| 内容提要: |
Programmed cell death-1 (PD-1) is an immunoreceptor belonging to the CD28/CTLA-4 superfamily that delivers negative signals and suppresses immune responses against autoantigens and tumors upon interaction with its two ligands, PD-L1 or PD-L2. The inhibitory signals of PD-1 are mediated by the SHP-2 phosphatase, which is recruited to the phosphorylated Tyr residue in the immuno-tyrosine based switch motif of the cytoplasmic tail of PD-1 and dephosphorylates signal transducers of the TCR or BCR pathways. PD-1 is type I transmembrane glycoproteins composed of an Ig Variable-type extracellular domain (V domain), a transmembrane domain, and a cytoplasmic tail responsible for the binding of signaling and scaffolding molecules. Like anti TCRs, the FG loop of PD-1 is centrally located and the other loops are outwards from the center so we get the PD-1-PD-L1 complex structure from Protein Data Bank (PDB) to analyse whether the FG loop is necessary and dominating to binding site. Using Chimera on computer to filtrate residues located on PD-1 FG loop which are less than 5Å distance from ligand loop simultaneously have relationship with ligation probably, We find there are approximately 10 residues located on FG loop in this distance range. What’s more, the binding data of PD-1-PD-L1 complex structure from reference tell us FG loop make more contribution to ligation actually. |