Acyl-homoserine lactone signal fidelity enforcing mechanism in bacterial communication

 描述（由申请人提供）：由多重耐药微生物引起的感染对治疗细菌感染提出了特殊挑战，因此迫切需要对抗细菌毒力而不加重耐药性的治疗策略。革兰氏阴性细菌使用酰基高丝氨酸内酯介导的群体感应来调节关键生理活动，包括毒力、生物膜形成和毒素产生。细菌 阿勒脱氢酶使用酰基- ACP和S-腺苷-L-甲硫氨酸产生细胞内阿勒自诱导物信号。尽管阿勒合酶的小分子抑制剂在治疗多药耐药细菌感染中作为抗微生物剂具有显著的前景，但设计阿勒合酶特异性抑制剂仍然是一个重大挑战，因为酰基-ACP和SAM都被许多必需的真核酶用作底物。为了确保有效的细菌间通信，信号合成酶如阿勒脱氢酶必须精确地为该细菌产生天然信号，并避免合成非特异性信号（信号保真度）。在这个提议中，我们将研究阿勒合酶如何选择性地识别其天然酰基底物从池的非天然底物，以加强信号保真度在细菌群体感应。特别是，我们将确定阿勒合成中每个酶促步骤对信号保真度的贡献程度。基于我们对鼻疽伯克霍尔德菌BmaI 1阿勒合酶的初步研究，我们推测酰基底物识别主要发生在[酶.酰基底物.SAM]三元复合物上。我们将测试这一假设的阿勒合成酶的广泛阵列。在本申请中提出的三个目标应共同提供关键的见解酰基-ACP底物识别的分子基础的短，中，长链脱氢酶，这将通知阿勒合酶特异性抑制剂的设计。

 DESCRIPTION (provided by applicant): Infections caused by multidrug resistant organisms pose special challenges to treating bacterial infections and therefore therapeutic strategies that combat bacterial virulence without aggravating drug resistance are in great demand. Gram-negative bacteria use acyl- homoserine lactone mediated quorum sensing to regulate key physiological activities that includes virulence, biofilm formation and toxin production. Bacterial AHL synthases use acyl- ACP and S-adenosyl-L- methionine to make intracellular AHL autoinducer signals. Although small molecule inhibitors for AHL synthase enzymes hold significant promise as antimicrobials in treating multidrug resistant bacterial infections, designig AHL synthase specific inhibitors does remain a significant challenge because both acyl-ACP and SAM are used as substrates by many essential eukaryotic enzymes. To ensure efficient interbacterial communication, signal-synthesizing enzymes such as AHL synthases must precisely make the native signal for that bacterium and avoid synthesizing nonspecific signals (signal fidelity). In this proposal, we will investigate how AHL synthase enzymes selectively recognize their native acyl-substrate from a pool of non-native substrates to enforce signal fidelity in bacterial quorum sensing. In particular, we will determine the extent to which each enzymatic step in AHL synthesis contributes to signal fidelity. Based on our preliminary data with Burkholderia mallei BmaI1 AHL synthase, we hypothesize that acyl-substrate recognition predominantly occurs at [Enzyme.acyl-substrate.SAM] ternary complex. We will test this hypothesis for a broad array of AHL synthase enzymes. The three aims proposed in this application should collectively provide key insights into molecular basis of acyl-ACP substrate recognition by short, medium and long-chain synthases, which will inform the design of AHL synthase specific inhibitors.