Nucleotide sequence of the constant region of a chicken μ heavy chain immonoglobulin mRNA

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Abstract
We have recently reported the sequence of a chicken Ig λ light chain cDNA clone, isolated from a spleen partial cDNA library (1).In this paper, we describe the characterization of a cDNA clone coding for the chicken constant (C) region of the secreted μ chain. This is the first report on the nucleotide and amino acid sequence of a chicken Ig heavy chain constant region. It contains the 3' untranslated region of the μ mRNA up to the poly(A) tail, and, in comparison with the mouse Cy sequence, displays the overall domain size and organization of a secreted μ chain, i.e. : a characteristic COOH-terminal region, a Cnμ4, a Cμ3, a Cμ2, and part of a Cyl domain. The sequence homology between these two species ranges from 45 % for the Cμ4 to 18% for the Cy2. Thus, the Cy sequence appears much less conserved between chicken and mouse than their respective light chain constant regions (1). These results, together with some distinctive features of the Cμ2 domain, may be of evolutionary relevance and will be further discussed.