title: Biochemical analysis of the Xenopus laevis TCR/CD3 complex supports the "stepwise evolution" model.
abstract: The TCR/CD3 complex of a cold-blooded vertebrate, the amphibian Xenopus laevis, was biochemically characterized with a cross-reactive polyclonal antiserum recognizing a conserved epitope in the cytoplasmic domain of CD3E. The specificity and utility of this reagent was validated by Western blot analysis and immunoprecipitation of the well-characterized chicken TCR/CD3 complex. Cross-reactivity with the X. laevis CD3E protein was demonstrated by specific staining of sorted CD8+ cells. Immunohistology on both tadpoles and adult tissues suggests this antiserum will be instrumental in the localization of Xenopus T cells and most likely NK cells. Double staining of tissue sections with an anti-CD8 monoclonal antibody confirmed that this staining is specific. The antiserum was also used for the biochemical analyses of X. laevis TCR/CD3 complex. The 75-kDa alphabeta TCR heterodimer could be separated into a 40-kDa acidic TCR alpha chain and a 35-kDa basic TCR beta chain. Two CD3 proteins, both comigrating at approximately 19 kDa, were associated with the TCR heterodimer. Removal of N-linked carbohydrates yielded CD3 proteins of 19 kDa and 16.5 kDa, most likely representing the CD3epsilon and CD3gamma/delta homologues, respectively. An additional band of 110 kDa represents a multimeric complex of the TCR heterodimer covalently linked to a CD3 dimer. These properties of the Xenopus TCR/CD3 complex substantiate a stepwise evolutionary model for the CD3 protein family.
authors.affiliation: Institute for Animal Physiology, Munich, Germany. thomas.goebel@tiph.vetmed.uni-muenchen.de
authors.forename: T W
authors.initials: TW
authors.lastname: Göbel
authors.forename: E L
authors.initials: EL
authors.lastname: Meier
authors.forename: L
authors.initials: L
authors.lastname: Du Pasquier
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017252:CD3 Complex / Q000737:chemistry / Q000276:immunology; D016384:Consensus Sequence; D003429:Cross Reactions; D019281:Dimerization; D000939:Epitopes / Q000276:immunology; D019143:Evolution, Molecular; D006031:Glycosylation; D007106:Immune Sera; D007814:Larva; D046911:Macromolecular Substances; D008954:Models, Biological; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000166:cytology; D013945:Thymoma / Q000473:pathology; D013953:Thymus Neoplasms / Q000473:pathology; D014982:Xenopus laevis / Q000235:genetics / Q000254:growth & development / Q000276:immunology*
chemical_list: D017252:CD3 Complex; D000939:Epitopes; D007106:Immune Sera; D046911:Macromolecular Substances; D017260:Receptor-CD3 Complex, Antigen, T-Cell