A salt bridge between an N-terminal coiled coil of gp41 and an antiviral agent targeted to the gp41 core is important for anti-HIV-1 activity

HIV-1 envelope glycoprotein transmembrane subunit gp41 play a critical role in the fusion of viral and target cell membranes. The gp41 C-terminal heptad repeat region interacts with the N-terminal coiled-coil region to form a six-stranded core structure. Peptides derived from gp41 C-terminal heptad repeat region (C-peptides) are potent HIV-1 entry inhibitors by binding to gp41 N-terminal coiled-coil region. Most recently, we have identified two small organic compounds that inhibit HIV-1-mediated membrane fusion by blocking the formation of gp41 core. These two active compounds contain both hydrophobic and acidic groups while the inactive compounds only have hydrophobic groups. Analysis by computer modeling indicate that the acidic groups in the active compounds can form salt bridge with Lys 574 in the N-terminal coiled-coil region of gp41. Asp 632 in a C-peptide can also form a salt bridge with Lys 574. Replacement of Asp 632 with positively charged residues or hydrophobic residues resulted in significant decrease of HIV-1 inhibitory activity. These results suggest that a salt bridge between an N-terminal coiled coil of the gp41 and an antiviral agent targeted to the gp41 core is important for anti-HIV-1 activity.