CTX, a novel molecule specifically expressed on the surface of cortical thymocytes in Xenopus.
CTX, a novel developmentally regulated type-I transmembrane protein is expressed specifically by a large fraction of cortical thymocytes in the amphibian Xenopus. This apparently monomeric 55-kDa glycoprotein is composed of two immunoglobulin domains, one variable (V) and one constant (C2 type), followed by a transmembrane and a 64-amino acid cytoplasmic domain. The first immunoglobulin domain is a V-J segment that is generated without gene rearrangement. In the genome, the V and C2 domains are both encoded by two half-domain exons. Two CTX loci are found per haploid genome, and they exhibit sequence differences with a high replacing/silent ratio in the CDR1-like region of the V domain, suggesting that these differences were selected. The cytoplasmic domain contains a motif that is highly conserved evolutionarily in several types of proteins, including adenylyl cyclases. Based on its unique tissue distribution, the variability of its V region and the motif of its cytoplasmic domain, CTX is a candidate for a new type of specific molecule involved in thymocyte selection.
Chrétien
I
I
Basel Institute for Immunology, Switzerland.
Robert
J
J
Marcuz
A
A
Garcia-Sanz
J A
JA
Courtet
M
M
Du Pasquier
L
L
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface / Q000096:biosynthesis*; D001483:Base Sequence; D015415:Biomarkers; D017637:Clonal Deletion; D016384:Consensus Sequence; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D015329:Gene Rearrangement, T-Lymphocyte; D005796:Genes; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D011487:Protein Conformation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D013950:Thymus Gland / Q000378:metabolism*; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D015415:Biomarkers; D018076:DNA, Complementary; D008565:Membrane Proteins; D029867:Xenopus Proteins; C099384:ctx-A protein, Xenopus