ABSTRACT The gp41 subunit of the HIV envelope glycoprotein plays a major role in the fusion of viral and target cell membranes, thereby releasing viral genetic material into the cell and initiating virus infection. The extracellular region of gp41 consists of two heptad repeat (HR) regions containing hydrophobic sequences with high α-helical propensity: one is located adjacent to the N-terminal fusion peptide (NHR); the other at the C-terminus of gp41 ectodomain (CHR). The peptides derived from the CHR regions of gp41, designated C-peptides, have potent inhibitory activity on the membrane fusion step of HIV-1 infection. Biochemical and biophysical studies suggest that in the fusion-active state, the CHR region reacts with the NHR region of gp41 to form a six-helix bundle, consisting of three N-terminal and three C-terminal helices packed in the reverse direction and representing the fusion-active gp41 core structure. A conserved, hydrophobic, deep cavity on the surface of the central coiled coil within gp41 core plays an important role in membrane fusion, making it an attractive target for the development of anti-HIV drugs. So far, three different strategies have been developed for identification of small molecular HIV-1 inhibitors targeted to the HIV-1 gp41 core, especially to the hydrophobic cavity. This review will summarize the studies on the C-peptide inhibitors, the characterization of the HIV-1 gp41 core structure and the latest development in discovering HIV-1 entry inhibitors. It is expected that novel antiviral drugs targeted to the HIV-1 gp41 core will be developed in the near future for the chemotherapy and/or prophylaxis of HIV-1 infection and AIDS.
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