Uzan G, Frachet P, Lajmanovich A, Prandini M H, Denarier E, Duperray A, Loftus J, Ginsberg M, Plow E, Marguerie G
Institut National de la Santé et de la Recherche Médicale Unité 217, Département de Recherches Fondamentales, Grenoble, France.
Eur J Biochem. 1988 Jan 15;171(1-2):87-93. doi: 10.1111/j.1432-1033.1988.tb13762.x.
Platelet glycoprotein (GP) IIb is one of the two subunits of the common platelet adhesion receptor, GPIIb-IIIa. The isolation, characterization and sequencing of cDNA clones encoding for the two polypeptide chains of GPIIb are described. A number of clones were isolated from lambda gt11 libraries constructed with mRNA from an erythroleukemic cell line, HEL, and human megakaryocytes. Two of these clones, lambda IIb1, from HEL cells, and lambda IIb2, from megakaryocytes, cross-hybridized and were selected for detailed analysis. The identification of these as authentic GPIIb clones was based on immunological criteria and confirmed by the presence of nucleotide sequences in each insert encoding for known protein sequences of platelet GPIIb. These clones contained inserts of 1.54 kb and 1.39 kb, respectively, with an overlapping sequence of 801 bp. The nucleotide sequence of the overlapping region was identical indicating that HEL cells produce a protein closely related, if not identical, to platelet GPIIb. The determined nucleotide sequence of two inserts included a coding sequence for 648 amino acid residues, a TAG stop codon and 185 nucleotides of 3' non-coding sequence followed by a poly(A) tail. The coding sequence contained a portion of the heavy chain, the junction between the heavy and light chains and the entire light chain including a potential transmembrane-spanning domain and a short cytoplasmic tail. When these cDNA were used to probe for GPIIb mRNA, a single mRNA species of 3.9 kb was identified in both HEL cells and human megakaryocytes. A comparison of the deduced amino acid sequence for GPIIb with those of the alpha subunit of the vitronectin and the fibronectin receptors revealed extensive homologies. These homologies further establish that GPIIb-IIIa from platelets, together with the vitronectin and the fibronectin receptors, are members of a supergene family of adhesion receptors with a recognition specificity for Arg-Gly-Asp amino acid sequences.
血小板糖蛋白（GP）IIb是常见血小板黏附受体GPIIb-IIIa的两个亚基之一。本文描述了编码GPIIb两条多肽链的cDNA克隆的分离、特性鉴定及测序。从用红白血病细胞系HEL和人巨核细胞的mRNA构建的λgt11文库中分离出了多个克隆。其中两个克隆，来自HEL细胞的λIIb1和来自巨核细胞的λIIb2，相互交叉杂交并被选作详细分析。根据免疫学标准将这些克隆鉴定为真正的GPIIb克隆，并通过每个插入片段中编码血小板GPIIb已知蛋白质序列的核苷酸序列的存在得到证实。这些克隆分别包含1.54 kb和1.39 kb的插入片段，重叠序列为801 bp。重叠区域的核苷酸序列相同，表明HEL细胞产生的一种蛋白质即使与血小板GPIIb不完全相同，也密切相关。两个插入片段的测定核苷酸序列包括一个编码648个氨基酸残基的编码序列、一个TAG终止密码子和185个3'非编码序列核苷酸，后面跟着一个聚腺苷酸尾巴。编码序列包含重链的一部分、重链和轻链之间的连接以及整个轻链，包括一个潜在的跨膜结构域和一个短的细胞质尾巴。当用这些cDNA探测GPIIb mRNA时，在HEL细胞和人巨核细胞中都鉴定出了一种3.9 kb的单一mRNA物种。将推导的GPIIb氨基酸序列与玻连蛋白和纤连蛋白受体的α亚基的氨基酸序列进行比较，发现了广泛的同源性。这些同源性进一步证实，血小板的GPIIb-IIIa与玻连蛋白和纤连蛋白受体一起，是对精氨酸-甘氨酸-天冬氨酸氨基酸序列具有识别特异性的黏附受体超基因家族的成员。
