Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. The enzyme has two structure states: non-active opened structure and active...Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. The enzyme has two structure states: non-active opened structure and active closed structure. During change from non-active opened structure to active closed structure, the protein loop connecting domain α to domain α/β becomes bent remarkablely, which results in two domains closed up, and binding pocket reduce obviously. Setting about from the inactive-open X-ray structure, applying the method of molecular dynamic simulation, putting the ligand in the active-pocket, we carry out a dynamic simulation in the CVFF force-field for the entire system. The structures obstained are more approximately to the active-close X-ray structures, it proves that the rigid movement of the domains is arouse by the inducing effect of the ligand molecules.展开更多
背景与目的:不育α基序结构域和组氨酸/天冬氨酸残基双联体结构域包涵蛋白1(sterile alpha motif and histidine/aspartic acid domain-containing protein 1,SAMHD1)具有抑制多种肿瘤细胞生长的作用,但其调节肝细胞癌(hepatocellular c...背景与目的:不育α基序结构域和组氨酸/天冬氨酸残基双联体结构域包涵蛋白1(sterile alpha motif and histidine/aspartic acid domain-containing protein 1,SAMHD1)具有抑制多种肿瘤细胞生长的作用,但其调节肝细胞癌(hepatocellular carcinoma,HCC)细胞增殖的作用及机制尚未见报道。探究SAMHD1调控p27的表达对HCC细胞Huh7的增殖、凋亡和细胞周期的影响。方法:首先通过蛋白质印迹法(Western blot)检测正常肝细胞和不同类型HCC细胞中SAMHD1的表达情况。利用基因修饰技术构建过表达SAMHD1、dNTP酶活性位点突变体(SAMHD1-D207N)和磷酸化位点突变体(SAMHD1-T592E)的重组质粒,然后利用四甲基偶氮唑蓝(methyl thiazolyl tetrazolium,MTT)法检测过表达SAMHD1及其突变体或siRNA干扰沉默SAMHD1对HCC细胞增殖的影响,采用流式细胞术检测细胞周期与细胞凋亡情况。在癌症基因组图谱(The Cancer Genome Atlas,TCGA)数据库中分析SAMHD1和p27表达的相关性。结果:HCC细胞中SAMHD1表达上调,过表达SAMHD1、SAMHD1-D207N和SAMHD1-T592E可以抑制Huh7细胞增殖,细胞周期停滞在G1/G0期;相反,干扰SAMHD1后细胞增殖加快,细胞周期停滞在G2/M期。机制研究表明,SAMHD1上调细胞周期蛋白激酶抑制因子p27的表达。在HCC组织中,p27的表达与SAMHD1表达呈正相关。结论:过表达SAMHD1可以上调p27的表达,导致细胞周期停滞在G1/G0期,从而抑制HCC细胞增殖,这种抑制作用不依赖于其dNTP酶活性和磷酸化修饰。展开更多
文摘Pyrimidine nucleoside phosphorylase(PYNP) catalyzes the reversible phosphorolysis of pyrimidines in the nucleotide synthesis salvage pathway. The enzyme has two structure states: non-active opened structure and active closed structure. During change from non-active opened structure to active closed structure, the protein loop connecting domain α to domain α/β becomes bent remarkablely, which results in two domains closed up, and binding pocket reduce obviously. Setting about from the inactive-open X-ray structure, applying the method of molecular dynamic simulation, putting the ligand in the active-pocket, we carry out a dynamic simulation in the CVFF force-field for the entire system. The structures obstained are more approximately to the active-close X-ray structures, it proves that the rigid movement of the domains is arouse by the inducing effect of the ligand molecules.
