title: Thermal stability of MHC class I-beta 2-microglobulin peptide complexes in the endoplasmic reticulum is determined by the peptide occupancy of the transporter associated with antigen processing complex.
abstract: Once MHC class I heavy chain binds beta(2)-microglobulin (beta(2)m) within the endoplasmic reticulum, an assembly complex comprising the class I heterodimer, TAP, TAPasin, calreticulin, and possibly Erp57 is formed before the binding of high affinity peptide. TAP-dependent delivery of high affinity peptide to in vitro translated K(b)beta(2)m complexes within microsomes (TAP(+)/TAPasin(+)) was studied to determine at which point peptide binding becomes resistant to thermal denaturation. It was determined that the thermal stability of K(b)-beta(2)m-peptide complexes depends on the timing of peptide binding to K(b)beta(2)m relative to TAP binding high affinity peptide. Premature exposure of the TAP complex to high affinity peptide before its association with class I heavy chain results in K(b)beta(2)m-peptide-TAP complexes that lose peptide upon exposure to elevated temperature after solubilization away from microsome-associated proteins. These findings suggest that the order in which class I heavy chain associates with endoplasmic reticulum-resident chaperones and peptide determines the stability of K(b)beta(2)m-peptide complexes.
authors.affiliation: Departments of Biochemistry and Molecular Biology, Mayo Clinic/Foundation, Rochester, MN 55905, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Owen
authors.forename: L R
authors.initials: LR
authors.lastname: Pease
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D017951:Antigen Presentation / Q000235:genetics; D017920:Antiporters / Q000276:immunology / Q000378:metabolism; D004527:Egg Proteins / Q000276:immunology / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000276:immunology / Q000378:metabolism*; D006183:H-2 Antigens / Q000378:metabolism*; D006358:Hot Temperature; D007136:Immunoglobulins / Q000276:immunology / Q000378:metabolism; D008285:Major Histocompatibility Complex; D026901:Membrane Transport Proteins; D051379:Mice; D008861:Microsomes / Q000276:immunology / Q000378:metabolism; D010047:Ovalbumin / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D014176:Protein Biosynthesis / Q000276:immunology; D017510:Protein Folding; D011499:Protein Processing, Post-Translational / Q000276:immunology; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000378:metabolism*
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D017920:Antiporters; D004527:Egg Proteins; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; C110366:OVA-8; D010446:Peptide Fragments; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; D001613:beta 2-Microglobulin; C107762:tapasin; D010047:Ovalbumin