Borst J, Coligan J E, Oettgen H, Pessano S, Malin R, Terhorst C
Nature. 1984;312(5993):455-8. doi: 10.1038/312455a0.
The T3/T-cell receptor complex on the surface of human thymus-derived lymphocytes consists of four glycoproteins: the alpha-chain of relative molecular mass (Mr) 40,000-50,000 (40-50K), the beta-chain (37-45K); the gamma-chain (25K) and the delta-chain (20K). The T3 alpha- and beta-chains have been identified as clonotypic T-cell receptors, but functionally the T3/T-cell receptor chains seem to form a single complex: monoclonal antibodies directed at the 20K T3 components are mitogenic for normal human T lymphocytes and, at higher concentrations, anti-clonotypic and anti-20K reagents block T-cell function. Recently, Zanders et al. showed that incubation of human T-helper clones with high concentrations of antigen abolishes antigen-specific proliferation and induces disappearance of T3 from the cell surface. Thus, the T3/T-cell receptor complex consists of two variable subunits, the T3 alpha- and beta-chains, which interact with antigen and the monomorphic 20K/25K T3 chains. Recently, the existence of a fifth polypeptide chain, the unglycosylated T3 epsilon-chain, has been postulated. Here we confirm that a 20K epsilon-chain does exist. The T3 epsilon-chain differs from the T3 delta-chain in primary structure as judged by N-terminal amino acid sequencing, peptide mapping and immunoblotting with anti-T3-delta and anti-T3-epsilon antibodies. Treatment with endoglycosidase F revealed two nonglycosylated T3 delta polypeptide backbone chains (16K and 14K) with identical amino termini. Together with previous pulse-chase experiments this observation suggests that the 14K T3 polypeptide is derived from the 16K T3 precursor by proteolytic processing near the C-terminus of the molecule.
人胸腺来源淋巴细胞表面的T3/T细胞受体复合物由四种糖蛋白组成:相对分子质量(Mr)为40,000 - 50,000(40 - 50K)的α链、β链(37 - 45K)、γ链(25K)和δ链(20K)。T3的α链和β链已被鉴定为克隆型T细胞受体,但在功能上T3/T细胞受体链似乎形成一个单一的复合物:针对20K T3成分的单克隆抗体对正常人T淋巴细胞具有促有丝分裂作用,且在较高浓度下,抗克隆型和抗20K试剂会阻断T细胞功能。最近,赞德斯等人表明,用高浓度抗原孵育人T辅助细胞克隆会消除抗原特异性增殖,并诱导T3从细胞表面消失。因此,T3/T细胞受体复合物由两个可变亚基,即与抗原相互作用的T3α链和β链,以及单态性的20K/25K T3链组成。最近,有人推测存在第五种多肽链,即未糖基化的T3ε链。在此我们证实确实存在一条20K的ε链。根据N端氨基酸测序、肽图谱分析以及用抗T3 - δ和抗T3 - ε抗体进行的免疫印迹分析判断,T3ε链在一级结构上与T3δ链不同。用内切糖苷酶F处理后发现两条具有相同氨基末端的非糖基化T3δ多肽主链(16K和14K)。连同之前的脉冲追踪实验,这一观察结果表明14K T3多肽是由16K T3前体通过分子C端附近的蛋白水解加工产生的。