Disulfide bond-forming (Dsb) protein is a bacterial periplasmic protein that is essential for the correct folding and disulfide bond formation of secreted or cell wallassociated proteins. DsbA introduces disulfide bonds into folding proteins, and is re-oxidized through interaction with its redox partner DsbB. Mycobacterium tuberculosis, a Gram-positive bacterium, expresses a DsbA-like protein ( Rv2969c), an extracellular protein that has its Nterminus anchored in the cell membrane. Since Rv2969c is an essential gene, crucial for disulfide bond formation, research of DsbA may provide a target of a new class of anti-bacterial drugs for treatment of M.tuberculosis infection. In the present work, the crystal structures of the extracellular region of Rv2969c (Mtb DsbA) were determined in both its reduced and oxidized states. The overall structure of Mtb DsbA can be divided into two domains: a classical thioredoxin-like domain with a typical CXXC active site, and an α-helical domain. It largely resembles its Escherichia coli homologue EcDsbA, however, it possesses a truncated binding groove; in addition, its active site is surrounded by an acidic, rather than hydrophobic surface. In our oxidoreductase activity assay, Mtb DsbA exhibited a different substrate specificity when compared to EcDsbA. Moreover, structural analysis revealed a second disulfide bond in Mtb DsbA, which is rare in the previously reported DsbA structures, and is assumed to contribute to the overall stability of Mtb DsbA. To investigate the disulphide formation pathway in M.tuberculosis, we modeled Mtb Vitamin K epoxide reductase (Mtb VKOR), a binding partner of Mtb DsbA, to Mtb DsbA.
Amino Acid Sequence ; Bacterial Proteins ; chemistry ; metabolism ; Catalytic Domain ; Crystallography, X-Ray ; Disulfides ; chemistry ; Escherichia coli ; metabolism ; Escherichia coli Proteins ; chemistry ; metabolism ; Molecular Docking Simulation ; Molecular Sequence Data ; Mycobacterium tuberculosis ; metabolism ; Oxidation-Reduction ; Protein Disulfide-Isomerases ; chemistry ; metabolism ; Protein Folding ; Protein Structure, Tertiary ; Sequence Alignment ; Static Electricity

Ebolavirus can cause hemorrhagic fever in humans with a mortality rate of 50%-90%. Currently, no approved vaccines and antiviral therapies are available. Human TIM1 is considered as an attachment factor for EBOV, enhancing viral infection through interaction with PS located on the viral envelope. However, reasons underlying the preferable usage of hTIM-1, but not other PS binding receptors by filovirus, remain unknown. We firstly demonstrated a direct interaction between hTIM-1 and EBOV GP in vitro and determined the crystal structures of the Ig V domains of hTIM-1 and hTIM-4. The binding region in hTIM-1 to EBOV GP was mapped by chimeras and mutation assays, which were designed based on structural analysis. Pseudovirion infection assays performed using hTIM-1 and its homologs as well as point mutants verified the location of the GP binding site and the importance of EBOV GP-hTIM-1 interaction in EBOV cellular entry.
Ebolavirus ; metabolism ; Flow Cytometry ; Glycoproteins ; metabolism ; Hepatitis A Virus Cellular Receptor 1 ; Hepatitis A Virus Cellular Receptor 2 ; Humans ; Membrane Glycoproteins ; metabolism ; Membrane Proteins ; metabolism ; Protein Binding ; Receptors, Virus ; metabolism ; Surface Plasmon Resonance ; Viral Envelope Proteins ; metabolism ; Viral Proteins ; metabolism

Coxsackievirus A16 belongs to the family Picornaviridae, and is a major agent of hand-foot-and-mouth disease that infects mostly children, and to date no vaccines or antiviral therapies are available. 2A protease of enterovirus is a nonstructural protein and possesses both self-cleavage activity and the ability to cleave the eukaryotic translation initiation factor 4G. Here we present the crystal structure of coxsackievirus A16 2A protease, which interestingly forms hexamers in crystal as well as in solution. This structure shows an open conformation, with its active site accessible, ready for substrate binding and cleavage activity. In conjunction with a previously reported "closed" state structure of human rhinovirus 2, we were able to develop a detailed hypothesis for the conformational conversion triggered by two "switcher" residues Glu88 and Tyr89 located within the bll2-cII loop. Substrate recognition assays revealed that amino acid residues P1', P2 and P4 are essential for substrate specificity, which was verified by our substrate binding model. In addition, we compared the in vitro cleavage efficiency of 2A proteases from coxsackievirus A16 and enterovirus 71 upon the same substrates by fluorescence resonance energy transfer (FRET), and observed higher protease activity of enterovirus 71 compared to that of coxsackievirus A16. In conclusion, our study shows an open conformation of coxsackievirus A16 2A protease and the underlying mechanisms for conformational conversion and substrate specificity. These new insights should facilitate the future rational design of efficient 2A protease inhibitors.
Coxsackievirus Infections ; virology ; Crystallography, X-Ray ; Cysteine Endopeptidases ; chemistry ; genetics ; Fluorescence Resonance Energy Transfer ; Hand, Foot and Mouth Disease ; enzymology ; pathology ; virology ; Humans ; Picornaviridae ; chemistry ; enzymology ; genetics ; Protein Conformation ; Structure-Activity Relationship ; Substrate Specificity ; Viral Proteins ; chemistry ; genetics

Objective : To identify the main components in the extracts of different parts of Juandan Baihe (Lilium lancifolium) by ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) technology and investigate their hypoglycemic activities. Methods: The MS fragmentation pathways of the main types of compounds in Juandan Baihe (Lilium lancifolium) were studied, and the main components in the extracts were systematically identified using MS fragmentation pathways combined with MS mining technology. Based on the hyperglycemia male mouse model [specific pathogen free (SPF)-grade Kunming mice] induced by streptozotocin (intragastric administration of 80 mg/kg for 3 d), the hypoglycemic effects of extracts of Juandan Baihe (Lilium lancifolium) roots, stems, corms, leaves, and flowers were evaluated by measuring the changes of blood glucose, daily water consumption, daily food intake, and body weight. Result: The MS fragmentation pathways of regalosides, dioscins, phenylpropanoids, flavonoids, and chlorogenic acids in Juandan Baihe (Lilium lancifolium) were clarified, and a mining method for compounds in this plant was constructed. A total of 58 compounds, including 6 chlorogenic acids, 14 regalosides, 13 phenylpropanoids, 5 flavonoids, and 20 dioscins, were identified from the roots, stems, corms, leaves, and flowers of Juandan Baihe (Lilium lancifolium). Among them, 30 compounds were reported for the first time from this plant. The root and corm extracts demonstrated significant hypoglycemic activities by reducing blood glucose levels from 23.76 ± 1.21 and 24.29 ± 1.35 mmol/L to 17.21 ± 1.23 and 18.78 ± 1.49 mmol/L, respectively (P < 0.05). The roots and corms extracts could also attenuate the symptoms of polydipsia (P < 0.01), polyphagia (P < 0.05), and weight loss caused by diabetes. Conclusion This study clarifies that the roots of Juandan Baihe (Lilium lancifolium) are rich in regalosides and dioscins for the first time, and have significant hypoglycemic activities, providing the foundation for the comprehensive utilization of this plant and the development of hypoglycemic drugs.

Unlike the well-established picture for the entry of enveloped viruses, the mechanism of cellular entry of non-enveloped eukaryotic viruses remains largely mysterious. Picornaviruses are representative models for such viruses, and initiate this entry process by their functional receptors. Here we present the structural and functional studies of SCARB2, a functional receptor of the important human enterovirus 71 (EV71). SCARB2 is responsible for attachment as well as uncoating of EV71. Differences in the structures of SCARB2 under neutral and acidic conditions reveal that SCARB2 undergoes a pivotal pH-dependent conformational change which opens a lipid-transfer tunnel to mediate the expulsion of a hydrophobic pocket factor from the virion, a pre-requisite for uncoating. We have also identified the key residues essential for attachment to SCARB2, identifying the canyon region of EV71 as mediating the receptor interaction. Together these results provide a clear understanding of cellular attachment and initiation of uncoating for enteroviruses.
Acids ; chemistry ; Amino Acid Sequence ; Animals ; Capsid Proteins ; chemistry ; genetics ; metabolism ; Enterovirus A, Human ; genetics ; metabolism ; physiology ; HEK293 Cells ; Host-Pathogen Interactions ; Humans ; Hydrogen-Ion Concentration ; Lysosome-Associated Membrane Glycoproteins ; chemistry ; genetics ; metabolism ; Molecular Docking Simulation ; Molecular Sequence Data ; Protein Binding ; Protein Conformation ; Protein Interaction Mapping ; Protein Structure, Tertiary ; RNA, Viral ; genetics ; metabolism ; Receptors, Scavenger ; chemistry ; genetics ; metabolism ; Sequence Homology, Amino Acid ; Sf9 Cells ; Static Electricity ; Virion ; genetics ; metabolism ; Virus Attachment

Objective:To establish a rapid method for detecting the activity of 2019-nCoV2.Methods:The reverse transcription-quantitative polymerase chain reaction (RT-qPCR) detection system was screened after propidium monoazide (PMA) treatment and exposure to heat-inactivated 2019-nCoV samples, and the PMA pretreatment conditions were optimized to establish the 2019-nCoV PMA-RT-qPCR detection method . The established method was used to detect virus inactivated by different temperatures and chlorine-containing disinfectant, to evaluate its effect in detecting virus activity.Results:For the PMA-RT-qPCR assay, 200 μmol/L of PMA, 10 min of incubation time, 15 min of exposure time, and the CDC ORF1ab detection system were selected; there was no significant difference in the result of PMA-RT-qPCR and direct RT-qPCR for the active virus; the Ct values of PMA-RT-qPCR for virus inactivated by 95 ℃ and chlorine-containing disinfectant were higher than that of control groups at different dilutions; only partial dilutions of 70 ℃ and 56 ℃ heat-inactivated virus had higher Ct values than control groups. Conclusions:The established PMA-RT-qPCR for 2019-nCoV activity detection method has a good detection effect on the virus inactivated by 95 ℃ heat and chlorine disinfectant, and provides an auxiliary means for judging the infectivity of the virus in the sample.

Objective To briefly retrospect the production and quality control of 64 Cu(n = 9) in Department of Nuclear Medicine of Peking University Cancer Hospital in order to provide useful information for the further production and application of this novel radionuclide. Methods 64 Ni(p, n) 64 Cu nuclide re-action was used for the 64 Cu production. Firstly, a new electro-planting device for 64 Ni planting was de-signed. HM-20 cyclotron was applied to irradiate the slice for 5-8 h. 64 CuCl2 was purified, collected and in-jected into normal mice. MicroPET was conducted to monitor the metabolism in vivo. Results A new type of electro-planting device was designed and assembled. The enriched 64 Ni target showed smooth, even, dense surface and without obvious pits and cracks. High specific 64 Cu (1.3-4.1 GBq) can be collected after radio-chemical purification. 64 Cu was finally dissolved in 0.01 mol/ L HCl with high radionuclide purity (over 99.97％). MicroPET of 64 CuCl2 in normal mice showed that the radioactivity was mainly accumulated in the liver. Conclusion A new and real-time observable device for 64 Ni electro-plating has been designed and successfully used in the production of 64 Cu with high specific activity.

Objective:To evaluate the clinical effect of high-intensity focused ultrasound(HIFU)and drug con-servative treatment on the treatment of type Ⅰ and type Ⅱ cesarean scar pregnancy(CSP).Methods:A retrospec-tive analysis was performed on 191 patients diagnosed with type Ⅰ and type Ⅱ CSP by ultrasonography and trea-ted in Mianyang Central Hospital from January 2018 to December 2021,and they were divided into drug group(n=67)and HIFU group(n=124)according to different treatment methods before curettage surgery.After receiv-ing conservative drug treatment or HIFU treatment,preformnegative pressure suction curettage under ultrasound monitoring to evaluate the effectiveness and safety of the two pretreatment methods.Results:There were no sig-nificant differences in age,number of cesarean sections,gestational age,the maximum diameter of the gestational sac,number of incision pregnancies,the β-hCG level before pretreatment,the heart tube pulse in the gestational sac,size of fetal bud,and fertility requirements between the medication group and HIFU group(P＞0.05).The proportion of type Ⅱ incision in HIFU group was higher than that in drug group(P＜Q.05).There were no signifi-cant differences between the two groups in intraoperative bleeding,treatment outcome effective rate after pretreat-ment,postoperative vaginal bleeding duration,postoperative uterine cavity residual,rate of reoperation and rate of repregnancy(P＞0.05).There were statistical differences between the two groups in the operation time of curet-tage surgery,whether the operation method was changed after pre-treatment,total hospital stay,β-hCG recovery time and hospitalization cost(P＜0.05).Following up to November 2022,there were 12 cases re-pregnancies in the drug group and 16 cases re-pregnancies in the HIFU group.Conclusions:For type Ⅰ and type Ⅱ CSP,HIFU pretreatment before negative pressure suction curettage under ultrasound monitoring is a safe and effective treat-ment,which improves the treatment effect and reduces the hospitalization time of patients.It may be an effective clinical therapy for type Ⅰ and type Ⅱ CSP treatment.

Seven novel linear polyketides,talaketides A-G(1-7),were isolated from the rice media cultures of the mangrove sed-iment-derived fungus Talaromyces sp.SCSIO 41027.Among these,talaketides A-E(1-5)represented unprecedented unsaturated lin-ear polyketides with an epoxy ring structure.The structures,including absolute configurations of these compounds,were elucidated through detailed analyses of nuclear magnetic resonance(NMR)and high-resolution mass spectrometry(HR-MS)data,as well as elec-tronic custom distributors(ECD)calculations.In the cytotoxicity screening against prostate cancer cell lines,talaketide E(5)demon-strated a dose-dependent inhibitory effect on prostate cancer PC-3 cell lines,with an IC50 value of 14.44 μmol·L-1.Moreover,com-pound 5 significantly inhibited the cloning formation of PC-3 cell lines and arrested the cell cycle in S-phase,ultimately inducing ap-optosis.These findings indicate that compound 5 may serve as a promising lead compound for the development of a potential treat-ment for prostate cancer.

Entero virus 71 (EV71) causes hand, foot, and mouth disease (HFMD) and occasionally leads to severe neurological complications and even death. Scavenger receptor class B member 2 (SCARB2) is a functional receptor for EV71, that mediates viral attachment, internalization, and uncoating. However, the exact binding site of EV71 on SCARB2 is unknown. In this study, we generated a monoclonal antibody (mAb) that binds to human but not mouse SCARB2. It is named JL2, and it can effectively inhibit EV71 infection of target cells. Using a set of chimeras of human and mouse SCARB2, we identified that the region containing residues 77-113 of human SCARB2 contributes significantly to JL2 binding. The structure of the SCARB2-JL2 complex revealed that JL2 binds to the apical region of SCARB2 involving α-helices 2, 5, and 14. Our results provide new insights into the potential binding sites for EV71 on SCARB2 and the molecular mechanism of EV71 entry.
Amino Acid Sequence ; Animals ; Antibodies, Monoclonal ; chemistry ; genetics ; metabolism ; Binding Sites ; Cell Line ; Crystallography, X-Ray ; Enterovirus A, Human ; drug effects ; genetics ; growth & development ; immunology ; Fibroblasts ; drug effects ; virology ; Gene Expression ; HEK293 Cells ; Humans ; Immunoglobulin Fab Fragments ; chemistry ; genetics ; metabolism ; Lysosome-Associated Membrane Glycoproteins ; chemistry ; genetics ; immunology ; Mice ; Models, Molecular ; Protein Binding ; Protein Conformation, alpha-Helical ; Protein Conformation, beta-Strand ; Protein Interaction Domains and Motifs ; Receptors, Scavenger ; chemistry ; genetics ; immunology ; Receptors, Virus ; chemistry ; genetics ; immunology ; Recombinant Fusion Proteins ; chemistry ; genetics ; immunology ; Sequence Alignment ; Sequence Homology, Amino Acid ; Sf9 Cells ; Spodoptera ; Thermodynamics