CD4 (or Cluster of Differentiation 4) is a glycoprotein found on the surface of immune cells. CD4 has 4 immunoglobulin (Ig) domains, 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. HIV-1 binds to CD4 initiating conformation changes in its protein gp120 and allowing the entry of HIV-1 to the host T-cell.
3D structures of CD4
Updated on 25-August-2014
CD4 domains
1cid – rCD4 D3 and D4 domains - rat
3cd4, 1cdh, 1cdi, 1cdj – hCD4 D1 and D2 domains - human
1cdu, 1cdy – hCD4 D1 and D2 domains (mutant)
1wio, 1wip, 1wiq – hCD4 D1, D2, D3 and D4 domains
2klu – hCD4 transmembrane and tail domains - NMR
CD4 binary complex
1q68 – hCD4 tail + Lck peptide - NMR
3b71 – hCD4 tail + focal adhesion kinase 1
3o2d – hCD4 D1 and D2 domains + antibody
CD4 ternary complex
1gc1, 1g9m, 1g9n, 1rzj, 1rzk, 2b4c, 2nxy, 2nxz, 2ny0, 2ny1, 2ny2, 2ny3, 2ny4, 2ny5, 2ny6, 3jwd, 3jwo, 4jm2 – hCD4 D1 and D2 domains + antibody + gp120
2qad, 3lqa – hCD4 D1 and D2 domains + antibody + gp160
1jl4 – hCD4 D1 and D2 domains + class II MHC + ovotransferin peptide
3s4s – hCD4 D1 and D2 domains + class II MHC + haemaglutinin peptide
3s5l – hCD4 D1 and D2 domains + class II MHC + HA peptide
3t0e – hCD4 D1 and D2 domains + class II MHC + TCR
