Membrane-perturbing domains of HIV type 1 glycoprotein 41

Structural and functional studies were performed to assess the membrane act ions of peptides based on HIV-1 glycoprotein 41,000 (gp41). Previous site-d irected mutagenesis of gp41 has shown that amino acid changes in either the N-terminal fusion or N-leucine zipper region depressed viral infection and syncytium formation, while modifications in the C-leucine zipper domain bo th increased and decreased HIV fusion. Here, synthetic peptides were prepar ed corresponding to the N-terminal fusion region (FP-I; gp41 residues 519-5 41), the nearby N-leucine zipper domain (DP-107; gp41 residues 560-597), an d the C-leucine zipper domain (DP-178; gp41 residues 645-680). With erythro cytes, FP-I or DP-107 induced dose-dependent hemolysis and promoted cell ag gregation; FP-I was more hemolytic than DP-107, but each was equally effect ive in aggregating cells. DP-178 produced neither hemolysis nor aggregation , but blocked either FP-I- or DP-107-induced hemolysis and aggregation. Com bined with previous nuclear magnetic resonance and Fourier transform infrar ed spectroscopic results, circular dichroism (CD) spectroscopy showed that the alpha -helicity for these peptides in solution decreased in the order: DP-107 >> DP-178 > FP- I. CD analysis also indicated binding of DP-178 to e ither DP-107 or FP- I. Consequently, DP-178 may inhibit the membrane action s mediated by either FP-I or DP-107 through direct peptide interactions in solution. These peptide results suggest that the corresponding N-terminal f usion and N-leucine zipper regions participate in HIV infection, by promoti ng membrane perturbations underlying the merging of the viral envelope with the cell surface. Further, the C-leucine zipper domain in "prefusion" HIV may inhibit these membrane activities by interacting with the N-terminal fu sion and N-leucine zipper domains in unactivated gp41. Last, exogenous DP-1 78 may bind to the N-terminal and N-leucine zipper domains of gp41 that bec ome exposed on HIV stimulation, thereby preventing the fusogenic actions of these gp41 regions leading to infection.