Invariant chain made in Escherichia coli has an exposed N-terminal segment that blocks antigen binding to HLA-DR1 and a trimeric C-terminal segment that binds empty HLA-DR1.
AUTOR(ES)
Park, S J
RESUMO
Invariant chain (Ii), a membrane glycoprotein, binds class II major histocompatibility complex (MHC) glycoproteins, probably via its class II-associated Ii peptide (CLIP) segment, and escorts them toward antigen-containing endosomal compartments. We find that a soluble, trimeric ectodomain of Ii expressed and purified from Escherichia coli blocks peptide binding to soluble HLA-DR1. Proteolysis indicates that Ii contains two structural domains. The C-terminal two-thirds forms an alpha-helical domain that trimerizes and interacts with empty HLA-DR1 molecules, augmenting rather than blocking peptide binding. The N-terminal one-third, which inhibits peptide binding, is proteolytically susceptible over its entire length. In the trimer, the N-terminal domains act independently with each CLIP segment exposed and free to bind an MHC class II molecule, while the C-terminal domains act as a trimeric unit.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=40617Documentos Relacionados
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