Analysis of polymorphisms in the major expressed class I locus (B-FIV) of the chicken |
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Authors: | H D Hunt Janet E Fulton |
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Institution: | (1) United States Department of Agriculture, Agriculture Research Service, Avian Disease and Oncology Laboratory, 3606 East Mount Hope Road, East Lansing, MI 48823, USA, US;(2) Hy-Line International, 1915 Sugar Grove, PO Box 310, Dallas Center, IA 50063, USA, US |
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Abstract: | We analyzed the polymorphic nature of eleven alleles expressed by the major class I locus (B-FIV) in chickens. Similar to mammalian class I loci, the nucleotide substitutions with high variability occur in exons 2 and
3 encoding the α1 and α2 domains. However, the nonsynonymous to synonymous ratio of nucleotide substitutions in exon 3 encoding
the α helix and β sheets is reversed compared with HLA. The region of exon 3 encoding the α2 helix demonstrates a much lower
nonsynonymous to synonymous ratio, suggesting evolutionary selection of a more conserved α2 helix in B-FIV compared with HLA.
Amino acid residues with high Wu-Kabat variability are typically located in positions predicted to impact antigen presentation.
B-FIV amino acid residues predicted to interact with the CDR1α region of the T-cell receptor (Tcr) demonstrate less variability
than in mouse and human class I alleles. The combination of a reduced nonsynonymous to synonymous ratio in exon 3 encoding
the α2 helix and the limited variability in CDR1α contact residues is discussed with regard to concerted evolution between
a minimal major histocompatibility complex and compaction of Tcr variable gene segments in the chicken.
Received: 18 Juli 1997 / Revised: 21 November 1997 |
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Keywords: | Mhc Class I BF Concerted evolution |
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