Langton Michelle, Pandelia Maria E
Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02453, United States.
ACS Omega. 2020 Jun 28;5(27):16772-16778. doi: 10.1021/acsomega.0c01762. eCollection 2020 Jul 14.
HBx is the smallest gene product of the Hepatitis B virus (HBV) and an oncogenic stimulus in chronic infections leading to liver disease. HBx interacts and interferes with numerous cellular processes, but its modes of action remain poorly understood. It has been invoked that HBx employs nucleotide hydrolysis to regulate molecular pathways or protein-protein interactions. In the present study, we reinvestigate the (d)NTP hydrolysis of recombinant HBx to explore its potential as a biochemical probe for antiviral studies. For our investigations, we employed existing soluble constructs (i.e., GST-HBx, MBP-HBx) and engineered new fusion proteins (i.e., DsbC-HBx, NusA-HBx), which are shown to serve as better systems for research. We performed mutational scanning of the computationally predicted NTP-binding domain, which includes residues associated with clinical cases. Steady-state and end-point activity assays, in tandem with mass-spectrometric analyses, reveal that the observed hydrolysis of all alleged HBx substrates, ATP, dATP, and GTP, is contingent on the presence of the GroEL chaperone, which preferentially copurifies as a contaminant with GST-HBx and MBP-HBx. Collectively, our findings provide new technical standards for recombinant HBx studies and reveal that nucleotide hydrolysis is not an operant mechanism by which HBx contributes to viral HBV carcinogenesis.
乙肝病毒X蛋白(HBx)是乙型肝炎病毒(HBV)最小的基因产物,是慢性感染导致肝脏疾病的致癌刺激因素。HBx可与众多细胞过程相互作用并产生干扰,但其作用方式仍知之甚少。有人提出,HBx利用核苷酸水解来调节分子途径或蛋白质-蛋白质相互作用。在本研究中,我们重新研究重组HBx的(脱氧)核糖核苷三磷酸水解,以探索其作为抗病毒研究生化探针的潜力。在我们的研究中,我们使用了现有的可溶性构建体(即谷胱甘肽S-转移酶-HBx、麦芽糖结合蛋白-HBx)并构建了新的融合蛋白(即二硫键异构酶C-HBx、NusA-HBx),结果表明这些构建体可作为更好的研究系统。我们对通过计算预测的NTP结合结构域进行了突变扫描,该结构域包括与临床病例相关的残基。稳态和终点活性测定与质谱分析相结合,结果表明,所有所谓的HBx底物(ATP、dATP和GTP)的水解均取决于伴侣蛋白GroEL的存在,而GroEL优先作为污染物与谷胱甘肽S-转移酶-HBx和麦芽糖结合蛋白-HBx共纯化。总体而言,我们的研究结果为重组HBx研究提供了新的技术标准,并表明核苷酸水解不是HBx促成HBV病毒致癌作用的有效机制。
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