The spread of COVID-19 caused by the SARS-CoV-2 outbreak has been growing since its first identification in December 2019. The publishing of the first SARS-CoV-2 genome made a valuable source of data to study the details about its phylogeny, evolution, and interaction with the host. Protein-protein binding assays have confirmed that Angiotensin-converting enzyme 2 (ACE2) is more likely to be the cell receptor through which the virus invades the host cell. In the present work, we provide an insight into the interaction of the viral spike Receptor Binding Domain (RBD) from different coronavirus isolates with host ACE2 protein. By calculating the binding energy score between RBD and ACE2, we highlighted the putative jump in the affinity from a progenitor form of SARS-CoV-2 to the current virus responsible for COVID-19 outbreak. Our result was consistent with previously reported phylogenetic analysis and corroborates the opinion that the interface segment of the spike protein RBD might be acquired by SARS-CoV-2 via a complex evolutionary process rather than a progressive accumulation of mutations. We also highlighted the relevance of Q493 and P499 amino acid residues of SARS-CoV-2 RBD for binding to human ACE2 and maintaining the stability of the interface. Moreover, we show from the structural analysis that it is unlikely for the interface residues to be the result of genetic engineering. Finally, we studied the impact of eight different variants located at the interaction surface of ACE2, on the complex formation with SARS-CoV-2 RBD. We found that none of them is likely to disrupt the interaction with the viral RBD of SARS-CoV-2.
AbstractThe spread of COVID-19 caused by the SARS-CoV-2 outbreak has been growing since its first identification in December 2019. The publishing of the first SARS-CoV-2 genome made a valuable source of data to study the details about its phylogeny, evolution, and interaction with the host. Protein-protein binding assays have confirmed that Angiotensin-converting enzyme 2 (ACE2) is more likely to be the cell receptor through which the virus invades the host cell. In the present work, we provide an insight into the interaction of the viral spike Receptor Binding Domain (RBD) from different coronavirus isolates with host ACE2 protein. By calculating the binding energy score between RBD and ACE2, we highlighted the putative jump in the affinity from a progenitor form of SARS-CoV-2 to the current virus responsible for COVID-19 outbreak. Our result was consistent with previously reported phylogenetic analysis and corroborates the opinion that the interface segment of the spike protein RBD might be acquired by SARS-CoV-2 via a complex evolutionary process rather than a progressive accumulation of mutations. We also highlighted the relevance of Q493 and P499 amino acid residues of SARS-CoV-2 RBD for binding to human ACE2 and maintaining the stability of the interface. Moreover, we show from the structural analysis that it is unlikely for the interface residues to be the result of genetic engineering. Finally, we studied the impact of eight different variants located at the interaction surface of ACE2, on the complex formation with SARS-CoV-2 RBD. We found that none of them is likely to disrupt the interaction with the viral RBD of SARS-CoV-2.
Resistance to 5-Fluorouracil chemotherapy is a major cause of therapeutic failure in colon cancer cure. Development of combined therapies constitutes an effective strategy to inhibit cancer cells and prevent the emergence of drug resistance. For this purpose, we investigated the anti-tumoral effect of thirteen phenolic compounds, from the Tunisian quince Cydonia oblonga Miller, alone or combined to 5-FU, on the human 5-FU-resistant LS174-R colon cancer cells in comparison to parental cells. Our results showed that only Kaempferol was able to chemo-sensitize 5-FU-resistant LS174-R cells. This phenolic compound combined with 5-FU exerted synergistic inhibitory effect on cell viability. This combination enhanced the apoptosis and induced cell cycle arrest of both chemo-resistant and sensitive cells through impacting the expression levels of different cellular effectors. Kaempferol also blocked the production of reactive oxygen species (ROS) and modulated the expression of JAK/STAT3, MAPK, PI3K/AKT and NF-κB. In silico docking analysis suggested that the potent anti-tumoral effect of Kaempferol, compared to its two analogs (Kaempferol 3-O-glucoside and Kampferol 3-O-rutinoside), can be explained by the absence of glucosyl groups. Overall, our data propose Kaempferol as a potential chemotherapeutic agent to be used alone or in combination with 5-FU to overcome colon cancer drug resistance.
Early secreted antigenic target 6 kDa (ESAT‐6) and culture filtrate protein 10 kDa (CFP‐10) are complex proteins secreted by Mycobacterium tuberculosis that play a major role in the pathogenesis of tuberculosis. However, studies focusing on the biological functions of ESAT‐6 led to discordant results and the role of ESAT‐6 remains controversial. In the present study, we aim to address a potential explanation for this discrepancy and to highlight the physiological impact of two conformational states of ESAT‐6. Analysis of a recombinant form of ESAT‐6 by native gel electrophoresis, size exclusion chromatography and CD spectroscopy revealed that ESAT‐6 forms dimers/multimers with higher molecular weight, which disappeared under the action of the detergent amidosulfobetaine‐14 (ASB), giving rise to another conformational state of the protein. NMR has further indicated that ASB‐treated versus nontreated ESAT‐6 adopted distinct structural forms but with no well defined tertiary structure. However, protein–protein docking analysis favored a dimeric state of ESAT‐6. Interestingly, the two preparations presented opposing effects on mycobacterial infectivity, as well as macrophage survival, interferon‐γ secretion and membrane pore formation. Thereafter, we generated a recombinant form of the physiological heterodimer ESAT‐6/CFP‐10 that ASB was also able to dissociate and which showed functions similar to those of ESAT‐6 dimers/multimers. Our data suggest that, in the absence of CFP‐10, the hydrophobic regions of the ESAT‐6 can form dimers/multimers, mimicking the ESAT‐6/CFP‐10 heterodimer, whereas their dissociation generates a protein presenting entirely different activities. Overall, the present study clarifies the intriguing divergences between reports that could be attributed to the ESAT‐6 oligomeric state and sheds light on its importance for a better comprehension of the physiopathology of tuberculosis.
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