Tapasin; TPN; TPSN; NGS-17; TAP-associated protein; TAP-binding protein (TAPBP, NGS17, TAPA)

Function

• role in the association of MHC class I with transporter associated with antigen processing (TAP)
• role in assembly of MHC class I with peptide (peptide loading)
• heterodimer with PDIA3; disulfide-linked
• interacts with TAP1, thus a subunit of the TAP complex, also known as the peptide loading complex (PLC)
• interaction with TAP1 is TAP2-independent & is required for efficient peptide-TAP interaction
• obligatory mediator for the interaction between newly assembled MHC class I molecules, clareticulin, PDIA3 & TAP
• up to 4 MHC class I/tapasin complexes bind to 1 TAP

Structure

• the N-terminus is required for efficient association with MHC class I molecule & for a stable interaction between MHC class I & calreticulin.
• binding to TAP is mediated by the C-terminus region
• contains 1 Ig-like C1-type (immunoglobulin-like) domain

Compartment

• endoplasmic reticulum membrane
• single-pass type 1 membrane protein (probable)

Alternative splicing

• named isoforms=3
• at leas some isoforms due to a partial intron retention

Expression

• expressed in neutrophils, mostly in fully differentiated cells

Polymorphism

• the 2 alleles of TAPBP; TAPBP*01 (Tapasin*01) & TAPBP*02 (Tapasin*02); are in linkage disequilibria with the HLA-DRB1 locus in a Japanese population

More general terms

• immunoglobulin superfamily protein
• protein subunit
• phosphoprotein
• membrane protein

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=6892
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:6892
• OMIM: https://mirror.omim.org/entry/601962
• UniProt: http://www.uniprot.org/uniprot/O15533.html