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Literature summary for 7.4.2.14 extracted from
- Critical role for the tapasin-docking site of TAP2 in the functional integrity of the MHC class I-peptide-loading complex (2005), J. Immunol., 175, 5104-5114 .
Cloned(Commentary)
| Cloned (Comment) | Organism |
|---|---|
| genes tap1 and tap2, recombinant coexpression of wild-type and mutant TAP1 and TAP2 subunits in human TAP-deficient T2 cells | Rattus norvegicus |
Protein Variants
| Protein Variants | Comment | Organism |
|---|---|---|
| additional information | generation of N-terminally truncated variants of TAP1 and TAP2 in combination with wild-type chains, as fusion proteins or as single subunits (TAP1-2DELTAN, and 2-1DELTAN. In the case of TD1/2DELTAN and TD1DELTAN/2DELTAN). TAP variants lacking the N domain in TAP2, but not in TAP1, form PLCs that are disturbed in the physical interaction with calreticulin (Crt), calnexin (Cnx), and ER60 and the quality control of MHC I loading. Head-to-tail-fusion of TAP chains allows stable expression of transporters lacking both N domains | Rattus norvegicus |
General Stability
| General Stability | Organism |
|---|---|
| tapasin stabilizes the enzyme, three tapasin docking sites in TAP cooperate to facilitate transporter stabilization and heterodimerization | Rattus norvegicus |
Localization
| Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|
| endoplasmic reticulum membrane | - |
Rattus norvegicus | 5789 | - |
Metals/Ions
| Metals/Ions | Comment | Organism | Structure |
|---|---|---|---|
| Mg2+ | required | Rattus norvegicus |  |
Natural Substrates/ Products (Substrates)
| Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| ATP + H2O + antigen peptide[side 1] | Rattus norvegicus | - |
ADP + phosphate + antigen peptide[side 2] | - |
? | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Rattus norvegicus | P36370 AND P36372 | subunits TAP1 and TAP2 | - |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| ATP + H2O + antigen peptide[side 1] | - |
Rattus norvegicus | ADP + phosphate + antigen peptide[side 2] | - |
? | |
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| TAP | - |
Rattus norvegicus |
| TAP1 | - |
Rattus norvegicus |
| TAP2 | - |
Rattus norvegicus |
Cofactor
| Cofactor | Comment | Organism | Structure |
|---|---|---|---|
| ATP | - |
Rattus norvegicus | |
General Information
| General Information | Comment | Organism |
|---|---|---|
| malfunction | TAP variants lacking the N domain in TAP2, but not in TAP1, build PLCs that fail to generate stable MHC I-peptide complexes. This correlates with a substantially reduced recruitment of accessory chaperones into the PLC demonstrating their important role in the quality control of MHC I loading. stable surface expression of MHC I can be rescued in post-endoplasmic reticulum compartments by a proprotein convertase-dependent mechanism. TAP mutant variants 1-2DELTAN and 2-1DELTAN show different effects on the quality control of Ag presentation | Rattus norvegicus |
| metabolism | critical role for the tapasin-docking site of TAP2 in the functional integrity of the MHC class I-peptide-loading complex. The translocation pathway of TAP opens out into a large endoplasmic reticulum lumenal cavity, confined by the membrane entry points of tapasin and MHC-I. Two lateral windows channel the antigenic peptides to MHC-I. Structures of PLC captured at distinct assembly states provide mechanistic insight into the recruitment and release of MHC-I. Molecular symbiosis of an ABC transporter and an endoplasmic reticulum chaperone network in MHC-I assembly, insight into the onset of the adaptive immune response. Assembled and nonassembled TAP1 uses different TMD subregions for tapasin binding | Rattus norvegicus |
| additional information | neither the N domain of TAP1 nor the N domain of TAP2 is required for ER-export and surface expression of MHC I | Rattus norvegicus |
| physiological function | the transporter associated with Ag processing (TAP) translocates antigenic peptides into the endoplasmic reticulum for binding onto MHC class I (MHC I) molecules. Tapasin organizes a peptide-loading complex (PLC) by recruiting MHC I and accessory chaperones to the N-terminal regions (N domains) of the TAP subunits TAP1 and TAP2. Tapasin, a type I transmembrane glycoprotein, is believed to play a key role in the formation of the PLC because it binds to MHC I molecules as well as to the transmembrane domains (TMDs) of the TAP subunits, TAP1 and TAP2. In the absence of tapasin, the stability of MHC I-peptide complexes is drastically reduced and the repertoire of surface-presented peptide Ags is altered, suggesting that tapasin acts as an editor that selects peptides for stable binding onto MHC I. TAP1 and TAP2 differ in the structural requirements for stable recruitment of accessory chaperones and the tapasin-docking site of TAP2 plays a pivotal role in the functional integrity of the PLC | Rattus norvegicus |
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