View source for CD4

<StructureSection load='2nxy' size='350' side='right' caption='Structure of CD4 (green) complex with antibody light chain (pink), heavy chain (yellow), HIV-1 gp120 (cyan), TRIS and hexane-diol (PDB entry [[2nxy]])' scene='55/551234/Cv/1'>


== Function ==
    
'''CD4''' (or '''Cluster of Differentiation 4''' or '''T cell surface glycoprotein CD4''') is a glycoprotein found on the surface of immune cells.  CD4 has 4 immunoglobulin (Ig) domains (D1-D4), a transmembrane domain and a cytoplasmic tail domain.  D1 and D3 resemble Ig variable domain and D2 and D4 resemble the Ig constant domain.  The D1 domain interacts with class II MHC molecules.  CD4 helps T-cell receptors (TCR) interact with antigen-presenting cells.  The CD4 tail interacts with tyrosine kinase Lck which activates molecular components of the signaling pathway.  

== Relevance ==

HIV-1 binds to CD4 initiating conformation changes in its protein gp120 and allowing the entry of HIV-1 to the host T-cell.<ref>PMID:8493535</ref>
*<scene name='55/551234/Cv/2'>CD4 with antibody and HIV-1 gp120</scene> ([[2nxy]]).<ref>PMID:17301785</ref>

==3D structures of CD4==
[[CD4 3D structures]]

</StructureSection>

== References ==
<references/>
[[Category: Topic Page]]