Ahr^b-1

This allele encodes a high affinity, relatively heat stabile, 95 kDa receptor. PCR sequencing of cDNA revealed ten nucleotide differences between the coding sequences of the DBA/2J and C57BL/6J receptors. Five of the ten differences would cause amino acid changes. One of these, a C to T transition in exon 11 would change the arginine codon in the DBA/2J allele to an opal termination codon in the C57BL/6J allele. This change would prevent the 43 amino acid extension of mRNA translation predicted for the DBA/2J allele and account for the smaller size of the peptide produced by this allele (95 kDa vs 104 kDa for the DBA/2J allele). A second C to T transition changes a proline codon in the DBA/2J allele to leucine codon in the C57BL/6J allele, and would likely change secondary structure of the peptide and thus ligand affinity. (J:477, J:15153, J:17460)