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Uniquely conformed peptide-containing beta 2-microglobulin-free heavy chains of HLA-B2705 on the cell surface
Pratap Malik1, Polina Klimovitsky, Lih-Wen Deng
1Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA.
The human class I MHC molecules are known to generally exist on the cell surface either as peptide-containing complexes of H chain (alpha-chain) and beta(2)-microglobulin (beta(2)m) or as beta(2)m-free H chains incapable of binding peptides. In this study, a uniquely conformed peptide-containing beta(2)m-free HLA-B2705 H chain has been isolated using the recently described highly efficient perfusion-affinity chromatography system for purification of class I MHC protein molecules. This form recognized by the mAb MARB4 is very closely associated with the remainder of the peptide containing HLA-B2705/beta(2)m complex reactive with mAb ME1 and is present to approximately 1-10% of mAb ME1 reactive forms on the cell surface. Also, HLA-B2705 purified using the mAb ME1 affinity column includes this unique mAb MARB4-reactive, unusually stable peptide-containing beta(2)m-free form. A peptide nonamer GRWRGWYTY was isolated and identified from this beta(2)m-free HLA-B2705 H chain and was used to assemble the mAb MARB4 reactive form efficiently on the surface of cells expressing HLA-B2705. The discovery of this form opens new avenues for further investigation of the role of HLA-B27 in spondyloarthropathies.
The human class I MHC molecules are known to generally exist on the cell surface either as peptide-containing complexes of H chain (alpha-chain) and beta(2)-microglobulin (beta(2)m) or as beta(2)m-free H chains incapable of binding peptides. In this study, a uniquely conformed peptide-containing beta(2)m-free HLA-B2705 H chain has been isolated using the recently described highly efficient perfusion-affinity chromatography system for purification of class I MHC protein molecules. This form recognized by the mAb MARB4 is very closely associated with the remainder of the peptide containing HLA-B2705/beta(2)m complex reactive with mAb ME1 and is present to approximately 1-10% of mAb ME1 reactive forms on the cell surface. Also, HLA-B2705 purified using the mAb ME1 affinity column includes this unique mAb MARB4-reactive, unusually stable peptide-containing beta(2)m-free form. A peptide nonamer GRWRGWYTY was isolated and identified from this beta(2)m-free HLA-B2705 H chain and was used to assemble the mAb MARB4 reactive form efficiently on the surface of cells expressing HLA-B2705. The discovery of this form opens new avenues for further investigation of the role of HLA-B27 in spondyloarthropathies.