Cryo-EM structure of the tetracycline resistance protein TetM in complex with a translating ribosome at 3.9-Å resolution
Cryo-EM structure of the tetracycline resistance protein TetM in complex with a translating ribosome at 3.9-Å resolution
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DOI：
10.1073/pnas.1501775112
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发表时间：
2015-04-28
影响因子：
11.1
通讯作者：
Wilson, Daniel N.
中科院分区：
文献类型：
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作者：
Arenz, Stefan;Nguyen, Fabian;Wilson, Daniel N.
核糖体保护蛋白(RPP)通过与核糖体结合并从其结合部位追逐药物来增强对四环素的耐药性。目前的RPP作用模型是从7.2埃到16埃分辨率的RPP与空洞或非翻译核糖体结合的结构推导而来的。在这里，我们提出了一个冷冻电子显微镜重建的RPP TetM与平移核糖体在3.9埃分辨率的复合体。该结构揭示了TetM与核糖体的接触，包括TetM保守的和功能关键的C末端延伸与小亚基解码中心独特的A1492和A1493核苷酸展开构象之间的相互作用。这一决议使我们能够毫不含糊地模拟TetM结构域IV中包含环III的氨基酸残基的侧链，揭示酪氨酸残基Y506和Y507并不负责先前提出的药物释放，而是负责似乎稳定环III构象的因子内接触。相反，环III末端的Pro509直接位于四环素结合部位，在那里它与16S rRNA的核苷酸C1054相互作用，因此RPP作用使用Pro509而不是Y506/Y507直接从核糖体中排出和释放四环素。
Ribosome protection proteins (RPPs) confer resistance to tetracycline by binding to the ribosome and chasing the drug from its binding site. Current models for RPP action are derived from 7.2- to 16-angstrom resolution structures of RPPs bound to vacant or nontranslating ribosomes. Here we present a cryo-electron microscopy reconstruction of the RPP TetM in complex with a translating ribosome at 3.9-angstrom resolution. The structure reveals the contacts of TetM with the ribosome, including interaction between the conserved and functionally critical C-terminal extension of TetM with a unique splayed conformation of nucleotides A1492 and A1493 at the decoding center of the small subunit. The resolution enables us to unambiguously model the side chains of the amino acid residues comprising loop III in domain IV of TetM, revealing that the tyrosine residues Y506 and Y507 are not responsible for drug-release as suggested previously but rather for intrafactor contacts that appear to stabilize the conformation of loop III. Instead, Pro509 at the tip of loop III is located directly within the tetracycline binding site where it interacts with nucleotide C1054 of the 16S rRNA, such that RPP action uses Pro509, rather than Y506/Y507, to directly dislodge and release tetracycline from the ribosome.