title: Evolution of vertebrate IgM: complete amino acid sequence of the constant region of Ambystoma mexicanum mu chain deduced from cDNA sequence.
abstract: cDNA clones coding for the constant region of the Mexican axolotl (Ambystoma mexicanum) mu heavy immunoglobulin chain were selected from total spleen RNA, using a cDNA polymerase chain reaction technique. The specific 5'-end primer was an oligonucleotide homologous to the JH segment of Xenopus laevis mu chain. One of the clones, JHA/3, corresponded to the complete constant region of the axolotl mu chain, consisting of a 1362-nucleotide sequence coding for a polypeptide of 454 amino acids followed in 3' direction by a 179-nucleotide untranslated region and a polyA+ tail. The axolotl C mu is divided into four typical domains (C mu 1-C mu 4) and can be aligned with the Xenopus C mu with an overall identity of 56% at the nucleotide level. Percent identities were particularly high between C mu 1 (59%) and C mu 4 (71%). The C-terminal 20-amino acid segment which constitutes the secretory part of the mu chain is strongly homologous to the equivalent sequences of chondrichthyans and of other tetrapods, including a conserved N-linked oligosaccharide, the penultimate cysteine and the C-terminal lysine. The four C mu domains of 13 vertebrate species ranging from chondrichthyans to mammals were aligned and compared at the amino acid level. The significant number of mu-specific residues which are conserved into each of the four C mu domains argues for a continuous line of evolution of the vertebrate mu chain. This notion was confirmed by the ability to reconstitute a consistent vertebrate evolution tree based on the phylogenic parsimony analysis of the C mu 4 sequences.
authors.affiliation: Université Pierre et Marie Curie, Paris, France.
authors.forename: J S
authors.initials: JS
authors.lastname: Fellah
authors.forename: M V
authors.initials: MV
authors.lastname: Wiles
authors.forename: J
authors.initials: J
authors.lastname: Charlemagne
authors.forename: J
authors.initials: J
authors.lastname: Schwager
mesh_terms: D000557:Ambystoma / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D017124:Conserved Sequence; D004247:DNA / Q000737:chemistry*; D000939:Epitopes; D007127:Immunoglobulin Constant Regions / Q000737:chemistry*; D007075:Immunoglobulin M / Q000737:chemistry* / Q000235:genetics; D007148:Immunoglobulin mu-Chains / Q000737:chemistry*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D014981:Xenopus / Q000276:immunology
chemical_list: D000939:Epitopes; D007127:Immunoglobulin Constant Regions; D007075:Immunoglobulin M; D007148:Immunoglobulin mu-Chains; D012333:RNA, Messenger; D004247:DNA