PPC结构域广泛存在于分泌型细菌胞外蛋白酶的C端，目前为止其功能还未明确，缺乏系统研究。本项目以PPC结构域为研究对象，重点研究来源于不同环境细菌的PPC结构域吸附功能的多样性及其分子机制。首先，通过生物信息学手段对PPC结构域的序列进行系统分析，解析PPC结构域序列结构的多样性及其规律。然后，比较不同细菌分泌的具有PPC结构域的同家族蛋白酶的酶学特性、底物特异性及其PPC结构域吸附功能的差异，揭示不同环境来源的PPC结构域吸附功能的多样性及其存在于蛋白酶C端的生态学意义。进而通过基因突变、超微结构观察和动力学模拟，分析造成PPC结构域吸附功能差异的关键位点和作用机理，从而阐明PPC结构域吸附功能多样性的分子机制，并为开发PPC结构域在底物改性中的新用途奠定基础。最后,对不同吸附功能的PPC结构域间进行基因置换，比较重组酶与野生酶的活性变化，为构建新结构、新功能的蛋白酶提供理论依依据。

PPC domain is widely present in the C terminus of bacterial extracellular protease. However, its function has not been fully elucidated. In this project, our aim is to determine the affinity function diversity of PPC domain and its molecular mechanism. First, we will determine the sequence divesity of PPC domains by analyzing the sequences and structures of PPC domains with bioinformatics methods. Second, we will determine the affinity function diversity and significant differences of PPC domains of M4 metalloproteases from various bacteria species. These studies include enzymatic properties，substrate speicificity of different metalloproteases and binding functions of PPC domains to different protein substrates. Third, we will determine key residues and mode of interaction that cause the difference in the binding function of PPC domains by mutagenesis, molecular dynamic simulation and observation of ultramicrostructure, therefore elucidate the molecular mechanism of affinity function diversity of PPC domains,and developing the new use of PPC domain. Finally, we will generate chimeric proteases with novel structure and characterize the function. A gene-swapping technique will be performed, which swaps different functional PPC domains from one protease to another. Results from these studies will provide critical understanding on molecular mechanism of affinity function diversity and ecological significance of PPC domain.