Site recognition by protein-primed T cells shows a non-specific peptide size requirement beyond the essential residues of the site. Demonstration by defining an immunodominant T site in myoglobin.
In previous studies, six T sites within myoglobin (Mb) were localized. To define precisely the boundaries of the T sites, a new approach is introduced and applied here to the T site residing within residues 107-120 of Mb. Two sets of peptides were synthesized. One set represents a stepwise elongation by one-residue increments of the Mb sequence. The other set represents an identical stepwise addition of one-residue increments of the Mb sequence, but which were extended by additional unrelated (nonsense) residues to a uniform size of 14 residues. The longer peptides (nonsense-extended) usually gave higher proliferative responses than did their shorter counterparts having the same Mb region. Thus a minimum peptide size is required for optimal T-cell stimulation. The T site subtends, in three high-responder mouse strains, residues 109-119 or 110-120, depending on strain, and, in three low-responder strains, maps to residues 108-120. Thus, in this case, the T site coincides with the site of B-cell recognition and resides in a small discrete surface region of the protein chain.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002455:Cell Division; D004306:Dose-Response Relationship, Immunologic; D000939:Epitopes / Q000032:analysis*; D051379:Mice; D008815:Mice, Inbred Strains; D009211:Myoglobin / Q000276:immunology*; D010455:Peptides / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
D000596:Amino Acids; D000939:Epitopes; D009211:Myoglobin; D010455:Peptides