Hemler M E, Jacobson J G, Strominger J L
J Biol Chem. 1985 Dec 5;260(28):15246-52.
The very late antigen complexes VLA-1 and VLA-2 which appear on long-term activated human T cells have been characterized with respect to 1) subunit arrangement, 2) location of monoclonal antibody (MAb) binding sites, 3) carbohydrate content, and 4) protein homology. Cross-linking experiments showed that the VLA-1 complex is a heterodimer composed of an Mr 210,000 subunit (alpha 1) in acid-labile association with an Mr 130,000 subunit (beta). The VLA-2 complex is a heterodimer with an Mr 165,000 subunit (alpha 2) in base-labile association with the Mr 130,000 beta subunit. The subunits of VLA-1 (alpha 1 beta) and VLA-2 (alpha 2 beta) each appear to be arranged with 1:1 stoichiometry. The MAb A-1A5 has been shown to bind to an epitope on the common beta subunit, consistent with its recognition of both the VLA-1 and VLA-2 heterodimers. On the other hand, MAb TS2/7 bound to an epitope of the alpha 1 subunit, thus explaining the specific recognition of the VLA-1 heterodimer by TS2/7. Digestion of the alpha 1, alpha 2, and beta subunits with neuraminidase and with endoglycosidase F revealed that each subunit contains substantial sialic acid and N-linked carbohydrate. By one-dimensional peptide mapping, the alpha 1, alpha 2, and beta subunits were shown to be highly nonhomologous with respect to each other, although each subunit from different T cell sources appeared highly homologous if not identical.
出现在长期活化的人T细胞上的极晚期抗原复合物VLA-1和VLA-2已在以下方面得到表征：1）亚基排列，2）单克隆抗体（MAb）结合位点的位置，3）碳水化合物含量，以及4）蛋白质同源性。交联实验表明，VLA-1复合物是一种异二聚体，由一个分子量为210,000的亚基（α1）与一个分子量为130,000的亚基（β）以酸不稳定的方式结合而成。VLA-2复合物是一种异二聚体，其分子量为165,000的亚基（α2）与分子量为130,000的β亚基以碱不稳定的方式结合。VLA-1（α1β）和VLA-2（α2β）的亚基似乎均以1:1的化学计量比排列。已证明单克隆抗体A-1A5与共同β亚基上的一个表位结合，这与其对VLA-1和VLA-2异二聚体的识别一致。另一方面，单克隆抗体TS2/7与α1亚基的一个表位结合，从而解释了TS2/7对VLA-1异二聚体的特异性识别。用神经氨酸酶和内切糖苷酶F对α1、α2和β亚基进行消化后发现，每个亚基都含有大量的唾液酸和N-连接碳水化合物。通过一维肽图谱分析表明，α1、α2和β亚基彼此之间高度不同源，尽管来自不同T细胞来源的每个亚基即使不完全相同也显得高度同源。
