title: Characterization of immunoglobulin gamma 1 from a monotreme, Tachyglossus aculeatus.
abstract: A full-length immunoglobulin gamma clone from the echidna (Tachyglossus aculeatus) was isolated from a spleen cDNA library. The clone was 1,664 base pairs long and encoded the entire open reading frame, incorporating the V, D, J and C regions. The echidna clone had approximately 41% identity and 67% similarity at the amino acid level with both marsupial and eutherian IgG molecules. The presence of IgG in the monotremes confirms that the appearance of IgG occurred prior to the separation of the three extant mammalian lineages, but after their separation from the reptilian lineage, pinpointing the date to between 310 and 170 million years ago. Phylogenetic analyses using the immunoglobulin sequence data strongly support the 'Theria' hypothesis, with the monotreme lineage diverging prior to the separation of the marsupial and eutherian lineages.
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
authors.forename: Katherine
authors.initials: K
authors.lastname: Belov
authors.forename: Lars
authors.initials: L
authors.lastname: Hellman
authors.forename: Desmond W
authors.initials: DW
authors.lastname: Cooper
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D007074:Immunoglobulin G / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D004442:Tachyglossidae / Q000235:genetics* / Q000276:immunology*
chemical_list: D018076:DNA, Complementary; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains