Perturbance of enzyme function by blocking dimer interface formation: Novel route to specific antibiotics

tRNA修饰酶，tRNA-鸟嘌呤转糖基酶（Tgt），构成了一个推定的目标，新的选择性抗生素对志贺氏菌。基于Tgt与tRNA复合物的几种晶体结构，提出了Tgt同源二聚体的形成。可以在非降解条件下研究蛋白质复合物的非共价nanoESI质谱法证实了溶液中的二聚体寡聚化状态及其与底物tRNA的2：1结合化学计量。引入点突变以使蛋白质-蛋白质二聚体界面不稳定。酶动力学揭示了这些突变变体的催化活性降低，推测与二聚体的不稳定有关，如通过非共价质谱法和X射线晶体学进一步证明的。延伸的活性位点抑制剂渗透到二聚体界面区域扰乱蛋白质-蛋白质接触的相互作用几何形状。这些抑制剂将进一步发展成为唯一的界面结合剂，防止二聚体形成，从而阻断蛋白质功能。或者，虚拟和实验筛选将被应用于发现新的界面粘合剂。将进行连接适当的二硫化物与工程化到表面暴露位置的Cys残基的拴系方法，以识别界面区域中的弱结合剂。然后将这些进行优化，以产生有效的界面粘合剂。

The tRNA modifying enzyme, tRNA-guanine transglycosylase (Tgt), constitutes a putative target for new selective antibiotics against Shigella bacteria. Based on several crystal structures of Tgt in complex with tRNA the formation of a Tgt homodimer was suggested. Non-covalent nanoESI mass spectrometry that can study protein complexes under non-degrading conditions confirms the dimeric oligomerisation state in solution and 2:1 binding stoichiometry with its Substrate tRNA. Point mutations were introduced to destabilize the protein-protein dimer interface. Enzyme kinetics reveal a reduced catalytic activity of these mutated variants supposedly related to the destabilization of the dimer as further evidenced by both, non-covalent mass spectrometry and X-ray crystallography. Extended active site inhibitors penetrating into the dimer interface region perturb the interaction geometry of the protein-protein contact. These inhibitors will be further developed into sole interface binders preventing dimer formation and thus blocking protein function. Alternatively, virtual and experimental screening will be applied to discover novel interface binders. A tethering approach connecting appropriate disulfides with Cys residues engineered into surface-exposed positions will be performed to identify weak binders in the interface region. These will then be optimized to result in potent interface binders.