Limits...
A peptide-binding motif for I-A(g7), the class II major histocompatibility complex (MHC) molecule of NOD and Biozzi AB/H mice.

Harrison LC, Honeyman MC, Trembleau S, Gregori S, Gallazzi F, Augstein P, Brusic V, Hammer J, Adorini L - J. Exp. Med. (1997)

Bottom Line: Specific residues were not tolerated at these and some other positions.A motif for binding to I-A(g7) deduced from analysis of the model HEL epitope was present in 27/30 (90%) of peptides reported to be I-A(g7)-restricted T cell epitopes or eluted from I-A(g7).Scanning a set of overlapping peptides encompassing human proinsulin revealed the motif in 6/6 good binders (sensitivity = 100%) and 4/13 weak or non-binders (specificity = 70%).

View Article: PubMed Central - PubMed

Affiliation: Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Parkville, Australia.

ABSTRACT
The class II major histocompatibility complex molecule I-A(g7) is strongly linked to the development of spontaneous insulin-dependent diabetes mellitus (IDDM) in non obese diabetic mice and to the induction of experimental allergic encephalomyelitis in Biozzi AB/H mice. Structurally, it resembles the HLA-DQ molecules associated with human IDDM, in having a non-Asp residue at position 57 in its beta chain. To identify the requirements for peptide binding to I-A(g7) and thereby potentially pathogenic T cell epitopes, we analyzed a known I-A(g7)-restricted T cell epitope, hen egg white lysozyme (HEL) amino acids 9-27. NH2- and COOH-terminal truncations demonstrated that the minimal epitope for activation of the T cell hybridoma 2D12.1 was M12-R21 and the minimum sequence for direct binding to purified I-A(g7) M12-Y20/K13-R21. Alanine (A) scanning revealed two primary anchors for binding at relative positions (p) 6 (L) and 9 (Y) in the HEL epitope. The critical role of both anchors was demonstrated by incorporating L and Y in poly(A) backbones at the same relative positions as in the HEL epitope. Well-tolerated, weakly tolerated, and nontolerated residues were identified by analyzing the binding of peptides containing multiple substitutions at individual positions. Optimally, p6 was a large, hydrophobic residue (L, I, V, M), whereas p9 was aromatic and hydrophobic (Y or F) or positively charged (K, R). Specific residues were not tolerated at these and some other positions. A motif for binding to I-A(g7) deduced from analysis of the model HEL epitope was present in 27/30 (90%) of peptides reported to be I-A(g7)-restricted T cell epitopes or eluted from I-A(g7). Scanning a set of overlapping peptides encompassing human proinsulin revealed the motif in 6/6 good binders (sensitivity = 100%) and 4/13 weak or non-binders (specificity = 70%). This motif should facilitate identification of autoantigenic epitopes relevant to the pathogenesis and immunotherapy of IDDM.

Show MeSH

Related in: MedlinePlus

Minimal T cell epitope, HEL 12(M)–21(R), showing TCR  contact residues and L and Y primary anchors for binding to I-A97 at relative positions 6 and 9, and positions 3 and 8 at which specific residues are  also not tolerated for binding.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2196246&req=5

Figure 2: Minimal T cell epitope, HEL 12(M)–21(R), showing TCR contact residues and L and Y primary anchors for binding to I-A97 at relative positions 6 and 9, and positions 3 and 8 at which specific residues are also not tolerated for binding.

Mentions: Substitution of alanine (A) at each position in HEL 12–22 (Table 2) had no significant effect on binding, with the sole exceptions of positions L17 and Y20. Substitution at either of these two positions virtually abolished binding. On the other hand, while having no effect on binding, substitutions by A at K13, R14, H15, G16, and D18, and to a lesser extent at R21, abolished T cell activation. Removal of R21 (see Table 1) abolished T cell activation. Further substitutions of representative amino acids (D, K, P, Y, L, Q) at each position (Table 2) revealed varying levels of tolerance of specific residues/positions for binding (see below) and generally confirmed the results of the alanine substitutions on T cell activation. On the basis of these results, we can deduce that most residues in the minimal T cell epitope HEL 12–21 have TCR contacts and that two, L17 and Y20, are essential for binding to I-Ag7 (Fig. 2).


A peptide-binding motif for I-A(g7), the class II major histocompatibility complex (MHC) molecule of NOD and Biozzi AB/H mice.

Harrison LC, Honeyman MC, Trembleau S, Gregori S, Gallazzi F, Augstein P, Brusic V, Hammer J, Adorini L - J. Exp. Med. (1997)

Minimal T cell epitope, HEL 12(M)–21(R), showing TCR  contact residues and L and Y primary anchors for binding to I-A97 at relative positions 6 and 9, and positions 3 and 8 at which specific residues are  also not tolerated for binding.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196246&req=5

Figure 2: Minimal T cell epitope, HEL 12(M)–21(R), showing TCR contact residues and L and Y primary anchors for binding to I-A97 at relative positions 6 and 9, and positions 3 and 8 at which specific residues are also not tolerated for binding.
Mentions: Substitution of alanine (A) at each position in HEL 12–22 (Table 2) had no significant effect on binding, with the sole exceptions of positions L17 and Y20. Substitution at either of these two positions virtually abolished binding. On the other hand, while having no effect on binding, substitutions by A at K13, R14, H15, G16, and D18, and to a lesser extent at R21, abolished T cell activation. Removal of R21 (see Table 1) abolished T cell activation. Further substitutions of representative amino acids (D, K, P, Y, L, Q) at each position (Table 2) revealed varying levels of tolerance of specific residues/positions for binding (see below) and generally confirmed the results of the alanine substitutions on T cell activation. On the basis of these results, we can deduce that most residues in the minimal T cell epitope HEL 12–21 have TCR contacts and that two, L17 and Y20, are essential for binding to I-Ag7 (Fig. 2).

Bottom Line: Specific residues were not tolerated at these and some other positions.A motif for binding to I-A(g7) deduced from analysis of the model HEL epitope was present in 27/30 (90%) of peptides reported to be I-A(g7)-restricted T cell epitopes or eluted from I-A(g7).Scanning a set of overlapping peptides encompassing human proinsulin revealed the motif in 6/6 good binders (sensitivity = 100%) and 4/13 weak or non-binders (specificity = 70%).

View Article: PubMed Central - PubMed

Affiliation: Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Parkville, Australia.

ABSTRACT
The class II major histocompatibility complex molecule I-A(g7) is strongly linked to the development of spontaneous insulin-dependent diabetes mellitus (IDDM) in non obese diabetic mice and to the induction of experimental allergic encephalomyelitis in Biozzi AB/H mice. Structurally, it resembles the HLA-DQ molecules associated with human IDDM, in having a non-Asp residue at position 57 in its beta chain. To identify the requirements for peptide binding to I-A(g7) and thereby potentially pathogenic T cell epitopes, we analyzed a known I-A(g7)-restricted T cell epitope, hen egg white lysozyme (HEL) amino acids 9-27. NH2- and COOH-terminal truncations demonstrated that the minimal epitope for activation of the T cell hybridoma 2D12.1 was M12-R21 and the minimum sequence for direct binding to purified I-A(g7) M12-Y20/K13-R21. Alanine (A) scanning revealed two primary anchors for binding at relative positions (p) 6 (L) and 9 (Y) in the HEL epitope. The critical role of both anchors was demonstrated by incorporating L and Y in poly(A) backbones at the same relative positions as in the HEL epitope. Well-tolerated, weakly tolerated, and nontolerated residues were identified by analyzing the binding of peptides containing multiple substitutions at individual positions. Optimally, p6 was a large, hydrophobic residue (L, I, V, M), whereas p9 was aromatic and hydrophobic (Y or F) or positively charged (K, R). Specific residues were not tolerated at these and some other positions. A motif for binding to I-A(g7) deduced from analysis of the model HEL epitope was present in 27/30 (90%) of peptides reported to be I-A(g7)-restricted T cell epitopes or eluted from I-A(g7). Scanning a set of overlapping peptides encompassing human proinsulin revealed the motif in 6/6 good binders (sensitivity = 100%) and 4/13 weak or non-binders (specificity = 70%). This motif should facilitate identification of autoantigenic epitopes relevant to the pathogenesis and immunotherapy of IDDM.

Show MeSH
Related in: MedlinePlus