Aristarkhov A, Eytan E, Moghe A, Admon A, Hershko A, Ruderman J V
Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 1996 Apr 30;93(9):4294-9. doi: 10.1073/pnas.93.9.4294.
Ubiquitin-dependent proteolysis of the mitotic cyclins A and B is required for the completion of mitosis and entry into the next cell cycle. This process is catalyzed by the cyclosome, an approximately 22S particle that contains a cyclin-selective ubiquitin ligase activity, E3-C, that requires a cyclin-selective ubiquitin carrier protein (UBC) E2-C. Here we report the purification and cloning of E2-C from clam oocytes. The deduced amino acid sequence of E2-C indicates that it is a new UBC family member. Bacterially expressed recombinant E2-C is active in in vitro cyclin ubiquitination assays, where it exhibits the same substrate specificities seen with native E2-C. These results demonstrate that E2-C is not a homolog of UBC4 or UBC9, proteins previously suggested to be involved in cyclin ubiquitination, but is a new UBC family member with unique properties.
有丝分裂周期蛋白A和B的泛素依赖性蛋白水解作用是完成有丝分裂并进入下一个细胞周期所必需的。这个过程由细胞周期体催化，细胞周期体是一种约22S的颗粒，它含有一种周期蛋白选择性泛素连接酶活性，即E3-C，该活性需要一种周期蛋白选择性泛素载体蛋白（UBC）E2-C。在此我们报道了从蛤蚌卵母细胞中纯化和克隆E2-C。E2-C推导的氨基酸序列表明它是UBC家族的一个新成员。细菌表达的重组E2-C在体外周期蛋白泛素化测定中具有活性，在该测定中它表现出与天然E2-C相同的底物特异性。这些结果表明E2-C不是先前认为参与周期蛋白泛素化的UBC4或UBC9的同源物，而是具有独特性质的UBC家族新成员。
