Publications by authors named "Mei-Hui Hou"

3 Publications

  • Page 1 of 1

Crystal structure and functional implication of a bacterial cyclic AMP-AMP-GMP synthetase.

Nucleic Acids Res 2021 May;49(8):4725-4737

Institute of New Drug Development, China Medical University, Taichung 406, Taiwan.

Mammalian cyclic GMP-AMP synthase (cGAS) and its homologue dinucleotide cyclase in Vibrio cholerae (VcDncV) produce cyclic dinucleotides (CDNs) that participate in the defense against viral infection. Recently, scores of new cGAS/DncV-like nucleotidyltransferases (CD-NTases) were discovered, which produce various CDNs and cyclic trinucleotides (CTNs) as second messengers. Here, we present the crystal structures of EcCdnD, a CD-NTase from Enterobacter cloacae that produces cyclic AMP-AMP-GMP, in its apo-form and in complex with ATP, ADP and AMPcPP, an ATP analogue. Despite the similar overall architecture, the protein shows significant structural variations from other CD-NTases. Adjacent to the donor substrate, another nucleotide is bound to the acceptor binding site by a non-productive mode. Isothermal titration calorimetry results also suggest the presence of two ATP binding sites. GTP alone does not bind to EcCdnD, which however binds to pppApG, a possible intermediate. The enzyme is active on ATP or a mixture of ATP and GTP, and the best metal cofactor is Mg2+. The conserved residues Asp69 and Asp71 are essential for catalysis, as indicated by the loss of activity in the mutants. Based on structural analysis and comparison with VcDncV and RNA polymerase, a tentative catalytic pathway for the CTN-producing EcCdnD is proposed.
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May 2021

Tannic acid suppresses SARS-CoV-2 as a dual inhibitor of the viral main protease and the cellular TMPRSS2 protease.

Am J Cancer Res 2020 1;10(12):4538-4546. Epub 2020 Dec 1.

Graduate Institute of Biomedical Sciences, College of Medicine, China Medical University Taichung 40402, Taiwan.

The cell surface protein TMPRSS2 (transmembrane protease serine 2) is an androgen-responsive serine protease important for prostate cancer progression and therefore an attractive therapeutic target. Besides its role in tumor biology, TMPRSS2 is also a key player in cellular entry by the SARS-CoV viruses. The COVID-19 pandemic caused by the coronavirus SARS-CoV-2 has resulted in huge losses in socio-economy, culture, and human lives for which safe and effective cures are highly demanded. The main protease (M/3CL) of SARS-CoV-2 is a critical enzyme for viral propagation in host cells and, like TMPRSS2, has been exploited for treatment of the infectious disease. Numerous natural compounds abundant in common fruits have been suggested with anti-coronavirus infection in the previous outbreaks of SARS-CoV. Here we show that screening of these compounds identified tannic acid a potent inhibitor of both SARS-CoV-2 M and TMPRSS2. Molecular analysis demonstrated that tannic acid formed a thermodynamically stable complex with the two proteins at a K of 1.1 mM for M and 1.77 mM for TMPRSS2. Tannic acid inhibited the activities of the two proteases with an IC of 13.4 mM for M and 2.31 mM for TMPRSS2. M protein. Consistently, functional assays using the virus particles pseudotyped (Vpp) of SARS-CoV2-S demonstrated that tannic acid suppressed viral entry into cells. Thus, our results demonstrate that tannic acid has high potential of developing anti-COVID-19 therapeutics as a potent dual inhibitor of two independent enzymes essential for SARS-CoV-2 infection.
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December 2020

Structural basis of SARS-CoV-2 main protease inhibition by a broad-spectrum anti-coronaviral drug.

Am J Cancer Res 2020 1;10(8):2535-2545. Epub 2020 Aug 1.

Institute of New Drug Development, China Medical University Taichung 40402, Taiwan.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or 2019 novel coronavirus (2019-nCoV), took tens of thousands of lives and caused tremendous economic losses. The main protease (M) of SARS-CoV-2 is a potential target for treatment of COVID-19 due to its critical role in maturation of viral proteins and subsequent viral replication. Conceptually and technically, targeting therapy against M is similar to target therapy to treat cancer. Previous studies show that GC376, a broad-spectrum dipeptidyl M inhibitor, efficiently blocks the proliferation of many animal and human coronaviruses including SARS-CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), porcine epidemic diarrhea virus (PEDV), and feline infectious peritonitis virus (FIPV). Due to the conservation of structure and catalytic mechanism of coronavirus main protease, repurposition of GC376 against SARS-CoV-2 may be an effective way for the treatment of COVID-19 in humans. To validate this conjecture, the binding affinity and IC value of M with GC376 was determined by isothermal titration calorimetry (ITC) and fluorescence resonance energy transfer (FRET) assay, respectively. The results showed that GC376 binds to SARS-CoV-2 M tightly (K = 1.6 μM) and efficiently inhibit its proteolytic activity (IC = 0.89 μM). We also elucidate the high-resolution structure of dimeric SARS-CoV-2 M in complex with GC376. The cocrystal structure showed that GC376 and the catalytic Cys145 of M covalently linked through forming a hemithioacetal group and releasing a sulfonic acid group. Because GC376 is already known as a broad-spectrum antiviral medication and successfully used in animal, it will be a suitable candidate for anti-COVID-19 treatment.
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August 2020