We have determined the structure of a second human histocompatibility glycoprotein, HLA-Aw68, by X-ray crystallography and refined it to a resolution of 2.6 A. Overall, the structure is extremely similar to that of HLA-A2 (refs 1, 2; and M.A.S. et al., manuscript in preparation), although the 11 amino-acid substitutions at polymorphic residues in the antigen-binding cleft alter the detailed shape and electrostatic charge of that site ...
We have determined the structure of a second human histocompatibility glycoprotein, HLA-Aw68, by X-ray crystallography and refined it to a resolution of 2.6 A. Overall, the structure is extremely similar to that of HLA-A2 (refs 1, 2; and M.A.S. et al., manuscript in preparation), although the 11 amino-acid substitutions at polymorphic residues in the antigen-binding cleft alter the detailed shape and electrostatic charge of that site. A prominent negatively charged pocket within the cleft extends underneath the alpha-helix of the alpha 1-domain, providing a potential subsite for recognizing a positively charged side chain or peptide N terminus. Uninterpreted electron density, presumably representing an unknown 'antigen(s)', which seems to be different from that seen in the HLA-A2 structure, occupies the cleft and extends into the negatively charged pocket in HLA-Aw68. The structures of HLA-Aw68 and HLA-A2 demonstrate how polymorphism creates and alters subsites (pockets) positioned to bind peptide side chains, thereby suggesting the structural basis for allelic specificity in foreign antigen binding.
Related Citations:
Structure of the Human Class I Histocompatibility Antigen, Hla-A2 Bjorkman, P.J., Saper, M.A., Samraoui, B., Bennett, W.S., Strominger, J.L., Wiley, D.C. (1987) Nature 329: 506
The Foreign Antigen Binding Site and T Cell Recognition Regions of Class I Histocompatibility Antigens Bjorkman, P.J., Saper, M.A., Samraoui, B., Bennett, W.S., Strominger, J.L., Wiley, D.C. (1987) Nature 329: 512
Crystallization and X-Ray Diffraction Studies on the Histocompatibility Antigens Hla-A2 and Hla-A28 from Human Cell Membranes Bjorkman, P.J., Strominger, J.L., Wiley, D.C. (1985) J Mol Biol 186: 205
Organizational Affiliation:
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
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