Qi Chao, Li De-Feng, Feng Lei, Hou Yanjie, Sun Hui, Wang Da-Cheng, Liu Wei
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2015 Nov 3;5:16056. doi: 10.1038/srep16056.
Ubiquitination is a post-translational modification that is involved in myriad cellar regulation and disease pathways. The ubiquitin-conjugating enzyme (E2) is an important player in the ubiquitin transfer pathway. Although many E2 structures are available, not all E2 families have known structures, and three-dimensional structures from fungal organisms other than yeast are lacking. We report here the crystal structure of UbcA1, which is a novel ubiquitin-conjugating enzyme identified from the edible and medicinal mushroom Agrocybe aegerita and displays potential antitumor properties. The protein belongs to the Ube2w family and shows similar biochemical characteristics to human Ube2w, including monomer-dimer equilibrium in solution, α-NH2 ubiquitin-transfer activity and a mechanism to recognize backbone atoms of intrinsically disordered N-termini in substrates. Its structure displays a unique C-terminal conformation with an orientation of helix α3 that is completely different from the reported E2 structures but similar to a recently reported NMR ensemble of Ube2w. A mutagenesis study on this novel enzyme revealed that an intact C-terminus is significant for protein dimerization and enzymatic activity. As the first crystallized full-length protein of this family, UbcA1 may supersede the truncated X-ray structure of Ube2w (PDB entry 2A7L) as the representative structure of the Ube2w family.
泛素化是一种翻译后修饰，参与众多细胞调控和疾病途径。泛素结合酶（E2）是泛素转移途径中的重要参与者。尽管有许多E2结构可供使用，但并非所有E2家族都有已知结构，并且缺乏来自酵母以外的真菌生物体的三维结构。我们在此报告UbcA1的晶体结构，它是从食用和药用蘑菇杨树菇中鉴定出的一种新型泛素结合酶，具有潜在的抗肿瘤特性。该蛋白属于Ube2w家族，与人类Ube2w具有相似的生化特性，包括溶液中的单体 - 二聚体平衡、α - NH2泛素转移活性以及识别底物中内在无序N端主链原子的机制。其结构显示出独特的C端构象，螺旋α3的取向与报道的E2结构完全不同，但与最近报道的Ube2w的NMR集合相似。对这种新型酶的诱变研究表明，完整的C端对蛋白质二聚化和酶活性很重要。作为该家族第一个结晶的全长蛋白，UbcA1可能取代Ube2w的截短X射线结构（PDB条目2A7L）作为Ube2w家族的代表性结构。
