Tapasin

TAP-associated glycoprotein, also known as tapasin or TAPBP, is a protein^[5][6] that in humans is encoded by the TAPBP gene.^[7]

TAPBP
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 3F8U
Identifiers
Aliases	TAPBP, NGS17, TAPA, TPN, TPSN, TAP binding protein (tapasin), TAP binding protein
External IDs	OMIM: 601962; MGI: 1201689; HomoloGene: 2401; GeneCards: TAPBP; OMA:TAPBP - orthologs
Gene location (Human) Chr. Chromosome 6 (human)[1] Band 6p21.32 Start 33,299,694 bp[1] End 33,314,254 bp[1]
Gene location (Mouse) Chr. Chromosome 17 (mouse)[2] Band 17 B1|17 17.98 cM Start 34,134,873 bp[2] End 34,148,266 bp[2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in bone marrow cells granulocyte blood spleen mucosa of transverse colon monocyte appendix lymph node epithelium of colon right adrenal gland Top expressed in mesenteric lymph nodes Ileal epithelium subcutaneous adipose tissue blood stroma of bone marrow right lung spleen right lung lobe pituitary gland submandibular gland More reference expression data BioGPS More reference expression data
Gene ontology Molecular function peptide antigen binding TAP2 binding unfolded protein binding ABC-type peptide antigen transporter activity protein binding MHC class I protein binding TAP1 binding TAP complex binding Cellular component integral component of membrane endoplasmic reticulum membrane membrane Golgi membrane TAP complex MHC class I peptide loading complex endoplasmic reticulum integral component of lumenal side of endoplasmic reticulum membrane phagocytic vesicle membrane endoplasmic reticulum-Golgi intermediate compartment membrane Biological process retrograde vesicle-mediated transport, Golgi to endoplasmic reticulum antigen processing and presentation of peptide antigen via MHC class I antigen processing and presentation of endogenous peptide antigen via MHC class I regulation of protein complex stability immune response peptide antigen stabilization regulation of gene expression antigen processing and presentation of exogenous peptide antigen via MHC class I, TAP-dependent vesicle fusion with endoplasmic reticulum-Golgi intermediate compartment (ERGIC) membrane amide transport protein-containing complex assembly MHC class Ib protein complex assembly peptide transport Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 6892 21356 Ensembl ENSG00000231925 ENSG00000236490 ENSG00000206281 ENSG00000206208 ENSG00000112493 n/a ENSMUSG00000024308 UniProt O15533 Q9R233 RefSeq (mRNA) NM_003190 NM_172208 NM_172209 NM_001025313 NM_009318 RefSeq (protein) NP_003181 NP_757345 NP_757346 NP_001020484 NP_033344 Location (UCSC) Chr 6: 33.3 – 33.31 Mb Chr 17: 34.13 – 34.15 Mb PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Function

The TAPBP gene encodes a transmembrane glycoprotein that mediates interaction between newly assembled major histocompatibility complex (MHC) class I molecules and the transporter associated with antigen processing (TAP), which is required for the transport of antigenic peptides across the endoplasmic reticulum membrane. This interaction facilitates optimal peptide loading on the MHC class I molecule. Up to four complexes of MHC class I and tapasin may be bound to a single TAP molecule. Tapasin contains a C-terminal double-lysine motif (KKKAE) known to maintain membrane proteins in the endoplasmic reticulum. In humans, the tapasin gene lies within the major histocompatibility complex on chromosome 6. Alternative splicing results in three transcript variants encoding different isoforms.^[7]

Tapasin is a MHC class I antigen-processing molecule present in the lumen of the endoplasmic reticulum. It plays an important role in the maturation of MHC class I molecules in the ER lumen. Tapasin is one component of the peptide-loading complex, and can be found associated with MHC class I molecules after the MHC class I heavy chain has associated with Beta₂ microglobulin. The peptide-loading complex consists of TAP, tapasin, MHC class I, calreticulin, and ERp57. Tapasin recruits MHC class I molecules to the TAP peptide transporter, and also enhances loading of MHC class I with high-affinity peptides. Following loading of MHC class I with a high-affinity ligand, the interaction between tapasin and MHC class I disappears.^[8]

Interactions

Tapasin has been shown to interact with:

• HLA-A,^[9] and
• TAP1^[9][10]

See also

• Transporter associated with antigen processing ("TAP")