Virtual Screening of Peptide and Peptidomimetic Fragments Targeted to Inhibit Bacterial Dithiol Oxidase DsbA
作者:Wilko Duprez、Prabhakar Bachu、Martin J. Stoermer、Stephanie Tay、Róisín M. McMahon、David P. Fairlie、Jennifer L. Martin
DOI:10.1371/journal.pone.0133805
日期:——
Antibacterial drugs with novel scaffolds and new mechanisms of action are desperately needed to address the growing problem of antibiotic resistance. The periplasmic oxidative folding system in Gram-negative bacteria represents a possible target for anti-virulence antibacterials. By targeting virulence rather than viability, development of resistance and side effects (through killing host native microbiota) might be minimized. Here, we undertook the design of peptidomimetic inhibitors targeting the interaction between the two key enzymes of oxidative folding, DsbA and DsbB, with the ultimate goal of preventing virulence factor assembly. Structures of DsbB - or peptides - complexed with DsbA revealed key interactions with the DsbA active site cysteine, and with a hydrophobic groove adjacent to the active site. The present work aimed to discover peptidomimetics that target the hydrophobic groove to generate non-covalent DsbA inhibitors. The previously reported structure of a Proteus mirabilis DsbA active site cysteine mutant, in a non-covalent complex with the heptapeptide PWATCDS, was used as an in silico template for virtual screening of a peptidomimetic fragment library. The highest scoring fragment compound and nine derivatives were synthesized and evaluated for DsbA binding and inhibition. These experiments discovered peptidomimetic fragments with inhibitory activity at millimolar concentrations. Although only weakly potent relative to larger covalent peptide inhibitors that interact through the active site cysteine, these fragments offer new opportunities as templates to build non-covalent inhibitors. The results suggest that non-covalent peptidomimetics may need to interact with sites beyond the hydrophobic groove in order to produce potent DsbA inhibitors.
迫切需要具有新型骨架和新作用机制的抗菌药物来解决日益严重的抗生素抗药性问题。革兰氏阴性菌中的周质氧化折叠系统代表了抗毒力抗菌药物可能的靶点。通过针对毒力而非生存能力,可能最大限度地减少耐药性的发展和副作用(通过杀死宿主的原生微生物群)。在此,我们进行了设计,旨在针对氧化折叠的两个关键酶DsbA和DsbB之间的相互作用,设计出肽模拟物抑制剂,最终目标是阻止毒力因子组装。DsbB或肽与DsbA复合物的结构揭示了与DsbA活性位点半胱氨酸以及活性位点附近的一个疏水性凹槽的关键相互作用。目前的工作目标是发现靶向疏水性凹槽的肽模拟物,以生成非共价DsbA抑制剂。先前报道的变形杆菌DsbA活性位点半胱氨酸突变体的结构,在非共价复合物中与七肽PWATCDS结合,被用作计算机模拟筛选肽模拟物片段库的模板。得分最高的片段化合物及其九个衍生物被合成,并评估其DsbA结合和抑制作用。这些实验发现了在毫摩尔浓度下具有抑制活性的肽模拟物片段。尽管相对于通过活性位点半胱氨酸相互作用的大分子共价肽抑制剂而言,这些片段的效力较弱,但它们提供了作为构建非共价抑制剂模板的新机会。结果表明,非共价肽模拟物可能需要与疏水性凹槽以外的位点相互作用,才能产生强效的DsbA抑制剂。