异柠檬酸脱氢酶家族中一类结构独特的新型蛋白的性质、结构、功能及进化意义研究

异柠檬酸脱氢酶（IDH）是中心代谢中重要看家蛋白，细菌IDH的磷酸化是乙醛酸循环开启的前提，而后者与致病性相关。我们发现IDH家族存在一支未见报道的二聚体NADP-IDH。鲍曼不动杆菌（Ab）等非发酵菌是医院感染的重要病原菌。分析发现虽都是革兰氏阴性细菌，但与大肠杆菌不同，Ab等病原菌都包含了2种NADP-IDH，其中一种就是结构独特的新型二聚体酶（IDH2）。IDH2大都来自病原微生物。因此本项目拟对IDH2进行功能鉴定，解析其晶体结构，揭示其催化机制。进而研究翻译后修饰对IDH2活性的影响，以及对乙醛酸循环开或关的调控。通过比较野生型及IDH2缺失菌株在不同碳源中的生长速率、生物被膜形成结果、细菌毒力、药敏性的差异检测，研究IDH2的生理功能及其在乙酸中具有生长优势的原因，以及揭示IDH的活性、乙醛酸循环的功能性与Ab等非发酵菌耐药性之间的关联。为临床耐药机制研究提供新思路。

Isocitrate dehydrogenase (IDH) is an important housekeeping protein in the central metabolic pathway. Phosphorylation of bacterial IDH is a prerequisite for the initiation of glyoxylate cycle, which is related to the pathogenicity. We found a novel monomeric-like dimeric NADP-IDH in the IDH family. Non-fermentative bacteria such as Acinetobacter baumannii is a primary Gram-negative pathogen in nosocomial infection. Due to the prevalence of the drug resistant A. baumannii, a significant threat has been posed to the clinical anti-infective treatment. Unlike E. coli (a.typical Gram-negative bacteria), A. baumannii and other non-fermentative bacteria encodes two NADP-IDH (AbIDH), one of which stands for this novel dimeric NADP-IDH (IDH2). AbIDH2, together with its counterparts from other important pathogens, group into a new separate clade on the evolutionary tree of IDH protein family. Therefore, this project intends to identify the function of the novel IDH2, determine the crystal structure, and analyze the catalytic mechanism. Furthermore, the effect of post-translational modification on IDH2 activity, and its regulation mechanism on the opening or closing status of the glyoxylate cycle will be explored. Furthermore, the physiological role of IDH2 and the causes for the great growth advantage of A. baumannii on acetate will be announced. The relationships among IDH2 activity, the glyoxylate cycle function and the drug resistance of A. baumannii will be revealed by comparing the growth rate, biofilm formation, bacterial virulence and drug sensitivity of wild-type and IDH2-deficient strains in different carbon sources. This work will provide new strategies for studying the drug resistance mechanism and useful information for clinical treatment.