Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology submitted time 2016-05-15
Abstract： The cyclic nucleotide-binding (CNB)-like protein (CNB-L) from Brucella abortus shares sequence homology with CNB domain-containing proteins. We determined the crystal structure of CNB-L at 2.0 angstrom resolution in the absence of its C-terminal helix and nucleotide. The 3D structure of CNB-L is in a twofold symmetric form. Each protomer shows high structure similarity to that of cGMP-binding domain-containing proteins, and likely mimics their nucleotide-free conformation. A key residue, Glu17, mediates the dimerization and prevents binding of cNMP to the canonical ligand-pocket. The structurally observed dimer of CNB-L is stable in solution, and thus is likely to be biologically relevant. (C) 2015 Elsevier Inc. All rights reserved.
Peer Review Status:
Awaiting Review
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology submitted time 2016-05-12
Dong, Jing
Zhang, Yong
Zhang, Yu
Li, Rui
Deng, Xuming
Dong, Jing
Chen, Yutao
Wang, Quan
Li, Xuemei
Niu, Xiaodi
Yang, Cheng
Abstract： Toxic ribosome-inactivating proteins abolish cell viability by inhibiting protein synthesis. Ricin, a member of these lethal proteins, is a potential bioterrorism agent. Despite the grave challenge posed by these toxins to public health, post-exposure treatment for intoxication caused by these agents currently is unavailable. In this study, we report the identification of baicalin extracted from Chinese herbal medicine as a compound capable of inhibiting the activity of ricin. More importantly, post-exposure treatment with baicalin significantly increased the survival of mice poisoned by ricin. We determined the mechanism of action of baicalin by solving the crystal structure of its complex with the A chain of ricin (RTA) at 2.2 angstrom resolution, which revealed that baicalin interacts with two RTA molecules at a novel binding site by hydrogen bond networks and electrostatic force interactions, suggesting its role as molecular glue of the RTA. Further biochemical and biophysical analyses validated the amino acids directly involved in binding the inhibitor, which is consistent with the hypothesis that baicalin exerts its inhibitory effects by inducing RTA to form oligomers in solution, a mechanism that is distinctly different from previously reported inhibitors. This work offers promising leads for the development of therapeutics against ricin and probably other ribosome-inactivating proteins.
Peer Review Status:Awaiting Review
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