The human pathogen Pseudomonas aeruginosa uses the pqs quorum sensing system to coordinate the production of its broad spectrum of virulence factors to facilitate colonization and infection of its host. Hereby, the enzyme PqsD is a virulence related quorum sensing signal synthase that catalyzes the central step in the biosynthesis of the Pseudomonas quinolone signals HHQ and PQS. We developed a library of cysteine reactive chemical probes with an alkyne handle for fluorescence tagging and report the selective and highly sensitive in vitro labelling of the active site cysteine of this important enzyme. Interestingly, only one type of probe, with a reactive α-chloroacetamide was capable of covalently reacting with the active site. We demonstrated the potential of our probes in a competitive labelling platform where we screened a library of synthetic HHQ and PQS analogues with heteroatom replacements and found several inhibitors of probe binding that may represent promising scaffolds for the development of customized PqsD inhibitors as well as a chemical toolbox to investigate the activity and active site specificity of the enzyme.
人类病原体假单胞菌利用pqs群体感应系统来协调其广谱毒力因子的产生,以促进其寄主的定居和感染。在此,酶PqsD是一个与毒力相关的群体感应信号合成酶,它催化了假单胞菌喹啉信号HHQ和PQS的生物合成中的中心步骤。我们开发了一系列含有炔基手柄的半胱氨酸反应性化学探针,用于荧光标记,并报告了对这一重要酶的活性位点半胱氨酸的选择性和高灵敏度的体外标记。有趣的是,只有一种带有反应性α-氯乙酰胺的探针能够与活性位点形成共价键。我们展示了我们的探针在竞争性标记平台中的潜力,我们筛选了一系列合成HHQ和PQS类似物的库,其中包括一些抑制探针结合的化合物,可能代表了用于定制PqsD抑制剂开发的有前景的支架,以及一种用于研究该酶的活性和活性位点特异性的化学工具箱。