Characterization of the Interaction of Two Peptides from the N Terminus of the NHR Domain of HIV-1 gp41 with Phospholipid Membranes

Abstract

The HIV-1 gp41 envelope glycoprotein is responsible for the membrane fusion between the virus and the target cell. According to recent models, the N-terminal coiled-coil (NHR) region of gp41 is involved in forming the interfaces between neighboring helices in the six-helix bundle, as well as in membrane binding and perturbation. In order to get new insights into the viral membrane fusion mechanism, two peptides, pFP15 and pFP23, pertaining to the first part of the gp41 NHR domain were studied regarding their structure and their ability to induce membrane leakage, aggregation, and fusion, as well as their affinity toward specific phospholipids by a variety of spectroscopic methods. Our results demonstrate that the first part of the NHR domain interacts with negatively charged phospholipid-containing model membranes, modifies the phase behavior of membrane phospholipids, and induces leakage and aggregation of liposomes, suggesting that it could be involved directly in the merging of the viral and target cell membranes working synergistically with other membrane-active regions of the gp41 glycoprotein to boost the fusion process. On the other hand, we suggest that this region of the NHR domain could be involved in the first steps of the destabilization of the HIV-1 gp41 six-helix bundle after its interaction with negatively charged phospholipid headgroups.

Identification of the Membrane-active Regions of Hepatitis C Virus p7 Protein

“…Excitation and emission slits were set at 10 nm. The proportion of labeled and unlabeled vesicles, lipid concentration, and other experimental and measurement conditions were the same as indicated previously (31).…”

“…Intensity values were corrected for dilution, and the scatter contribution was derived from lipid titration of a vesicle blank. The data were analyzed as previously described (31).…”

“…The steady-state fluorescence anisotropy, ͗r͘, was measured with an automated polarization accessory using a Varian Cary Eclipse fluorescence spectrometer, coupled to a Peltier device (Varian) for automatic temperature change. The data were analyzed as previously described (31).…”

“…After each addition an incubation period of 15 min was kept before the measurement. The data were analyzed as previously described (31).…”

Behaviour of a peptide sequence from the GB virus C/hepatitis G virus E2 protein in Langmuir monolayers: Its interaction with phospholipid membrane models

“…These enveloped viruses, i.e., HIV and GBV-C/HGV, infect host cells by fusing their envelope with the external cellular membrane [12,13]. It is known that in eukaryotes, this process is mediated by viral proteins, which help the virus introduce its genetic material into the host cells [14,15].…”