HIV-1 gp120 envelope glycoprotein complexed with CD4 antigen and an antibody
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The gp120 is also shown bound to an induced neutralizing antibody (17b). At present a wire frame image of the structure of these proteins is shown. You can revert to the original image using the reload button at the end of the bottom-right section of this page.
This structure shows the extracellular part of HIV gp120 (dark blue) bound to the extracellular part of CD4 antigen (light blue) which is located on the surface of a T lymphocyte or macrophage. Also shown is a neutralizing antibody against gp120 (light chain in green and heavy chain in orange). You may want to turn the antibody chains off at this stage using these buttons:
The molecule can be rotated at any time by left clicking the mouse on the molecule and dragging the mouse with the left button depressed, or you can switch on continuous rotation using the buttons at the end of the bottom-right section of this page.
gp120-CD4 antigen interactions
The CD4 antigen on the cell surface and the gp120 of the virus interact via a depression in the gp120 molecule that lacks carbohydrate chains (carbohydrate spacefill ). Direct contacts between the two proteins involve 22 CD4 amino acids and 26 gp120 amino acids but the residues that are most important in this association are Trp427, Glu370, Gly473 and Ile371 of gp120 (spacefill ) that interact with Phe43 of CD4 (spacefill ), and Val430 of gp120 (spacefill ) that interacts with Arg59 of CD4 (spacefill ). Look at the interaction by (and then ). You can also space-fill the individual amino acids and the carbohydrate chains using the buttons at the bottom-right section of this page.
gp120-chemokine receptor interactions
Besides interacting with CD4 antigen on the surface of the T4 cell, gp120 must also interact with a co-receptor. There are many of these chemokine receptors that can interact with gp120. The binding site for the chemokine is induced after the CD4 antigen is bound. This site overlaps with the heavy chain of the antibody in this image (heavy chain spacefill ).The gp120 residues involved in this interaction are Lys121, Arg419, Lys 421 and Gln422 (spacefill ). Notice again, that this interaction also is in a region that lacks carbohydrate chains (spacefill ). You can also space-fill the individual amino acids using the buttons at the bottom-right section of this page.
Now look at the structure of the gp120 molecule in more detail by going here.
© Richard Hunt, University of South Carolina School of Medicine.
Ported to Jmol by Angel Herráez, Universidad de Alcalá, Spain.