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

Seong Joon Park, Scheherazade Sadeoh-Nasseri, Don C. Wiley

Research output: Contribution to journalArticle

Abstract

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 colt blocks peptide binding to soluble HLA-DR1. Proteolysis indicates that Ii contains two structural domains. The C-terminal two-thirds forms an α-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.

Original languageEnglish (US)
Pages (from-to)11289-11293
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume92
Issue number24
DOIs
StatePublished - Nov 21 1995

Keywords

  • antigen processing
  • major histocompatibility complex class II

ASJC Scopus subject areas

  • General

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