Non-Toxic Dimeric Peptides Derived from the Bothropstoxin-I Are Potent SARS-CoV-2 and Papain-like Protease Inhibitors.

The COVID-19 outbreak has rapidly spread on a global scale, affecting the economy and public health systems throughout the world. In recent years, peptide-based therapeutics have been widely studied and developed to treat infectious diseases, including viral infections. Herein, the antiviral effects of the lysine linked dimer des-Cys11, Lys12,Lys13-(pBthTX-I)2K ((pBthTX-I)2K)) and derivatives against SARS-CoV-2 are reported. The lead peptide (pBthTX-I)2K and derivatives showed attractive inhibitory activities against SARS-CoV-2 (EC50 = 28-65 µM) and mostly low cytotoxic effect (CC50 > 100 µM). To shed light on the mechanism of action underlying the peptides' antiviral activity, the Main Protease (Mpro) and Papain-Like protease (PLpro) inhibitory activities of the peptides were assessed. The synthetic peptides showed PLpro inhibition potencies (IC50s = 1.0-3.5 µM) and binding affinities (Kd = 0.9-7 µM) at the low micromolar range but poor inhibitory activity against Mpro (IC50 > 10 µM). The modeled binding mode of a representative peptide of the series indicated that the compound blocked the entry of the PLpro substrate toward the protease catalytic cleft. Our findings indicated that non-toxic dimeric peptides derived from the Bothropstoxin-I have attractive cellular and enzymatic inhibitory activities, thereby suggesting that they are promising prototypes for the discovery and development of new drugs against SARS-CoV-2 infection.

Low-resolution envelope, biophysical analysis and biochemical characterization of a short-chain specific and halotolerant carboxylesterase from Bacillus licheniformis.

Esterases are widely applied in industrial processes due to their versatility, regio- and enantioselectivity, lack of cofactors and stability in organic solvents. Bacillus licheniformis, a microorganism frequently used in industrial and biotechnological applications such as dairy, baking, beverage, pulp and paper, detergent and cosmetics production, organic synthesis and waste management, is a promising source of esterases. Here we describe the biochemical and biophysical characterization of B. licheniformis carboxylesterase BlEst1 and its SAXS-derived molecular envelope. BlEst1 has optimal hydrolytic activity against p­nitrophenyl acetate at pH 7.0 and 40 °C. Furthermore, BlEst1 is stable in different organic solvents such as methanol, isopropanol and butanol. The BlEst1 homology model reveals a typical α/ß hydrolase core with an adjacent auxiliary domain, snuggly fitting the experimental low-resolution SAXS molecular envelope. Moreover, BlEst1 maintained considerable part of its activity in the presence of up to 5 M NaCl and its thermal stability was significantly enhanced by the presence of salt, revealing its halotolerant character. The ability to work under harsh conditions makes BlEst1 an interesting candidate for industrial applications.

Evidence of Adaptive Evolution and Relaxed Constraints in Sex-Biased Genes of South American and West Indies Fruit Flies (Diptera: Tephritidae).

Several studies have demonstrated that genes differentially expressed between sexes (sex-biased genes) tend to evolve faster than unbiased genes, particularly in males. The reason for this accelerated evolution is not clear, but several explanations have involved adaptive and nonadaptive mechanisms. Furthermore, the differences of sex-biased expression patterns of closely related species are also little explored out of Drosophila. To address the evolutionary processes involved with sex-biased expression in species with incipient differentiation, we analyzed male and female transcriptomes of Anastrepha fraterculus and Anastrepha obliqua, a pair of species that have diverged recently, likely in the presence of gene flow. Using these data, we inferred differentiation indexes and evolutionary rates and tested for signals of selection in thousands of genes expressed in head and reproductive transcriptomes from both species. Our results indicate that sex-biased and reproductive-biased genes evolve faster than unbiased genes in both species, which is due to both adaptive pressure and relaxed constraints. Furthermore, among male-biased genes evolving under positive selection, we identified some related to sexual functions such as courtship behavior and fertility. These findings suggest that sex-biased genes may have played important roles in the establishment of reproductive isolation between these species, due to a combination of selection and drift, and unveil a plethora of genetic markers useful for more studies in these species and their differentiation.