English: Original caption from source paper:

Figure 3.

Structure of TCR-pMHC II complexes. TCR α- and β-chains (top) with CDR3 regions (CDR1, pink; CDR2, orange; CDR3, red) are positioned diagonally over MHC II α- and β-chains (bottom) and the presented peptide antigens (yellow). (A) Ni-specific TCR ANi-2.3 (TRAV8-TRBV19) in complex with a peptide mimotope (pdb ID code 4h1l). Lys7 likely replaces Ni in this structure with Asp95 being an essential contact point (green stick representation, [209]). (B) TCR 3 A6 (MBP 89-101-specific, TRAV9-2-TRBV5) represents the only available TCR-pMHC II structure of a human TRAV9-2 TCR (pdb ID code 1 zgl). His81 is a major TCR contact point in the MHC II β-chain and is in close proximity with Tyr36 in the TCR α-chain CDR1 of TRAV9-2 (pink stick representation). A recent study found that approximately 35% of Ni-specific TCR expressed TRAV9-2 compared to ~5% in the random repertoire [115]. The depicted TCR do not express a histidine in their CDR3 regions, which constitutes an independent recently discovered major Ni binding mechanism [115] (see Section 3.2). Created with Pymol.