Modular organisation of inducer recognition and allostery in the tetracycline repressor.
Modular organisation of inducer recognition and allostery in the tetracycline repressor.
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DOI：
10.2210/pdb6fts/pdb
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发表时间：
2016-06
期刊：
影响因子：
5.4
通讯作者：
S. Werten;J. Schneider;G. Palm;W. Hinrichs
中科院分区：
文献类型：
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作者：
S. Werten;J. Schneider;G. Palm;W. Hinrichs
四环素抑制物(TetR)的诱导是由于抗生素依赖改变DNA结合结构域在启动子相关的抑制物二聚体中的相对位置，但这种变构效应的关键决定因素仍未得到很好的表征。有趣的是，以前对四环素相互作用位点的突变分析显示，残留亲和力和诱导倾向之间缺乏相关性，这表明与抗生素接触的一些残基主要起配基识别和保留作用，而其他残基则需要传递变构信号。在这里，我们通过对点突变N82A、H100A、T103A和E147A与诱导剂5a，6-脱水四环素的络合物的结晶学分析，为这些观察提供了结构基础。结合现有的功能数据，这四个结构表明α6和α7之间的区域向结合位点的触发式移动在分子内通信过程中起着决定性的作用。与此形成鲜明对比的是，结合腔内的残基对变构机制的影响很小，甚至没有影响。这种几乎完全的配体识别和变构的物理分离将允许不同的TetR样阻遏物结合新的效应物，同时现有的诱导机制保持不变。因此，这里描述的模块化可能是广泛和高度多样化的抑制子类进化成功的关键因素。数据库结构数据可在蛋白质数据库中获得，登录号为5FKK、5FKL、5FKM、5FKN和5FKO。
Induction of the tetracycline repressor (TetR) results from antibiotic-dependent changes in the relative positioning of the DNA-binding domains within the promoter-associated repressor dimer, but the key determinants of this allosteric effect remain poorly characterised. Intriguingly, previous mutational analyses of the tetracycline-interacting site revealed a lack of correlation between residual affinity and induction propensity, suggesting that some of the residues in contact with the antibiotic primarily act in ligand recognition and retention, whereas others are required to transmit the allosteric signal. Here, we provide a structural basis for these observations via crystallographic analysis of the point mutants N82A, H100A, T103A and E147A in complex with the inducer 5a,6-anhydrotetracycline. In conjunction with the available functional data, the four structures demonstrate that a trigger-like movement of the region between helices α6 and α7 towards and into the binding site plays a decisive role in the intramolecular communication process. In sharp contrast, residues lining the binding cavity proper have little or no influence on the allosteric mechanism as such. This nearly complete physical separation of ligand recognition and allostery will have allowed diverging TetR-like repressors to bind novel effectors while the existing induction mechanism remained intact. Consequently, the modularity described here may have been a key factor in the evolutionary success of the widespread and highly diversified repressor class. Database Structural data are available in the Protein Data Bank under the accession numbers 5FKK, 5FKL, 5FKM, 5FKN and 5FKO.