分类： 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间： 2016-05-12
摘要： Papain-like protease (PLpro) of coronaviruses (CoVs) carries out proteolytic maturation of non-structural proteins that play a role in replication of the virus and performs deubiquitination of host cell factors to scuttle antiviral responses. Avian infectious bronchitis virus (IBV), the causative agent of bronchitis in chicken that results in huge economic losses every year in the poultry industry globally, encodes a PLpro. The substrate specificities of this PLpro are not clearly understood. Here, we show that IBV PLpro can degrade Lys(48)- and Lys(63)-linked polyubiquitin chains to monoubiquitin but not linear polyubiquitin. To explain the substrate specificities, we have solved the crystal structure of PLpro from IBV at 2.15-angstrom resolution. The overall structure is reminiscent of the structure of severe acute respiratory syndrome CoV PLpro. However, unlike the severe acute respiratory syndrome CoV PLpro that lacks blocking loop (BL) 1 of deubiquitinating enzymes, the IBV PLpro has a short BL1-like loop. Access to a conserved catalytic triad consisting of Cys(101), His(264), and Asp(275) is regulated by the flexible BL2. A model of ubiquitin-bound IBV CoV PLpro brings out key differences in substrate binding sites of PLpros. In particular, P3 and P4 subsites as well as residues interacting with the beta-barrel of ubiquitin are different, suggesting different catalytic efficiencies and substrate specificities. We show that IBV PLpro cleaves peptide substrates KKAG-7-amino-4-methylcoumarin and LRGG-7-amino-4-methylcoumarin with different catalytic efficiencies. These results demonstrate that substrate specificities of IBV PLpro are different from other PLpros and that IBV PLpro might target different ubiquitinated host factors to aid the propagation of the virus.
分类： 生物学 >> 生物物理学 >> 肿瘤学 提交时间： 2016-05-11
Hu, Shi
Guo, Huaizu
Qian, Weizhu
Hou, Sheng
Li, Bohua
Guo, Yajun
Hu, Shi
Guo, Huaizu
Qian, Weizhu
Hou, Sheng
Li, Bohua
Guo, Yajun
Hu, Shi
Sun, Yuna
Rao, Zihe
Hu, Shi
Sun, Yuna
Rao, Zihe
Lou, Zhiyong
Hu, Shi
摘要： Human epidermal growth factor receptors (HERs or ErbBs) play crucial roles in numerous cellular processes. ErbB2 is a key member of ErbB family, and its overexpression is recognized as a frequent molecular abnormality. In cancer, this overexpression correlates with aggressive disease and poor patient outcomes. Dimer-dependent phosphorylation is a key event for the signal transduction of ErbBs. However, the molecular mechanism of the dimerization of ErbB2 remains elusive. In the present work, we report the homodimer architecture of the ErbB2 extracellular domain (ECD) which is unique compared with other dimer-models of ErbBs. The structure of the ErbB2 ECD homodimer represents a "back to head" interaction, in which a protruding beta-hairpin arm in domain II of one ErbB2 protomer is inserted into a C-shaped pocket created by domains I-III of the adjacent ErbB2 protomer. This dimerized architecture and its impact on the phosphorylation of ErbB2 intracellular domain were further verified by a mutagenesis study. We also elucidated the different impacts of two clinically administered therapeutic antibodies, trastuzumab and pertuzumab, on ErbB2 dimerization. This information not only provides an understanding of the molecular mechanism of ErbBs dimerization but also elucidates ErbB2-targeted therapy at the molecular level.
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