Ito Y, Abe J, Yoshino K, Takeda T, Kohsaka T
Department of Allergy and Immunology, National Children's Medical Research Center, Tokyo, Japan.
J Immunol. 1995 Jun 1;154(11):5896-906.
We previously reported that the Gram-negative bacterium Yersinia pseudotuberculosis produces a superantigen (YPM, Y. pseudotuberculosis-derived mitogen) that expands T cells bearing V betas 3, 9, 13.1, and 13.2 in an MHC class II-dependent manner. Based on the previously determined N-terminal 23 amino acids of YPM (T-D-Y-D-N-T-L-N-S-I-P-S-L-R-I-P-N-I-A-T-Y-T-G- (one-letter code)), we cloned the ypm gene and analyzed the nucleotide sequence. The gene encodes a 151-amino acid protein with a 20-amino acid signal peptide at its N terminus. The recombinant YPM expressed by the cloned gene exerted a mitogenic activity on human PBMC at a concentration of approximately 1 pg/ml. T cells bearing V beta 13.3 were preferentially expanded as well as T cells bearing the same V beta repertoires stimulated by native YPM. T cells were stimulated by the recombinant YPM in the presence of either fixed or unfixed HLA class II-transfected mouse fibroblasts. Furthermore, sequence diversity in the junctional region of the TCR beta-chain containing the V beta 3 element could be observed after stimulation by the recombinant YPM. These results indicate that YPM belongs to the category of superantigens and should be included as a novel member. The amino acid sequence of the mature protein showed no significant homology to other superantigens derived from Gram-positive bacteria such as Staphylococcus aureus and Streptococcus pyogenes. This observation, together with the substantially smaller m.w. suggest that ypm must have evolved from a different ancestral gene.
我们先前报道，革兰氏阴性菌假结核耶尔森氏菌产生一种超抗原（YPM，源自假结核耶尔森氏菌的丝裂原），该超抗原以MHC II类依赖性方式使携带Vβ3、9、13.1和13.2的T细胞扩增。基于先前确定的YPM的N端23个氨基酸（T-D-Y-D-N-T-L-N-S-I-P-S-L-R-I-P-N-I-A-T-Y-T-G-（单字母编码）），我们克隆了ypm基因并分析了核苷酸序列。该基因编码一个151个氨基酸的蛋白质，其N端有一个20个氨基酸的信号肽。克隆基因表达的重组YPM以约1 pg/ml的浓度对人外周血单核细胞发挥促有丝分裂活性。携带Vβ13.3的T细胞以及由天然YPM刺激的携带相同Vβ谱系的T细胞优先扩增。在固定或未固定的HLA II类转染小鼠成纤维细胞存在下，重组YPM刺激T细胞。此外，重组YPM刺激后可观察到含有Vβ3元件的TCRβ链连接区的序列多样性。这些结果表明YPM属于超抗原类别，应作为一个新成员纳入。成熟蛋白的氨基酸序列与源自革兰氏阳性菌如金黄色葡萄球菌和化脓性链球菌的其他超抗原没有显著同源性。这一观察结果，连同其明显较小的分子量，表明ypm一定是从一个不同的祖先基因进化而来的。
