Choi-Miura N H, Sano Y, Oda E, Nakano Y, Tobe T, Yanagishita T, Taniyama M, Katagiri T, Tomita M
Department of Physiological Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo.
J Biochem. 1995 Feb;117(2):400-7. doi: 10.1093/jb/117.2.400.
Plasmapheresis with a dextran sulfate column is a treatment for patients with hypercholesteremia. When proteins bound to the column during the treatment were fractionated to prepare some known proteins, we found a 57 kDa glycoprotein designated GP57 which showed a new N-terminal amino acid sequence. Western-blot analysis of human plasma revealed that only a 120 kDa protein, GP120, reacted with anti-GP57 antibody. Since GP120 and GP57 had an identical N-terminal amino acid sequence, GP120 is probably the intact form of GP57. The isoelectric point of GP120 was 6.8. N-Glycanase treatment decreased the molecular weight of GP120 by 15 kDa. Neuraminidase and O-glycanase, however, did not affect the molecular weight. Amino acid sequence analyses of the lysylendopeptidase digest of GP120 revealed significant homology to the heavy chains of inter-alpha-trypsin inhibitor (ITI) family. Since GP120 showed no bikunin sequence, and chondroitinase treatment and alkaline treatment of GP120 did not affect its molecular weight, we concluded that GP120 was not a complex with bikunin. We designated GP120 as IHRP (ITI heavy chain-related protein).
使用硫酸葡聚糖柱进行血浆置换是治疗高胆固醇血症患者的一种方法。在治疗过程中，当与柱子结合的蛋白质被分离以制备一些已知蛋白质时，我们发现了一种名为GP57的57 kDa糖蛋白，它显示出一种新的N端氨基酸序列。对人血浆进行的蛋白质印迹分析表明，只有一种120 kDa的蛋白质GP120与抗GP57抗体发生反应。由于GP120和GP57具有相同的N端氨基酸序列，GP120可能是GP57的完整形式。GP120的等电点为6.8。N-糖苷酶处理使GP120的分子量降低了15 kDa。然而，神经氨酸酶和O-糖苷酶对分子量没有影响。对GP120的赖氨酰内肽酶消化产物进行的氨基酸序列分析显示，与α-胰蛋白酶抑制剂（ITI）家族的重链具有显著同源性。由于GP120没有显示出比库宁序列，并且对GP120进行硫酸软骨素酶处理和碱性处理不会影响其分子量，我们得出结论，GP120不是与比库宁形成的复合物。我们将GP120命名为IHRP（ITI重链相关蛋白）。
