Zhao Wentao, Zhou Yang, Li Caiyi, Bi Yucong, Wang Keyun, Ye Mingliang, Li Haitao
MOE Key Laboratory of Protein Sciences, Beijing Frontier Research Center for Biological Structure, School of Medicine, Tsinghua University, Beijing, 100084, China.
CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China.
Cell Insight. 2023 Mar 31;2(3):100090. doi: 10.1016/j.cellin.2023.100090. eCollection 2023 Jun.
Histidine methylation serves as an intriguing strategy to introduce altered traits of target proteins, including metal ion chelation, histidine-based catalysis, molecular assembly, and translation regulation. As a newly identified histidine methyltransferase, METTL9 catalyzes N1-methylation of protein substrates containing the "His-x-His" motif (HxH, x denotes small side chain residue). Here our structural and biochemical studies revealed that METTL9 specifically methylates the second histidine of the "HxH" motif, while exploiting the first one as a recognition signature. We observed an intimate engagement between METTL9 and a pentapeptide motif, where the small "x" residue is embedded and confined within the substrate pocket. Upon complex formation, the N3 atom of histidine imidazole ring is stabilized by an aspartate residue such that the N1 atom is presented to S-adenosylmethionine for methylation. Moreover, METTL9 displayed a feature in preferred consecutive and "C-to-N" directional methylation of tandem "HxH" repeats that exist in many METTL9 substrates. Collectively, our work illustrates the molecular design of METTL9 in N1-specific methylation of the broadly existing "HxH" motifs, highlighting its importance in histidine methylation biology.
组氨酸甲基化是一种引人关注的策略，可用于引入靶蛋白的改变特性，包括金属离子螯合、基于组氨酸的催化、分子组装和翻译调控。作为一种新鉴定的组氨酸甲基转移酶，METTL9催化含有“His-x-His”基序（HxH，x表示小侧链残基）的蛋白质底物的N1-甲基化。在这里，我们的结构和生化研究表明，METTL9特异性地甲基化“HxH”基序的第二个组氨酸，同时将第一个组氨酸用作识别特征。我们观察到METTL9与一个五肽基序之间存在紧密结合，其中小的“x”残基嵌入并限制在底物口袋内。在复合物形成时，组氨酸咪唑环的N3原子由一个天冬氨酸残基稳定，使得N1原子呈现给S-腺苷甲硫氨酸进行甲基化。此外，METTL9在许多METTL9底物中存在的串联“HxH”重复序列的优先连续和“C到N”方向甲基化方面表现出一个特征。总的来说，我们的工作阐明了METTL9在广泛存在的“HxH”基序的N1特异性甲基化中的分子设计，突出了其在组氨酸甲基化生物学中的重要性。
