Molecular analysis of TCR and peptide/MHC interaction using P18-I10-derived peptides with a single D-amino acid substitution

¹ Department of Microbiology and Immunology, Nippon Medical School
² Department of Physics, Nippon Medical School

^* To whom correspondence should be addressed. E-mail: htkuhkai{at}nms.ac.jp.

Submitted on August 16, 2006
Revised on October 5, 2006
Accepted on 13 December 2006

	Abstract

For the structural analysis of T cell receptor (TCR) and peptide/MHC interaction, a series of peptides with a single amino acid substitution by a corresponding D-amino acid, having the same weight, size, and charge, within P18-I10 (aa318-327: RGPGRAFVTI), an immunodominant epitope of HIV-1 IIIB envelope glycoprotein, restricted by the H-2D^d class I MHC molecule has been synthesized. Using those peptides, we have observed that the replacement at positions 324F, 325V, 326T, and 327I with each corresponding D-amino acid induced marked reduction of the potency to sensitize targets for P18-I10-specific murine CD8⁺ cytotoxic T lymphocytes (CTLs), LINE-IIIB, recognition. For further analyzing the role of amino acid at position 325, the most critical site for determining epitope specificity, we have developed a CTL line [LINE-IIIB(325D)] and its offspring clones specific for the epitope I-10(325v) having a D-valine (v) at position 325. Taking advantage of two distinct sets of CD8⁺ CTLs restricted by the same D^d, three-dimensional (3D) structural analysis on TCR and peptide/MHC complexes by molecular modeling was performed, which indicates that the critical amino acids within the TCRs for interacting with 325V or 325v appear to belong to the complementarity-determining region (CDR) 1 but not to the CDR3 region of V chain.

Key Words: D-amino acid, MHC, T cell receptor (TCR), cytotoxic T lymphocyte (CTL), epitope, molecular modeling