Abstract.
The J-chain protein is a M r 15,000 polypeptide associated with polymeric IgA and IgM. The complete cDNA sequences of human, mouse, cow, brushtail possum, chicken and frog J chains have been previously reported, but nothing is known about the cDNA and amino acid sequences of reptilian J chain. Here, we determined a turtle J-chain cDNA sequence by RT-PCR and RACE, and examined J-chain mRNA and protein expression by Northern blotting and immunohistochemistry. This turtle J-chain cDNA was 1,934 bp and had an open reading frame of 477 nucleotides, encoding 159 amino acids. The mature J-chain protein is composed of 137 amino acids, M r ~15,000. The deduced amino acid sequence of the turtle J chain was highly homologous to that of human (60%), mouse (61%), cow (60%), rabbit (60%), chicken (69%), brushtail possum (65%), Rana catesbeiana (47%) and Xenopus laevis (58%). Eight cysteine residues were located at the same positions as in these other species, with the exception of X. laevis. PROSITE database analysis indicated the presence of two N-glycosylation sites in turtle, one of which was novel. Northern blot analysis revealed that turtle J-chain mRNA was expressed in lung, stomach, spleen and intestine. In addition, immunohistochemistry showed J-chain-positive plasma cells in the intestine and spleen. These results suggest the presence of a mucosal immune system mainly composed of J-chain-containing Ig in the turtle.
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Iwata, A., Iwase, T., Ogura, Y. et al. Cloning and expression of the turtle (Trachemys scripta) immunoglobulin joining (J)-chain cDNA. Immunogenetics 54, 513–519 (2002). https://doi.org/10.1007/s00251-002-0492-2
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DOI: https://doi.org/10.1007/s00251-002-0492-2