MoBio Mechanism of HIV Entry into Host Cells Chapter 1

Figure 1-E-3. Structure of the complex formed by HIV gp120, CD4 and an antibody against chemokine receptors. PDB ID = 1GC1.

To enter a host cell, the HIV's surface protein gp120 must interact with two receptors: CD4 and a chemokine receptor (e.g., CCR5). The antibody shown here can block the effects of chemokine receptors. Its position is likely to be the binding site of chemokine receptors in the normal process.

Interaction between gp120 and these two receptors triggers the fusion between viral and host membranes. The detailed mechanism is not entirely clear. It is possible that CD4 and/or chemokine receptors may pull gp120 away, exposing gp41, which is linked to gp120 and embedded in the viral membrane. gp41 is a fusion protein, capable of initiating membrane fusion, thereby allowing the entry of HIV into the host cell.