杀多菌广谱裂解酶的结构基础与作用机制研究

日益严重的细菌耐药已成为全球公共健康领域的一项重大挑战。噬菌体裂解酶因具有天然的进化优势和极低的耐药性，是近十年来备受关注的天然抗菌分子。然而裂解酶的临床开发和应用却受限于其较强的宿主特异性。得益于嵌合裂解酶高通量筛选技术的发展和多国科研人员的长期探索，广谱裂解酶近几年取得了一些进展。但由于缺乏对现有广谱裂解酶静态、动态结构与杀菌机理关系的精确认识，以及对其底物识别机制的深入研究，广谱裂解酶的设计仍存在很大的盲目性和偶然性。本项目拟以申请人实验室构建的目前最广谱的裂解酶ClyR（杀菌谱覆盖了几乎所有种类的链球菌、肠球菌和金黄色葡萄球菌）为模式分子，用生物化学、结构生物学和体外进化等方法鉴定ClyR的识别底物，解析ClyR及其与底物复合物的结构，揭示其杀多菌的结构基础和作用机制。本研究不仅能为发展新型广谱裂解酶提供理论指导，而且能为抗菌药物的筛选提供潜在的靶标，具有非常重要的理论和实际意义。

The increasing antimicrobial resistance is one of the most urgent threats to public health worldwide. Due to their many advantages, including evolution with the host bacteria and rare resistance, bacteriophage lysins, produced by phages in the late phase of infection cycle to digest bacterial cell wall for the release of progeny virions, have showed great potential as anti-infectives and attracted much attentions during the past decade. However, the clinical development and application of lysins was hampered by their narrow host ranges. Benefitting from the rapid improvement of the screening technologies for chimeric lysins and the great efforts from researchers worldwide, several lysins with broad host range have been developed. However, due to the less understanding between the structural characteristics as well as the binding substrates of lysins with broad host range and their broad killing capacity, the designing and engineering of lysins with broad host range was still blindness. In this study, the novel chimeric lysin, ClyR (showing broad lytic activity against most streptococci, including S. pneumoniae, S. pyogenes, S. suis, S. uberis, S. agalactiae, S. dysgalactiae, S. mutans, S. equi and susceptible staphylococci and enterococci, developed by high throughput screening method in our laboratory previously) was used as a model molecule to study the relationship between structure and function in lysins with broad host range. We will study the binding substrate of ClyR, resolution the structures of ClyR, ClyR/substrate complex to discover the structural characteristics and multiple-killing mechanisms of ClyR. This study will not only provide guidelines for developing new lysins with broad host-range, but also provide potent targets for new antibacterial drug development.