Fossum S, Mallett S, Barclay A N
MRC Cellular Immunology Unit, Sir William Dunn School of Pathology, University of Oxford, GB.
Eur J Immunol. 1991 Mar;21(3):671-9. doi: 10.1002/eji.1830210320.
The MRC OX-47 monoclonal antibody recognizes a membrane antigen present at low levels on many lymphocytes but whose expression is markedly increased on activation with mitogens. cDNA clones for the OX-47 antigen were isolated from an expression library and the protein sequence deduced. It contains a leader sequence giving a mature protein of 251 amino acids with a single putative transmembrane region, a cytoplasmic domain of 40 amino acids and an extracellular domain of 187 amino acids that contained two immunoglobulin-like domains. The putative transmembrane sequence includes a glutamic acid residue within the hydrophobic sequence. The presence of acidic residues within the hydrophobic sequence of transmembrane sequences usually indicates association with other polypeptides and this is predicted for the OX-47 antigen. A sequence of 37 amino acids that included all the transmembrane region was identical to that of the chicken HT7 antigen present on endothelium in brain and erythroblasts. The level of protein sequence identity in the Ig-like domains was lower but HT7 is almost certainly the chicken homologue of the rat OX-47 antigen. The ligand and function of the molecule are unknown. In addition to lymphoblasts the OX-47 antigen was localized on a variety of other cell types including various immature cells, endothelia and cells with excitable membranes.
MRC OX - 47单克隆抗体识别一种膜抗原，该抗原在许多淋巴细胞上低水平存在，但在有丝分裂原激活后其表达会显著增加。从一个表达文库中分离出了OX - 47抗原的cDNA克隆，并推导了其蛋白质序列。它包含一个前导序列，产生一个由251个氨基酸组成的成熟蛋白，有一个单一的假定跨膜区域、一个40个氨基酸的胞质结构域和一个187个氨基酸的胞外结构域，该胞外结构域包含两个免疫球蛋白样结构域。假定的跨膜序列在疏水序列中有一个谷氨酸残基。跨膜序列疏水序列中存在酸性残基通常表明与其他多肽相关，OX - 47抗原也被预测如此。一段包含所有跨膜区域的37个氨基酸的序列与存在于脑内皮细胞和成红细胞中的鸡HT7抗原的序列相同。免疫球蛋白样结构域中的蛋白质序列同一性水平较低，但HT7几乎肯定是大鼠OX - 47抗原的鸡同源物。该分子的配体和功能尚不清楚。除了淋巴母细胞外，OX - 47抗原还定位于多种其他细胞类型，包括各种未成熟细胞、内皮细胞和具有可兴奋膜的细胞。
