The human class II MHC protein HLA-DR1 assembles as empty alpha beta heterodimers in the absence of antigenic peptide.
We have produced the human class II histocompatibility protein, HLA-DR1, as a soluble, secreted glycoprotein in insect cells infected with baculoviruses carrying truncated alpha and beta subunit genes. The peptide-binding site is empty, and the empty molecules are fully competent to bind antigenic peptide. We used the empty molecules to measure an intrinsic rate for peptide association, and to investigate the role of peptide in stabilizing the class II structure. Peptide binding kinetics for the empty molecule are only 10-fold faster than for peptide exchange into an occupied site, suggesting that a conformational change may accompany peptide binding. The native alpha beta heterodimer assembles in the absence of antigenic peptide, but peptide binding stabilizes the empty heterodimer against aggregation and against SDS-induced denaturation.
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
L J
LJ
Stern
D C
DC
Wiley
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line / Q000378:metabolism; D000939:Epitopes / Q000378:metabolism*; D015798:HLA-DR1 Antigen / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D006801:Humans; D007313:Insecta / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D014162:Transfection
D000911:Antibodies, Monoclonal; D000939:Epitopes; D015798:HLA-DR1 Antigen