TAP complex (MHC class 1 peptide loading complex)

Function: - pump which delivers peptides to class 1 MHC molecules within the endoplasmic reticulum of antigen presenting cells - role in the transport of antigens from the cytoplasm to the endoplasmic reticulum for association with MHC class 1 molecules - acts as a molecular scaffold for final stage of MHC class 1 folding, binding of peptide - nascent MHC class 1 molecules associate with TAP via tapasin - inhibited by covalent attachment of herpes simplex virus ICP47 protein, which blocks peptide-binding site of TAP - inhibited by human cytomegalovirus US6 glycoprotein, which binds to the lumenal side of the TAP complex & inhibits peptide translocation by specifically blocking ATP-binding to TAP1 & prevents the conformational rearrangement of TAP induced by peptide binding - inhibited by human adenovirus E3-19K glycoprotein, which binds the TAP complex & acts as a tapasin inhibitor, preventing MHC class 1/TAP association - heterodimer of TAP1 & TAP2 Structure: - heterodimer of TAP1 & TAP2 - peptide-binding site is shared between the cytoplasmic loops of TAP1 & TAP2 Compartment: endoplasmic reticulum

Properties

SUBUNITS: antigen peptide transporter-1 COMPARTMENT: endoplasmic reticulum MOTIF: cytoplasmic domain {1-15} transmembrane domain {16-36} exoplasmic loop {37-53} transmembrane domain {54-76} cytoplasmic loop {77-92} transmembrane domain {93-113} exoplasmic loop {114-133} transmembrane domain {134-154} cytoplasmic loop {155-186} transmembrane domain {187-207} exoplasmic loop {208-227} transmembrane domain {228-248} cytoplasmic loop {249-298} transmembrane domain {299-319} exoplasmic loop {320-328} transmembrane domain {329-349} cytoplasmic loop {350-418} MOTIF: binding site SITE: 375-420 FOR-BINDING-OF: peptide transmembrane domain {419-439} exoplasmic loop {440-443} transmembrane domain {444-464} MOTIF: binding site SITE: 453-464 FOR-BINDING-OF: peptide cytoplasmic domain {465-748} MOTIF: binding site SITE: 465-487 FOR-BINDING-OF: peptide ABC transporter {503-742} ATP-binding site NAME: ATP-binding site SITE: 538-545 antigen peptide transporter-2 COMPARTMENT: endoplasmic reticulum MOTIF: exoplasmic domain {1-6} transmembrane domain {7-27} cytoplasmic loop {28-56} transmembrane domain {57-77} exoplasmic loop {78-98} transmembrane domain {99-119} cytoplasmic loop {120-148} transmembrane domain {149-169} exoplasmic loop {170-187} transmembrane domain {188-208} cytoplasmic loop {209-266} transmembrane domain {267-287} exoplasmic loop {288-293} transmembrane domain {294-314} cytoplasmic loop {315-374} MOTIF: binding site SITE: 301-389 FOR-BINDING-OF: peptide transmembrane domain {375-395} exoplasmic loop {396-408} transmembrane domain {409-429} cytoplasmic domain {430-686} MOTIF: binding site SITE: 414-433 FOR-BINDING-OF: peptide ABC transporter {468-686} ATP-binding site NAME: ATP-binding site SITE: 503-510

References

UniProt :accession O75081

Components

antigen peptide transporter-2 (APT2), peptide transporter TAP2, peptide transporter PSF2, peptide supply factor 2 (PSF-2), RING11, Y1, PSF2, MTP-2 or HAM-2 Transporter Associated with Antigen Processing; antigen peptide transporter-1; peptide transporter TAP1, peptide transporter PSF1, peptide supply factor 1; PSF-1 (TAP1, APT1, RING4, Y3, MTP-1, HAM-1)