency of this type of structure to mediate protein association, we speculated that this region of gp4l might play a role in HIV-1 envelope oligomerization. However, later it was shown that mutations which should disrupt the structural elements of this region of gp4l did not affect envelope processing, transport, or surface expression (assembly oligomerization). In this report we compare the effects of amino acid substitutions within this coiled-coil region on structure and function of both viral envelope proteins and the corresponding synthetic peptides. Our results establish a correlation between the destabilizing effects of amino acid substitutions on coiledcoil structure in the peptide model and phenotype of virus entry. These biological and physical biochemical studies do not support a role for the coiled-coil structure in mediating the assembly oligomerization of HIV-1 envelope but do imply that this region of gp4l plays a key role in the sequence of events associated with viral entry. We propose a functional role for the coiled-coil domain of HIV-1 gp4l.

A Discrete Stage of Baculovirus GP64-mediated Membrane Fusion

“…Single leucine-to-alanine mutations of the F proteins from paramyxoviruses do not block fusion, but multiple leucine-to-alanine mutations do abolish fusion activity of the protein but do not negatively affect F protein oligomerization or cell surface expression (Buckland et al, 1992;Sergel-Germano et al, 1994;Reitter et al, 1995). Nonconservative mutagenesis of the heptad repeat of HIV blocks cell-to-cell fusion and viral infectivity but does not affect oligomerization or cell surface transport of the GP120-GP41 protein (Dubay et al, 1992;Wild et al, 1994a;Chen et al, 1995).…”

“…Single leucine-to-alanine mutations of the F proteins from paramyxoviruses do not block fusion, but multiple leucine-to-alanine mutations do abolish fusion activity of the protein but do not negatively affect F protein oligomerization or cell surface expression (Buckland et al, 1992;Sergel-Germano et al, 1994;Reitter et al, 1995). Nonconservative mutagenesis of the heptad repeat of HIV blocks cell-to-cell fusion and viral infectivity but does not affect oligomerization or cell surface transport of the GP120-GP41 protein (Dubay et al, 1992;Wild et al, 1994a;Chen et al, 1995).Short peptides containing hydrophobic 4-3 heptad repeats (leucine zipper-like motifs) are potent inhibitors of syncytia formation and viral infection. Examples include peptides derived from envelope proteins of HIV (Wild et al, , 1994b Jiang et al, 1993a,b;Judice et al, 1997) and paramyxoviruses (Rapaport et al, 1995;Lambert et al, 1996;Yao and Compans, 1996;Ghosh et al, 1997;Wild and Buckland, 1997;Young et al, 1997;Ben-Efraim et al, 1999).…”

Biochemical and Biological Characterization of a Dodecameric CD4-Ig Fusion Protein

“…Because sCD4-gp120 ligation involves slow binding kinetics and substantial changes in entropy, gp120 avidity effects strongly favor membrane-associated receptors (25). 2 Second, sCD4-gp120 ligation promotes a high affinity interaction between gp120 and CCR5 (26 -29), thus further increasing the apparent affinity of gp120 for the plasma membrane.…”

Multimerization Potential of the Cytoplasmic Domain of the Human Immunodeficiency Virus Type 1 Transmembrane Glycoprotein gp41

“…This region overlaps a highly conserved leucine zipper-like heptad repeat sequence adjacent to the N-terminal fusion peptide sequence. The leucine zipper-like motif plays a crucial role in viral infectivity and membrane fusion (5)(6)(7)(8). The six-stranded coiled-coil structure, formed by the leucine zipper-like motif and the C-terminal ␣-helix located in the ectodomain of gp41 and proximal to the TM domain, represents a fusion active conformation of the TM core (9 -11).…”