A conformational change in the human major histocompatibility complex protein HLA-DR1 induced by peptide binding |
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Authors: | Zarutskie J A Sato A K Rushe M M Chan I C Lomakin A Benedek G B Stern L J |
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Affiliation: | Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139, USA. |
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Abstract: | To investigate a conformational change accompanying peptide binding to class II MHC proteins, we probed the structure of a soluble version of the human class II MHC protein HLA-DR1 in empty and peptide-loaded forms. Peptide binding induced a large decrease in the effective radius of the protein as determined by gel filtration, dynamic light scattering, and analytical ultracentrifugation. It caused a substantial increase in the cooperativity of thermal denaturation and induced alterations in MHC polypeptide backbone structure as determined by circular dichroism. These changes suggest a condensation of the protein around the bound peptide. An antibody specific for beta58-69 preferentially bound the empty protein, indicating that the peptide-induced conformational change involves the beta-subunit helical region. The conformational change may have important implications for the mechanisms of intracellular antigen presentation pathways. |
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