Wang Chongyuan, Zhu Yuwei, Caceres Tamar B, Liu Lei, Peng Junhui, Wang Junchen, Chen Jiajing, Chen Xuwen, Zhang Zhiyong, Zuo Xiaobing, Gong Qingguo, Teng Maikun, Hevel Joan M, Wu Jihui, Shi Yunyu
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Anhui 230027, China.
Chemistry and Biochemistry Department, Utah State University, 0300 Old Main Hill, Logan, UT 84322, USA.
Structure. 2014 May 6;22(5):756-68. doi: 10.1016/j.str.2014.03.003. Epub 2014 Apr 10.
Trypanosoma brucei protein arginine methyltransferase 7 (TbPRMT7) exclusively generates monomethylarginine (MMA), which directs biological consequences distinct from that of symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA). However, determinants controlling the strict monomethylation activity are unknown. We present the crystal structure of the TbPRMT7 active core in complex with S-adenosyl-L-homocysteine (AdoHcy) and a histone H4 peptide substrate. In the active site, residues E172, E181, and Q329 hydrogen bond the guanidino group of the target arginine and align the terminal guanidino nitrogen in a position suitable for nucleophilic attack on the methyl group of S-adenosyl-L-methionine (AdoMet). Structural comparisons and isothermal titration calorimetry data suggest that the TbPRMT7 active site is narrower than those of protein arginine dimethyltransferases, making it unsuitable to bind MMA in a manner that would support a second turnover, thus abolishing the production of SDMA and ADMA. Our results present the structural interpretations for the monomethylation activity of TbPRMT7.
布氏锥虫蛋白精氨酸甲基转移酶7（TbPRMT7）仅生成单甲基精氨酸（MMA），其引导的生物学效应不同于对称二甲基精氨酸（SDMA）和不对称二甲基精氨酸（ADMA）。然而，控制严格单甲基化活性的决定因素尚不清楚。我们展示了与S-腺苷-L-高半胱氨酸（AdoHcy）和组蛋白H4肽底物形成复合物的TbPRMT7活性核心的晶体结构。在活性位点，E172、E181和Q329残基与靶精氨酸的胍基形成氢键，并将末端胍基氮排列在适合对S-腺苷-L-甲硫氨酸（AdoMet）甲基进行亲核攻击的位置。结构比较和等温滴定量热法数据表明，TbPRMT7活性位点比蛋白精氨酸二甲基转移酶的活性位点更窄，使其无法以支持二次周转的方式结合MMA，从而消除了SDMA和ADMA的产生。我们的结果给出了TbPRMT7单甲基化活性的结构解释。
