COMPLETE LOCALIZATION OF THE INTRACHAIN DISULFIDE BONDS AND THE N-GLYCOSYLATION POINTS IN THE ALPHA-SUBUNIT OF HUMAN-PLATELET GLYCOPROTEIN-IIB
COMPLETE LOCALIZATION OF THE INTRACHAIN DISULFIDE BONDS AND THE N-GLYCOSYLATION POINTS IN THE ALPHA-SUBUNIT OF HUMAN-PLATELET GLYCOPROTEIN-IIB
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DOI：
10.1042/bj2610561
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发表时间：
1989-07-15
影响因子：
4.1
通讯作者：
GONZALEZRODRIGUEZ, J
中科院分区：
文献类型：
--
作者：
CALVETE, JJ;HENSCHEN, A;GONZALEZRODRIGUEZ, J
糖蛋白IIb(GPIIb)是血小板表面可诱导的纤维蛋白原受体的两个分子成分之一，由两个亚基GPIIbα组成。(114 KDa)和GPIIb.beta。(22.5 kDa)，由一个二硫键连接。对GPIIb进行CNBR切割，再用胰酶或内切酶Lys-C消化部分分离的CNBR多肽，然后对分离片段进行氨基酸和N-端序列分析，我们就可以明确地定位所有未知的二硫键和血小板中的N-糖化点。可以确定，GPIIb中的每个半胱氨酸残基，从α-Cys-56开始，与其氨基酸序列中最近的邻位半胱氨酸以二硫键结合。鉴于Arg-Gly-Asp黏附受体两链α-亚基之间广泛的结构相似性以及半胱氨酸残基在其氨基酸序列中的保守位置，在GPIIb中发现的链内和链间二硫键模式很可能在这些受体的所有两链α-亚基中保守。在血小板GPIIb中发现的N-连接糖基化点与人红白血病细胞GPIIb的cDNA测序后提出的五个N-糖基化天冬酰胺残基相同[Poncz，Eisman，Heindenreich，Silver，Vilaire，Surrey，Schwartz和Bennett(1987)J.Biol]。化学，262,8476-8482]。讨论了GPIIb结构的一些一般特征，如α和β亚基中存在不同的结构域，以及在其外部地形中明确定义的点的识别。
Glycoprotein IIb (GPIIb), one of the two molecular components of the inducible receptor for fibrinogen on the platelet surface, is formed from two subunits, GPIIb.alpha. (114 kDa) and GPIIb.beta. (22.5 kDa), joined by a single disulphide bond. CNBr cleavage of GPIIb, together with tryptic or endoproteinase Lys-C digestion of some of the isolated CNBr peptides, followed by amino acid and N-terminal sequence analysis of the isolated fragments, allowed us to locate unambiguously all the unknown disulphide bonds and the N-glycosylation points in platelet GPIIb. It could be established that each cysteine residue in GPIIb, beginning at .alpha.-Cys-56, is disulphide-bonded to its nearest neighbour in the amino acid sequence. Given the extensive structural similarity among the two-chain .alpha.-subunits of Arg-Gly-Asp adhesion receptors and the conservative positions of cysteine residues in their amino acids sequences, the intrachain and interchain disulphide-bond pattern found here in GPIIb will most probably be conserved in all two-chain .alpha.-subunits of these receptors. The N-linked glycosylation points found here in platelet GPIIb are the same as the five N-glycosylated asparagine residues suggested after cDNA sequencing of human erythroleukaemic-cell GPIIb [Poncz, Eisman, Heindenreich, Silver, Vilaire, Surrey, Schwartz and Bennett (1987) J. Biol. Chem, 262, 8476-8482]. Some of the general features of the structure of GPIIb, such as the existence of distinct domains in the .alpha.- and .beta.-subunits, as well as the identification of well-defined points in its external topography, are discussed.