T-cell surface glycoprotein CD4 (T-cell surface antigen T4/Leu-3) (CD antigen CD4)
1_MNRGV 6_ PFRHL 11_ LLVLQ 16_ LALLP 21_ AATQG 26_ KKVVL 31_ GKKGD 36_ TVELT 41_ CTASQ 46_ KKSIQ 51_ FHWKN 56_ SNQIK 61_ ILGNQ 66_ GSFLT 71_ KGPSK 76_ LNDRA 81_ DSRRS 86_ LWDQG 91_ NFPLI 96_ IKNLK 101_ IEDSD 106_ TYICE 111_ VEDQK 116_ EEVQL 121_ LVFGL 126_ TANSD 131_ THLLQ 136_ GQSLT 141_ LTLES 146_ PPGSS 151_ PSVQC 156_ RSPRG 161_ KNIQG 166_ GKTLS 171_ VSQLE 176_ LQDSG 181_ TWTCT 186_ VLQNQ 191_ KKVEF 196_ KIDIV 201_ VLAFQ 206_ KASSI 211_ VYKKE 216_ GEQVE 221_ FSFPL 226_ AFTVE 231_ KLTGS 236_ GELWW 241_ QAERA 246_ SSSKS 251_ WITFD 256_ LKNKE 261_ VSVKR 266_ VTQDP 271_ KLQMG 276_ KKLPL 281_ HLTLP 286_ QALPQ 291_ YAGSG 296_ NLTLA 301_ LEAKT 306_ GKLHQ 311_ EVNLV 316_ VMRAT 321_ QLQKN 326_ LTCEV 331_ WGPTS 336_ PKLML 341_ SLKLE 346_ NKEAK 351_ VSKRE 356_ KAVWV 361_ LNPEA 366_ GMWQC 371_ LLSDS 376_ GQVLL 381_ ESNIK 386_ VLPTW 391_ STPVQ 396_ PMALI 401_ VLGGV 406_ AGLLL 411_ FIGLG 416_ IFFCV 421_ RCRHR 426_ RRQAE 431_ RMSQI 436_ KRLLS 441_ EKKTC 446_ QCPHR 451_FQKTC
1: Integral membrane glycoprotein that plays an essential role in the immune response and serves multiple functions in responses against both external and internal offenses. In T-cells, functions primarily as a coreceptor for MHC class II molecule:peptide complex. The antigens presented by class II peptides are derived from extracellular proteins while class I peptides are derived from cytosolic proteins. Interacts simultaneously with the T-cell receptor (TCR) and the MHC class II presented by antigen presenting cells (APCs). In turn, recruits the Src kinase LCK to the vicinity of the TCR-CD3 complex. LCK then initiates different intracellular signaling pathways by phosphorylating various substrates ultimately leading to lymphokine production, motility, adhesion and activation of T-helper cells. In other cells such as macrophages or NK cells, plays a role in differentiation/activation, cytokine expression and cell migration in a TCR/LCK-independent pathway. Participates in the development of T-helper cells in the thymus and triggers the differentiation of monocytes into functional mature macrophages
2: (Microbial infection) Primary receptor for human immunodeficiency virus-1 (HIV-1) (PubMed:12089508, PubMed:16331979, PubMed:2214026, PubMed:9641677). Down-regulated by HIV-1 Vpu (PubMed:17346169). Acts as a receptor for Human Herpes virus 7/HHV-7 (PubMed:7909607)