Deciphering the roles of promiscuous enzymes in the defense against electrophiles and oxidative stress in Staphylococcus aureus

金黄色葡萄球菌（Staphylococcus aureus）是一种重要的人类病原菌，在感染、细胞代谢或抗生素治疗过程中，它必须与活性氧、亲电物质（ROS、RES）和次卤酸（HOX）科普。作为防御机制，S.金黄色葡萄球菌利用低分子量硫醇杆菌硫醇（BSH）和几种解毒酶和抗氧化酶，其由基于硫醇的氧化还原传感器控制并且通常响应于多种氧化还原信号。在此之前，我们已经探讨了氧化还原敏感调节因子HypR、MhqR、QsrR和GbaA的作用机制和功能，它们是S.金黄色。醌敏感MhqR和QsrR阻遏物调节多种双加氧酶和醌/偶氮还原酶，其赋予对醌、抗生素和氧化剂的抗性。然而，这种混杂解毒酶的生理作用和底物特异性在很大程度上是未知的。本项目旨在阐明混杂的glycoproteinases/dioxygenases和quinone/azo reductases的生理功能及其在氧化和亲电胁迫下的存活、抗性和持久性中的作用。金黄色。我们假设S.金黄色葡萄球菌采用具有广泛特异性的混杂酶，主要防御特异性应激物，例如亲电子的甲基乙二醛或醌类，其干扰硫醇-氧化还原稳态，导致二次ROS形成。因此，亲电体解毒途径配备有还原酶，如醌/偶氮还原酶，以介导对多种氧化还原信号的抗性，包括ROS、HOX和ROS生成抗微生物剂。我们进一步假设，ROS，HOX或RES导致巯基氧化的glycoproteinase-III HchA，这是转化为氧化还原敏感的分子伴侣，以保护细胞蛋白对氧化蛋白质聚集。WP（1）将阐明导致S.金黄色。WP（2）将研究QsrR和MhqR调节子在S.金黄色。QsrR和MhqR调节子对抗生素耐药SCV、持留细胞和L型存活的作用是进一步的研究问题。WP（3）将集中于对巯基胁迫响应最强的SACOL 2588 -2589操纵子的功能表征，该操纵子编码富含Cys的蛋白和小的8.8 kDa DUF 896（UPF 0291）蛋白。总之，这个项目将揭示新的生存机制，使适应多个氧化还原信号，遇到的S。金黄色葡萄球菌在感染和抗生素治疗提供了新的治疗方法，以对抗MRSA感染的设计线索。

Staphylococcus aureus is a major human pathogen, which has to cope with reactive oxygen and electrophile species (ROS, RES) and hypohalous acids (HOX) during infection, cellular metabolism or antibiotics treatment. As defense mechanisms, S. aureus utilizes the low molecular weight thiol bacillithiol (BSH) and several detoxification and antioxidant enzymes, which are controlled by thiol-based redox sensors and often respond to multiple redox signals. Previously, we have explored the mechanisms and functions of the redox-sensing regulators HypR, MhqR, QsrR and GbaA, which are important defense mechanisms under infections in S. aureus. The quinone-sensing MhqR and QsrR repressors regulate multiple dioxygenases and quinone/azo reductases, which confer resistance against quinones, antibiotics and oxidants. However, the physiological roles and substrate specificities of such promiscuous detoxification enzymes are largely unknown. In this project, we aim to elucidate the physiological functions of promiscuous glyoxalases/dioxygenases and quinone/azo reductases and their roles in survival, resistance and persistence under oxidative and electrophile stress in S. aureus. We hypothesize that S. aureus employs promiscuous enzymes with broad specificities, to defend mainly against the specific stressor, e.g. electrophilic methylglyoxal or quinones, which disturb the thiol-redox homeostasis, leading to secondary ROS formation. Thus, electrophile detoxification pathways are equipped with reducing enzymes, such as quinone/azo reductases to mediate resistance against multiple redox signals, including ROS, HOX and ROS-generating antimicrobials. We further hypothesize that ROS, HOX or RES lead to thiol-oxidation of the glyoxalase-III HchA, which is converted to a redox-sensitive chaperone to protect cellular proteins against oxidative protein aggregation. WP (1) will elucidate the BSH-dependent and BSH-independent glyoxalase pathways for detoxification of the toxic electrophile methyglyoxal, causing cytoplasmic acidification in S. aureus. WP (2) will investigate the temporal dynamics, cross-talks and functions of the QsrR and MhqR regulons in protection against quinones and oxidants in S. aureus. The role of the QsrR and MhqR regulons for the survival of antibiotic resistant SCVs, persister cells and L-forms are further research questions. WP (3) will focus on the functional characterization of the most strongly thiol-stress responsive SACOL2588-2589 operon, which encodes a Cys-rich protein and a small 8.8 kDa DUF896 (UPF0291) protein. Altogether, this project will uncover novel survival mechanisms enabling the adaptation towards multiple redox signals, encountered by S. aureus during infections and antibiotic treatments providing leads for the design of novel therapeutics to combat MRSA infections.