1. Stoichiometry of HLA class II-invariant chain oligomers.
- Author
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Koch N, Zacharias M, König A, Temme S, Neumann J, and Springer S
- Subjects
- Amino Acid Sequence, Animals, Antigen-Presenting Cells chemistry, Antigen-Presenting Cells immunology, Antigens, Differentiation, B-Lymphocyte chemistry, COS Cells, Cell Fractionation, Cell Line, Tumor, Chlorocebus aethiops, HLA-D Antigens chemistry, HLA-DP Antigens analysis, HLA-DP Antigens chemistry, HLA-DP Antigens metabolism, HLA-DQ Antigens analysis, HLA-DQ Antigens chemistry, HLA-DQ Antigens metabolism, HLA-DR Antigens analysis, HLA-DR Antigens chemistry, HLA-DR Antigens metabolism, Histocompatibility Antigens Class II chemistry, Humans, Models, Molecular, Molecular Sequence Data, Osmolar Concentration, Protein Structure, Quaternary, Ultracentrifugation, Antigens, Differentiation, B-Lymphocyte analysis, Antigens, Differentiation, B-Lymphocyte metabolism, HLA-D Antigens analysis, Histocompatibility Antigens Class II analysis, Histocompatibility Antigens Class II metabolism, Protein Multimerization physiology
- Abstract
Background: The HLA gene complex encodes three class II isotypes, DR, DQ, and DP. HLA class II molecules are peptide receptors that present antigens for recognition by T lymphocytes. In antigen presenting cells, the assembly of matched α and β subunits to heterodimers is chaperoned by invariant chain (Ii). Ii forms a homotrimer with three binding sites for class II heterodimers. The current model of class II and Ii structure states that three αβ heterodimers bind to an Ii trimer., Methodology/principal Findings: [corrected] We have now analyzed the composition and size of the complexes of class II and Ii using epitope tagged class II subunits and density gradient experiments. We show here that class II-Ii oligomers consist of one class II heterodimer associated with one Ii trimer, such that the DR, DQ and DP isotypes are contained within separate complexes with Ii., Conclusion/significance: We propose a structural model of the class II-Ii oligomer and speculate that the pentameric class II-Ii complex is bent towards the cell membrane, inhibiting the binding of additional class II heterodimers to Ii.
- Published
- 2011
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