猪繁殖与呼吸综合征病毒聚合酶nsp9的结构与功能研究

猪繁殖与呼吸综合征病毒（PRRSV）传染性很强，给畜牧业造成重大的危害和经济损失。PRRSV病毒是正链RNA病毒，变异快，导致病毒疫苗的研制步履维艰，尚无特别有效的治疗和预防方法。核酸聚合酶（nsp9)是此类病毒蛋白中最保守的蛋白之一，对病毒的生存至关重要。nsp9与严重危害人类健康的冠状病毒的核酸聚合酶同属一个蛋白大家族，具有相似的结构域，但同源性很低。.nsp9含有一个核苷酸转移酶结构域以及RNA依赖的RNA聚合酶结构域，但目前nsp9或同源物的结构还没有被解析。本项目将从结构生物学和分子生物学等角度解析nsp9家族及其与核苷酸类似物、DNA/RNA复合物的结构，阐明nsp9合成RNA的分子催化机制和结构基础，研究nsp9内部结构域之间的活力调节机制、底物的选择性及其结构与功能的关系，深入探讨nsp9的催化和调控机理，为寻找相互作用的蛋白、筛选抑制剂和药物设计等提供结构基础和指明方向。

Porcine reproductive and respiratory syndrome virus (PRRSV) is highly infectious, seriously harms the livestock and causes significant economic loss. PRRSV, one of the positive-strand RNA viruses, varies rapidly, making the development of viral vaccines very difficult. To date, no effective method for the treatment and prevention of the virus was found. RNA-dependent RNA polymerase (nsp9) is one of the most conserved proteins among the virus proteins, playing vital roles in the virus. The nsp9 shows weak homology with the RNA-dependent RNA polymerase from the coronaviruses which greatly hurt human health, although both proteins belong to a large family with similar domains..The nsp9 contains a newly discovered nidovirus nucleotidyltransferase domain, and an RNA-dependent RNA polymerase domain. Currently, no structures of nsp9 or homology have been solved. Based on our present work, this study would focus on solving the structures of the nsp9 family, and complex structures with nucleoside analogs and DNA/RNA by protein crystallography and molecular biology. The project will uncover the mechanism of the activity regulation between domains of nsp9, substrate selectivity and specificity, the relationship of structure and function, and the mechanism of catalysis and regulation. It will provide a structural basis and a direction for the search of interacting proteins, screening inhibitors, and drug design.