RNA Therapeutics Institute, University of Massachusetts Medical School, 368 Plantation St, Worcester, MA 01605, USA.
RNA Therapeutics Institute, Howard Hughes Medical Institute, University of Massachusetts Medical School, 368 Plantation St, Worcester, MA 01605, USA.
Sci Rep. 2017 Apr 20;7(1):969. doi: 10.1038/s41598-017-01186-5.
Eubacterial ribosomal large-subunit methyltransferase H (RlmH) methylates 23S ribosomal RNA pseudouridine 1915 (Ψ1915), which lies near the ribosomal decoding center. The smallest member of the SPOUT superfamily of methyltransferases, RlmH lacks the RNA recognition domain found in larger methyltransferases. The catalytic mechanism of RlmH enzyme is unknown. Here, we describe the structures of RlmH bound to S-adenosyl-methionine (SAM) and the methyltransferase inhibitor sinefungin. Our structural and biochemical studies reveal catalytically essential residues in the dimer-mediated asymmetrical active site. One monomer provides the SAM-binding site, whereas the conserved C-terminal tail of the second monomer provides residues essential for catalysis. Our findings elucidate the mechanism by which a small protein dimer assembles a functionally asymmetric architecture.
细菌核糖体大亚基甲基转移酶 H（RlmH）甲基化位于核糖体解码中心附近的 23S 核糖体 RNA 假尿嘧啶 1915（Ψ1915）。RlmH 是 SPOUT 甲基转移酶超家族中最小的成员，缺乏在较大的甲基转移酶中发现的 RNA 识别结构域。RlmH 酶的催化机制尚不清楚。在这里，我们描述了 RlmH 与 S-腺苷甲硫氨酸（SAM）和甲基转移酶抑制剂 sinefungin 结合的结构。我们的结构和生化研究揭示了二聚体介导的不对称活性位点中的催化必需残基。一个单体提供了 SAM 结合位点，而第二个单体的保守 C 端尾巴提供了催化所必需的残基。我们的发现阐明了小蛋白二聚体组装功能不对称结构的机制。
