Conformational restriction of the Tyr53 side-chain in the decapeptide HE. |
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Authors: | J R Casimir K Iterbeke W Van Den Nest M C Trescol-Biémont H Dumortier S Muller D Gerlier C Rabourdin-Combe D Tourwé J Paris |
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Institution: | Laboratoire de Chimie Thérapeutique, Université Claude Bernard, Lyon, France. R.Casimir@ibmc.u-strasbg.fr |
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Abstract: | A series of conformationally restricted analogs of the hen egg lysozyme (HEL) decapeptide 52-61 in which the conformationally flexible Tyr53 residue was replaced by several more constrained tyrosine and phenylalanine analogs was prepared. Among these tyrosine and phenylalanine analogs were 1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid (Htc), 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic), 4-amino- 1,2,4,5-tetrahydro-8-hydroxy-2-benzazepine-3-one (Hba), 4-amino-1,2,4,5-tetrahydro-2-benzazepine-3-one (Aba), 2-amino-6-hydroxytetralin-2-carboxylic acid (Hat) and 2-amino-5-hydroxyindan-2-carboxylic acid (Hai) in which the rotations around Calpha-Cbeta and Cbeta-Cgamma were restricted because of cyclization of the side-chain to the backbone. Synthesis of Pht-Hba-Gly-OH using a modification of the Flynn and de Laszlo procedure is described. Analogs of beta-methyltyrosine (beta-MeTyr) in which the side-chains were biased to particular side-chain torsional angles because of substitution at the beta-hydrogens were also prepared. These analogs of HEL52-61] peptide were tested for their ability to bind to the major histocompatibility complex class II I-Ak molecule and to be recognized in this context by two T-cell hybridomas, specific for the parent peptide HEL52-61]. The data showed that the conformation and also the configuration of the Tyr53 residue influenced both the binding of the peptide to I-Ak and the recognition of the peptide/I-Ak complex by a T-cell receptor. |
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