The outermost N-terminal region of tapasin facilitates folding of major histocompatibility complex class I

Tapasin (Tpn) is an ER chaperone that is uniquely dedicated to MHC-I biosynthesis. It binds MHC-I molecules, integrates them into peptide-loading complexes, and exerts quality control of the bound peptides; only when an "optimal peptide" is bound will the MHC-I be released and exported to the cell surface for presentation to T cells. The exact mechanisms of Tpn quality control and the criteria for being an optimal peptide are still unknown. Here, we have generated a recombinant fragment of human Tpn, Tpn(1-87) (representing the 87 N-terminal and ER-luminal amino acids of the mature Tpn protein). Using a biochemical peptide-MHC-I-binding assay, recombinant Tpn(1-87) was found to specifically facilitate peptide-dependent folding of HLA-A*0201. Furthermore, we used Tpn(1-87) to generate a monoclonal antibody, alpha Tpn(1-87/80), specific for natural human Tpn and capable of cellular staining of ER localized Tpn. Using overlapping peptides, the epitope of alpha Tpn(1-87)/80 was located to Tpn(40-44), which maps to a surface-exposed loop on the Tpn structure. Together, these results demonstrate that the N-terminal region of Tpn can be recombinantly expressed and adopt a structure, which at least partially resembles that of WT Tpn, and that this region of Tpn features chaperone activity facilitating peptide binding of MHC-I.

Geironson Ulfsson, LindaLund University,Lunds universitet,Neurokirurgi,Sektion IV,Institutionen för kliniska vetenskaper, Lund,Medicinska fakulteten,Neurosurgery,Section IV,Department of Clinical Sciences, Lund,Faculty of Medicine(Swepub:lu)immu-lge (author)
Darabi, AnnaLund University,Lunds universitet,Neurokirurgi,Sektion IV,Institutionen för kliniska vetenskaper, Lund,Medicinska fakulteten,Neurosurgery,Section IV,Department of Clinical Sciences, Lund,Faculty of Medicine(Swepub:lu)wbl-ajo (author)
Harndahl, Mikkel (author)
Schafer-Nielsen, Claus (author)
Skjodt, Karsten (author)
Buus, Soren (author)
Paulsson, Kajsa MLund University,Lunds universitet,Immunologi,Forskargrupper vid Lunds universitet,Immunology,Lund University Research Groups(Swepub:lu)med-k_p (author)
NeurokirurgiSektion IV (creator_code:org_t)

By the author/editor: Roder, Gustav; Geironson Ulfsso ...; Darabi, Anna; Harndahl, Mikkel; Schafer-Nielsen, ...; Skjodt, Karsten; show more...; Buus, Soren; Paulsson, Kajsa ...; show less...

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MEDICAL AND HEALTH SCIENCES: MEDICAL AND HEAL ...; and Basic Medicine; and Immunology in th ...

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