Js. Fellah et al., PHYLOGENY OF IMMUNOGLOBULIN HEAVY-CHAIN ISOTYPES - STRUCTURE OF THE CONSTANT-REGION OF AMBYSTOMA-MEXICANUM UPSILON-CHAIN DEDUCED FROM CDNA SEQUENCE, Immunogenetics, 38(5), 1993, pp. 311-317
An RNA polymerase chain reaction strategy was used to amplify and clon
e a cDNA segment encoding for the complete constant part of the axolot
l IgY heavy (Cupsilon) chain. Cupsilon is 433 amino acids long and org
anized into four domains (Cupsilon1-Cupsilon4); each has the typical i
nternal disulfide bond and invariant tryptophane residues. Axolotl Cup
silon is most closely related to Xenopus Cupsilon (40% identical amino
acid residues) and Cupsilon1 shares 46.4% amino acid residues among t
hese species. The presence of additional cysteines in Cupsilon1 and Cu
psilon2 domains is consistent with an additional intradomain S-S bond
similar to that suggested for Xenopus Cupsilon and Cchi, and for the a
vian Cupsilon and the human Cepsilon. Cupsilon4 ends with the Gly-Lys
dipeptide characteristic of secreted mammalian Cgamma3, human Cepsilon
4, and avian and anuran Cupsilon4, and contains the consensus [G/GT(AA
)] nucleotide splice signal sequence for joining Cupsilon4 to the tran
smembrane region. These results are consistent with the hypothesis of
an ancestral structural relationship between amphibian, avian upsilon
chains, and mammalian epsilon chains. However, these molecules have di
fferent biological properties: axolotl IgY is secretory Ig, anuran and
avian IgY behave like mammalian IgG, and mammalian IgE is implicated
in anaphylactic reactions.