Figure 1.
Structural characteristics of major histocompatibility complex (MHC) class I and MHC class II proteins and their compartment-dependent loading with processed peptides. (A) Domain topology of a pMHC class I and pMHC class II complex. (B) Structure of HLA-A68 in complex with an HIV-derived peptide (PDB: 4HWZ, left) and HLA-DR1 in complex with a hemagglutinin-derived peptide (1DLH, right). Indicated are the supposed interaction sites of MHC class I with tapasin and of MHC class II with DM as dashed gray lines. The peptide is shown in yellow with its N and C-terminus marked and relevant pockets are labeled green (C) Simplified illustration of MHC class I (left) and II (right) processing and peptide-editing pathways. CLIP, class II-associated invariant chain peptide; Caln., calnexin; Calr., calreticulin; ER, endoplasmic reticulum; PLC, peptide loading complex.