Investigation of Human Immunodeficiency Virus Fusion Peptides. Analysis of Interrelations Between Their Structure and Function

Abstract

The N-terminal region of the human immunodeficiency virus type 1 (HIV-1) gp41 appears to be involved in virus-cell membrane fusion. To study the influence of fusion domain structure on gp41 interaction with artificial lipid membranes, two families of peptides were synthesized. The peptides of the first family starting from the C-terminal Gly-532 of gp160 (BRU isolate) were assembled in a stepwise manner to N-terminus of gp41(Ala-517). These hydrophobic peptides, containing 10-16 amino acid residues (a.a.), were able to form channel-like current fluctuation through planar lipid membranes, and the longest 15-16 a.a. peptides lysed the liposomes. Peptides of the second family beginning from the C-terminal Arg-538 and continuing to Val-510 contained several hydrophilic amino acid residues. These 15-22 a.a. peptides also increased the conductance of planar lipid bilayers and lysed liposomes. The degree of liposome lysis depended upon peptide length and concentration. The attachment of gp120 C-terminal amino acid or peptides to N-terminus of 517-538 peptide resulted in complete loss of activity. The effects of the second family of peptides on membranes were reduced to a great extent at acidic pH. The conjugation of 22 a.a. Lys peptide with bovine serum albumin decreased its lytic activity. The circular dichroism study of these peptides revealed alpha-helix configuration in hydrophobic and aqueous media only for deca- and longer peptides. The electron microscopy of 22 a.a. peptide performed in the aqueous medium showed large spherical aggregates about 0.5-0.7 micron in diameter consisting of long filaments approximately 5 nm in diameter. Other tested peptides could generate only short strings. Thus, the effects of fusion peptides on lipid membranes depends on their sequence and length, secondary and tertiary structures, and freedom of their N-terminus.

Liposome destabilization induced by the HIV‐1 fusion peptide Effect of a single amino acid substitution

“…Rafalski et al [6] showed destabilization of POPG liposomes and membrane mixing of small sonicated vesicles. Slepushkin et al [7] showed the ability of a family of gp41 peptides to cause increased conductance of planar lipid bilayers, liposome lysis and lipid mixing. The HIV-1 fusion peptide has been shown to induce lysis of human erythrocytes and CD4 ÷ lymphocytes [8].…”

Membrane Interface-Interacting Sequences within the Ectodomain of the Human Immunodeficiency Virus Type 1 Envelope Glycoprotein: Putative Role during Viral Fusion

“…The fusion peptide is likely to insert into the target lipid bilayer, making gp41 capable of interacting simultaneously with the viral and cell membranes (5,8,12,13,25,39). The involvement of this conserved hydrophobic segment of about 25 amino acids in triggering fusion is supported by prediction (13,15,40), mutational analysis (2,10,11,35), and in vitro studies carried out using synthetic peptides and model membranes (16,20,23,(27)(28)(29)(30)(31)36). Fusion peptides inserted into the target membrane might drive the aggregation of gp41 trimers at initial sites of fusion as well (39).…”

Characterization of the HIV N-terminal Fusion Peptide-containing Region in Context of Key gp41 Fusion Conformations

“…Our present understanding of FP structure and function is based on FP-containing fragments amenable to chemical synthesis. The tendency of free FP-containing fragments to aggregate in solution is well documented (17)(18)(19)(20)(21). However, their highly hydrophobic nature suggests they target or interact with membranes.…”