Chicken T-Cell Receptor β-Chain Diversity: An Evolutionarily Conserved Dβ-Encoded Glycine Turn Within the Hypervariable CDR3 Domain

Unlike mammals, chickens generate an immunoglobulin (Ig) repertoire by a developmentally regulated process of intrachromosomal gene conversion, which results in nucleotide substitutions throughout the variable regions of the Ig heavy- and light-chain genes. In contrast to chicken Ig genes, we show i...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1991-09, Vol.88 (17), p.7699-7703
Main Authors: McCormack, W T, Tjoelker, L W, Stella, G, Postema, C E, Thompson, C B
Format: Article
Language:lat ; eng
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Binding Sites
Biological Evolution
Chick Embryo
Chickens
Gene Rearrangement, beta-Chain T-Cell Antigen Receptor
Genetic Variation
Glycine
Major Histocompatibility Complex
Molecular Sequence Data
Oligonucleotide Probes
Protein Conformation
Receptors, Antigen, T-Cell - genetics
Sequence Homology, Nucleic Acid
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Summary:Unlike mammals, chickens generate an immunoglobulin (Ig) repertoire by a developmentally regulated process of intrachromosomal gene conversion, which results in nucleotide substitutions throughout the variable regions of the Ig heavy- and light-chain genes. In contrast to chicken Ig genes, we show in this report that diversity of the rearranged chicken T-cell receptor (TCR) β-chain gene is generated by junctional heterogeneity, as observed in rearranged mammalian TCR genes. This junctional diversity increases during chicken development as a result of an increasing base-pair addition at the Vβ-Dβand Dβ-Jβjoints (where V, D, and J are the variable, diversity, and joining gene segments). Despite the junctional hypervariability, however, almost all functional Vβ-Dβ-Jβjunctions appear to encode a glycine-containing β-turn. Such a turn may serve to position the amino acid side chains of a hypervariable TCR β-chain loop with respect to the antigen-binding groove of the major histocompatibility complex molecule. Consistent with this hypothesis, the germ-line Dβnucleotide sequences of chickens, mice, rabbits, and humans have been highly conserved and encode a glycine in all three reading frames.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.88.17.7699