Suzuki S, Argraves W S, Pytela R, Arai H, Krusius T, Pierschbacher M D, Ruoslahti E
Proc Natl Acad Sci U S A. 1986 Nov;83(22):8614-8. doi: 10.1073/pnas.83.22.8614.
Cells adhere to vitronectin substrates through a cell surface receptor that recognizes an Arg-Gly-Asp sequence in vitronectin. The receptor is a glycoprotein composed of a 150-kDa alpha and a 115-kDa beta subunit. The alpha subunit consists of two disulfide-bonded chains of 125 kDa and 25 kDa. cDNA clones were isolated for the alpha subunit of the vitronectin receptor from a phage lambda gt11 expression library made with RNA from a human fibroblast cell line, IMR-90. The identity of the clones that had been selected from the library based on immunological criteria was verified by comparison of DNA and protein sequences. NH2-terminal sequences were obtained for each of the alpha-subunit chains. The sequence of the 25-kDa chain of the alpha subunit was found in a cDNA clone, and the amino acid sequence deduced from the cDNA establishes the complete amino acid sequence of the 25-kDa chain. This chain contains a membrane-spanning domain as well as a putative intracytoplasmic region that is 32 amino acids long and consists mostly of polar amino acids. Comparison of the cDNA and protein sequences shows that the 25-kDa chain is generated by proteolytic cleavage of an alpha-subunit precursor, the partial sequence of which is contained in the cDNA clones. These clones contain 1910 base pairs of open reading frame and a 3' untranslated sequence. RNA blot hybridization detected one transcript of about 7 kilobases in RNA from fibroblastic and epithelial cells. Together, the cDNA clones cover 4442 bases of this RNA. The alpha-subunit sequence showed strong homology with the sequence of the alpha subunit of fibronectin receptor. Moreover, the NH2-terminal protein sequence of the 125-kDa chain was homologous with the NH2-terminal sequences of two other cell surface proteins, lymphocyte function-associated antigen 1 (LFA-1) and macrophage antigen 1 (Mac-1), which have been implicated as receptors for adhesion proteins of leukocytes. These results establish several of the structural features in the vitronectin receptor and suggest the existence of a superfamily of receptors for cell adhesion proteins.
细胞通过一种细胞表面受体黏附于玻连蛋白底物，该受体可识别玻连蛋白中的精氨酸 - 甘氨酸 - 天冬氨酸序列。该受体是一种糖蛋白，由一个150 kDa的α亚基和一个115 kDa的β亚基组成。α亚基由两条通过二硫键相连的链组成，分别为125 kDa和25 kDa。利用来自人成纤维细胞系IMR - 90的RNA构建噬菌体λgt11表达文库，从中分离出玻连蛋白受体α亚基的cDNA克隆。通过比较DNA和蛋白质序列，验证了基于免疫学标准从文库中筛选出的克隆的身份。获得了α亚基每条链的氨基末端序列。在一个cDNA克隆中发现了α亚基25 kDa链的序列，从该cDNA推导的氨基酸序列确定了25 kDa链的完整氨基酸序列。这条链包含一个跨膜结构域以及一个推测的胞质内区域，该区域长32个氨基酸，主要由极性氨基酸组成。cDNA和蛋白质序列的比较表明，25 kDa链是由α亚基前体经蛋白水解切割产生的，其部分序列包含在cDNA克隆中。这些克隆包含开放阅读框的1910个碱基对和一个3'非翻译序列。RNA印迹杂交在成纤维细胞和上皮细胞的RNA中检测到一条约7千碱基的转录本。这些cDNA克隆一起覆盖了该RNA的4442个碱基。α亚基序列与纤连蛋白受体α亚基的序列具有很强的同源性。此外，12�kDa链的氨基末端蛋白质序列与另外两种细胞表面蛋白——淋巴细胞功能相关抗原1（LFA - 1）和巨噬细胞抗原1（Mac - l）的氨基末端序列同源，这两种蛋白被认为是白细胞黏附蛋白的受体。这些结果确定了玻连蛋白受体的几个结构特征，并提示存在一个细胞黏附蛋白受体超家族。
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