Structural analysis of EhPSP in complex with 3-phosphoglyceric acid from Entamoeba histolytica reveals a basis for its lack of phosphoglycerate mutase activity

Identification of Small Molecule Inhibitors Targeting Phosphoserine Phosphatase: A Novel Target for the Development of Antiamoebic Drugs

Amoebiasis, a widespread disease caused by the protozoan parasite Entamoeba histolytica, poses challenges due to the adverse effects of existing antiamoebic drugs and rising drug resistance. Novel targeted drugs are in need of the hour to combat the prevalence of this disease. Given the significance of cysteine for Entamoeba survival, the rate-determining step in the serine (the sole substrate of cysteine synthesis) biosynthetic pathway, i.e., the conversion of 3-phosphoserine to l-serine catalyzed by phosphoserine phosphatase (PSP), emerges as a promising drug target. Our previous study unveils the essential role of EhPSP in amoebas' survival, particularly under oxidative stress, by increasing cysteine production. The study also revealed that EhPSP differs significantly from its human counterpart, both structurally and biochemically, highlighting its potential as a viable target for developing new antiamoebic drugs. In the present study, employing in silico screening of vast natural and synthetic small chemical compound libraries, we identified 21 potential EhPSP inhibitor molecules. Out of the 21 compounds examined, only five could inhibit the catalytic activity of EhPSP. The inhibition capability of these five compounds was subsequently validated by in silico binding free energy calculations, SPR-based real-time binding studies, and molecular simulations to assess the stability of the EhPSP-inhibitor complexes. By identifying the five potential inhibitors that can target cysteine synthesis via EhPSP, our findings establish EhPSP as a drug candidate that can serve as a foundation for antiamoebic drug research.

Deciphering protein-mediated underwater adhesion in an invasive biofouling ascidian: Discovery, validation, and functional mechanism of an interfacial protein

Discovering macromolecules and understanding the associated mechanisms involved in underwater adhesion are essential for both studying the fundamental ecology of benthos in aquatic ecosystems and developing biomimetic adhesive materials in industries. Here, we employed quantitative proteomics to assess protein expression variations during the development of the distinct adhesive structure - stolon in the model fouling ascidian, Ciona robusta. We found 16 adhesive protein candidates with increased expression in the stolon, with ascidian adhesive protein 1 (AAP1) being particularly rich in adhesion-related signal peptides, amino acids, and functional domains. Western blot and immunolocalization analyses confirmed the prominent AAP1 signals in the mantle, tunic, stolon, and adhesive footprints, indicating the interfacial role of this protein. Surface coating and atomic force microscopy experiments verified AAP1's adhesion to diverse materials, likely through the specific electrostatic and hydrophobic amino acid interactions with various substrates. In addition, molecular docking calculations indicated the AAP1's potential for cross-linking via hydrogen bonds and salt bridges among Von Willebrand factor type A domains, enhancing its adhesion capability. Altogether, the newly discovered interfacial protein responsible for permanent underwater adhesion, along with the elucidated adhesion mechanisms, are expected to contribute to the development of biomimetic adhesive materials and anti-fouling strategies. STATEMENT OF SIGNIFICANCE: Discovering macromolecules and studying their associated mechanisms involved in underwater adhesion are essential for understanding the fundamental ecology of benthos in aquatic ecosystems and developing innovative bionic adhesive materials in various industries. Using multidisciplinary analytical methods, we identified an interfacial protein - Ascidian Adhesive Protein 1 (AAP1) from the model marine fouling ascidian, Ciona robusta. The interfacial functions of AAP1 are achieved by electrostatic and hydrophobic interactions, and the Von Willebrand factor type A domain-based cross-linking likely enhances AAP1's interfacial adhesion. The identification and validation of the interfacial functions of AAP1, combined with the elucidation of adhesion mechanisms, present a promising target for the development of biomimetic adhesive materials and the formulation of effective anti-fouling strategies.

Chemical composition and therapeutic mechanism of Xuanbai Chengqi Decoction in the treatment of COVID-19 by network pharmacology, molecular docking and molecular dynamic analysis

Xuanbai Chengqi Decoction (XBCQD), a classic traditional Chinese medicine, has been widely used to treat COVID-19 in China with remarkable curative effect. However, the chemical composition and potential therapeutic mechanism is still unknown. Here, we used multiple open-source databases and literature mining to select compounds and potential targets for XBCQD. The COVID-19 related targets were collected from GeneCards and NCBI gene databases. After identifying putative targets of XBCQD for the treatment of COVID-19, PPI network was constructed by STRING database. The hub targets were extracted by Cytoscape 3.7.2 and MCODE analysis was carried out to extract modules in the PPI network. R 3.6.3 was used for GO enrichment and KEGG pathway analysis. The effective compounds were obtained via network pharmacology and bioinformatics analysis. Drug-likeness analysis and ADMET assessments were performed to select core compounds. Moreover, interactions between core compounds and hub targets were investigated through molecular docking, molecular dynamic (MD) simulations and MM-PBSA calculations. As a result, we collected 638 targets from 61 compounds of XBCQD and 845 COVID-19 related targets, of which 79 were putative targets. Based on the bioinformatics analysis, 10 core compounds and 34 hub targets of XBCQD for the treatment of COVID-19 were successfully screened. The enrichment analysis of GO and KEGG indicated that XBCQD mainly exerted therapeutic effects on COVID-19 by regulating signal pathways related to viral infection and inflammatory response. Meanwhile, the results of molecular docking showed that there was a stable binding between the core compounds and hub targets. Moreover, MD simulations and MM-PBSA analyses revealed that these compounds exhibited stable conformations and interacted well with hub targets during the simulations. In conclusion, our research comprehensively explained the multi-component, multi-target, and multi-pathway intervention mechanism of XBCQD in the treatment of COVID-19, which provided evidence and new insights for further research.