The Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) pandemic represents a global challenge. SARS-CoV-2's ability to replicate in host cells relies on the action of its non-structural proteins, like its main protease (M pro). This cysteine protease acts by processing the viruses' precursor polyproteins. As proteases, together with polymerases, are main targets of antiviral drug design, we here have performed biochemical high throughput screening (HTS) with recombinantly expressed SARS-CoV-2 M pro. A fluorescent assay was used to identify inhibitors in a compound library containing known drugs, bioactive molecules and natural products. These screens led to the identification of 13 inhibitors with IC 50 values ranging from 0.2 μM to 23 μM. The screens confirmed several known SARS-CoV M pro inhibitors as inhibitors of SARS-CoV-2 M pro , such as the organo-mercuric compounds thimerosal and phenylmercuric acetate. Benzophenone derivatives could also be identified among the most potent screening hits. Additionally, Evans blue, a sulfonic acid-containing dye, could be identified as an M pro inhibitor. The obtained compounds could be of interest as lead compounds for the development of future SARS-CoV-2 drugs.

As the Zika virus protease is an essential and well-established target for the development of antiviral agents, we biochemically screened for inhibitors using a purified recombinantly expressed form of this enzyme. As a result, we were able to identify 10 new Zika virus protease inhibitors. These compounds are natural products and showed strong inhibition in the biochemical assays. Inhibitory constants values for the compounds ranged from 5 nM to 8 μM. Among the most potent inhibitors are flavonoids like irigenol hexa-acetate (K i = 0.28 μM), katacine (K i = 0.26 μM), theaflavin gallate (K i = 0.40 μM) and hematein (K i = 0.33 μM). Inhibitors from other groups of natural products include sennoside A (K i = 0.19 μM) and gossypol (K i = 0.70 μM). Several of the obtained compounds are known for their beneficial health effects and have acceptable pharmacokinetic characteristics. Thus, they could be of interest as lead compounds for the development of important and essential Zika antiviral drugs.

No abstract

No abstract

The elucidation of mechanisms behind the thermostability of proteins is extremely important both from the theoretical and applied perspective. Here we report the crystal structure of methylenetetrahydrofolate dehydrogenase (MTHFD) from Thermus thermophilus HB8, a thermophilic model organism. Molecular dynamics trajectory analysis of this protein at different temperatures (303 K, 333 K and 363 K) was compared with homologous proteins from the less temperature resistant organism Thermoplasma acidophilum and the mesophilic organism Acinetobacter baumannii using several data reduction techniques like principal component analysis (PCA), residue interaction network (RIN) analysis and rotamer analysis. These methods enabled the determination of important residues for the thermostability of this enzyme. The description of rotamer distributions by Gini coefficients and Kullback-Leibler (KL) divergence both revealed significant correlations with temperature. The emerging view seems to indicate that a static salt bridge/charged residue network plays a fundamental role in the temperature resistance of Thermus thermophilus MTHFD by enhancing both electrostatic interactions and entropic energy dispersion. Furthermore, this analysis uncovered a relationship between residue mutations and evolutionary pressure acting on thermophilic organisms and thus could be of use for the design of future thermostable enzymes.