Jensen J P, Bates P W, Yang M, Vierstra R D, Weissman A M
Laboratory of Immune Cell Biology, National Cancer Institute, Bethesda, Maryland 20892-1152, USA.
J Biol Chem. 1995 Dec 22;270(51):30408-14. doi: 10.1074/jbc.270.51.30408.
Two very closely related human E2 ubiquitin conjugating enzymes, UbfH5B and UbcH5C, have been identified. These enzymes are products of distinct genes and are 88-89% identical in amino acid sequence to the recently described human E2, UbcH5 (now designated UbcH5A), UbcH5A-C are homologous to a family of five ubiquitin conjugating enzymes from Arabidopsis thaliana, AtUBC8-12. They are also closely related to Saccharomyces cerevisiae ScUBC4 and ScUBC5, which are involved in the stress response, and play a central role in the targeting of short-lived regulatory proteins for degradation. mRNAs encoding UbcH5A-C were co-expressed in all cell lines and tissues evaluated, with UbcH5C transcripts generally expressed at the highest levels. Analysis of Southern blots suggests that there are likely to be other related members of this family. Both UbcH5B and UbcH5C form thiol ester adducts with ubiquitin, and have activities similar to UbcH5A and AtUBC8 in the conjugation of ubiquitin to target proteins in the presence of the human ubiquitin protein ligase E6-AP. These results establish the existence of a highly conserved, and widely expressed, family of human ubiquitin conjugating enzymes.
已鉴定出两种密切相关的人类E2泛素缀合酶，即UbfH5B和UbcH5C。这些酶是不同基因的产物，其氨基酸序列与最近描述的人类E2、UbcH5（现命名为UbcH5A）有88 - 89%的同一性，UbcH5A - C与拟南芥的五个泛素缀合酶家族AtUBC8 - 12同源。它们也与酿酒酵母的ScUBC4和ScUBC5密切相关，ScUBC4和ScUBC5参与应激反应，并在靶向降解短命调节蛋白中起核心作用。编码UbcH5A - C的mRNA在所有评估的细胞系和组织中共同表达，其中UbcH5C转录本通常表达水平最高。Southern印迹分析表明该家族可能还有其他相关成员。UbcH5B和UbcH5C都与泛素形成硫酯加合物，并且在人泛素蛋白连接酶E6 - AP存在的情况下，在将泛素缀合到靶蛋白方面具有与UbcH5A和AtUBC8相似的活性。这些结果证实了一个高度保守且广泛表达的人类泛素缀合酶家族的存在。
