Haasemann M, Nawratil P, Müller-Esterl W
Institute of Physiological Chemistry and Pathobiochemistry, University of Mainz, Federal Republic of Germany.
Biochem J. 1991 Mar 15;274 ( Pt 3)(Pt 3):899-902. doi: 10.1042/bj2740899.
Human alpha 2-HS glycoprotein and bovine fetuin, abundant proteins of fetal plasma, are structural members of the fetuin family within the cystatin superfamily. They are characterized by the presence of two N-terminally located cystatin-like units and a unique C-terminal sequence segment not present in the other members of the cystatin superfamily. Search for related sequences revealed that the natural inhibitor of the insulin receptor tyrosine kinase [Auberger, Falquerho, Contreres, Pages, Le Cam, Rossi & Le Cam (1989) Cell (Cambridge, Mass.) 58, 631-640] shows sequence similarity to the mammalian fetuins. The sequence identity between rat tyrosine kinase inhibitor, human alpha 2-HS glycoprotein and bovine fetuin is 56 and 60% respectively (percentage of residues in identical positions). The sequence similarity extends over the entire protein structures, except the extreme C-terminal portions. In particular, the number and relative positions of the cysteine residues are invariant among the proteins, suggesting that the characteristic array of linearly arranged and tandemly repeated disulphide loops of the cystatin superfamily is also present in rat tyrosine kinase inhibitor. We conclude that rat tyrosine kinase inhibitor may be classified as a novel member of the mammalian fetuin family.
人α2-HS糖蛋白和牛胎球蛋白是胎儿血浆中的丰富蛋白质，属于胱抑素超家族中胎球蛋白家族的结构成员。它们的特征是存在两个位于N端的胱抑素样结构域以及一个在胱抑素超家族其他成员中不存在的独特C端序列片段。对相关序列的搜索显示，胰岛素受体酪氨酸激酶的天然抑制剂[Auberger, Falquerho, Contreres, Pages, Le Cam, Rossi & Le Cam (1989) Cell (Cambridge, Mass.) 58, 631 - 640]与哺乳动物胎球蛋白具有序列相似性。大鼠酪氨酸激酶抑制剂与人α2-HS糖蛋白和牛胎球蛋白之间的序列同一性分别为56%和60%（相同位置残基的百分比）。序列相似性延伸至整个蛋白质结构，除了极端的C端部分。特别是，这些蛋白质中半胱氨酸残基的数量和相对位置是不变的，这表明胱抑素超家族中线性排列和串联重复的二硫键环的特征排列在大鼠酪氨酸激酶抑制剂中也存在。我们得出结论，大鼠酪氨酸激酶抑制剂可被归类为哺乳动物胎球蛋白家族的一个新成员。
