No abstract

Background: Cyclic di-AMP inactivates the potassium transport activity of KtrA. Results: Cyclic di-AMP binding to KrtA induced conformational changes. Conclusion: Cyclic di-AMP selectively binds to the KtrA RCK_C domain and signals the inactivation of potassium transport. Significance: The molecular basis for the role of cyclic di-AMP in potassium channel activity was investigated.

Worldwide, over 170 million people have hepatitis C virus (HCV) infections. [1] Chronic infection with HCV leads to liver diseases such as cirrhosis and hepatocarcinoma and is the major reason of liver transplantation. [2] Currently, the standard treatment for hepatitis C relies on a combination of interferon-a and ribavirin (an immune booster and a general inhibitor of virus replication, respectively) which is associated with serious side effects including hemolytic anaemia, depression, fatigue, flu-like symptoms, and birth defects. [3] The standard of care is frequently ineffective in clearing HCV infections and the virus often survives and thrives even under the treatment.To develop direct-acting antiviral agents for hepatitis C treatment, studies have been focused on the discovery of inhibitors of viral enzymes, specifically nonstructural protein 3 (NS3) serine protease and NS5B RNA-dependent RNA polymerase (RdRp). [4] Last year, new drugs for treating hepatitis C, Telaprevir (Vertex) and Boceprevir (Merck) , which are NS3 serine protease inhibitors, were approved by the U.S. Food and Drug Administration (FDA), and over 30 drug candidates targeting the same protease or NS5B RdRp are currently in clinical trials. [5] Although phase III clinical trials of Telaprevir and Boceprevir showed notable increases in the cure rate, nearly every patient still suffered from at least one side effect of the new therapy. [5b,c, 6] In addition, HCV has strong drug resistance due to its high mutability. Thus, further therapeutic options are urgently needed to treat HCV infections more effectively.The C-terminal two thirds of HCV NS3 forms a helicase, which has the ability to unwind double-stranded DNA (dsDNA) into single-stranded DNA (ssDNA) and is fueled by nucleoside triphosphates (NTPs) hydrolyzed by its NTPase domain. [7] NS3 helicase is one of the essential enzymes of HCV along with NS3 serine protease and NS5B RdRp for processing HCV proteins and replication of HCV. Thus, the inhibition of helicase activities is an important strategy for treating HCV infections. [8] However, discovery of helicase inhibitors has been much slower compared to that of other HCV drug targets.To date, only a few classes of NS3 helicase inhibitors have been reported, partly because high-throughput screens have yielded only a few successful hits. [8a,c] For example, the compounds discovered in the NIH screen based on the molecular-beacon-based helicase assay (MBHA) showed poor activity in cells and turned out to interfere with the assay, [9a] even though another MBHA screening identified compounds that inhibited RNA replication in cells. [9b] Therefore, there is an urgent need for new assays to measure helicase activity that are suitable for high-throughput screens.Herein, we developed a multiplexed helicase assay based on graphene oxide (GO) for high-throughput screening of inhibitors of HCV NS3 helicase and severe acute respiratory syndrome coronavirus (SARS CoV) helicase. Previously, we reported a GO-based helicase assay (GOHA), whi...

Aminoglycosides bind to the influenza A virus promoter (vRNA) at submicromolar concentration. The complex structure between the vRNA and neomycin illustrates that binding of neomycin causes a conformational change which would affect further transcription processes. Thus, aminoglycosides represent lead compounds for the discovery of antiviral therapeutics against influenza A virus.

No abstract