The human ubiquitin carrier protein E2(Mr = 17,000) is homologous to the yeast DNA repair gene RAD6.
The human ubiquitin carrier protein E2(Mr = 17,000) is homologous to the yeast DNA repair gene RAD6.
复制标题
人类泛素载体蛋白E2(Mr = 17,000)与酵母DNA修复基因RAD6同源。
作者：
R. Schneider;C. Eckerskorn;F. Lottspeich;M. Schweiger
通过在泛素琼脂糖上的共价亲和层析从人胎盘中纯化泛素缀合系统的组分。与从兔网织红细胞和红细胞或酿酒酵母获得的E2制剂相反，胎盘E2制剂缺乏E2（Mr = 14，000）和E2（Mr = 20，000），这两种制剂在催化泛素向组蛋白的连接酶非依赖性转移方面都是独特的。采用一种新技术，在SDS电泳和硝酸纤维素印迹后检测E2蛋白的泛素载体功能。通过用简并寡核苷酸筛选从人cDNA文库中分离E2（Mr = 17，000）的cDNA，所述简并寡核苷酸的序列基于从E2（Mr = 17，000）肽获得的部分氨基酸序列。序列分析表明，在人E2（Mr = 17，000）和由酵母DNA修复基因RAD6编码的蛋白质的一级序列中有69%的同一性，该基因最近被证明是酵母中的E2物种。人E2（Mr = 17，000）和酵母DNA修复酶之间的这种高度相似性提示了除了泛素载体活性之外的重要的共同结构约束或作用，因为在酵母中，这种功能本身不一定依赖于一级结构的高度保守性。
Components of the ubiquitin conjugating system were purified from human placenta by covalent affinity chromatography on ubiquitin sepharose. In contrast to E2 preparations obtained from rabbit reticulocytes and erythrocytes or Saccharomyces cerevisiae, the placental E2 preparation lacks E2(Mr = 14,000) and E2(Mr = 20,000) which are both unique in catalysing the ligase‐independent transfer of ubiquitin to histones. A novel technique was employed to detect ubiquitin carrier function of the E2 proteins after SDS‐electrophoresis and blotting to nitrocellulose. A cDNA of E2(Mr = 17,000) was isolated from a human cDNA library by screening with a degenerate oligonucleotide whose sequence was based on a partial amino acid sequence obtained from an E2(Mr = 17,000) peptide. Sequence analysis demonstrated an identity of 69% in the primary sequence of human E2(Mr = 17,000) and the protein encoded by the yeast DNA repair gene RAD6, which was recently shown to be an E2 species in yeast. Such a high degree of similarity between the human E2(Mr = 17,000) and the yeast DNA repair enzyme is suggestive of important common structural constraints or roles in addition to ubiquitin carrier activity, since in yeast this function itself is not necessarily dependent on high conservation of primary structure.