The envelope glycoprotein gp160 of HIV-1 is consisted of two subunits, gp120 and gp41. The gp120 binds the CD4 receptor and the co-receptor CCR5 or CXCR4 on the cell membrane. The binding triggers a fusion of cell membrane with the viral envelope, allowing the entry of viral gene and proteins into the infected cell.

Gp41 is the key protein for the fusion process. For the reason, gp41 is also called fusion protein. Almost all HIV-1 proteins have highly mutation rates, which makes it extremely difficult to develop drugs targeting them. On the contrast, the active site of gp41 is very conservative that rarely mutates. The conservative structure and its critical function in the HIV-1 fusion process make the gp41 protein an ideal drug target, and an extremely hot research area in HIV-1 studies.