Biomedical subjects

Hong Liu

Publications and source records attributed to Hong Liu.

At least 19 recordsLinked to original sources

PubMed2026

Cerium dioxide nanoparticle exposure attenuates mobility-linked antibiotic resistome signatures across the soil-lettuce continuum.

Antibiotic resistance genes (ARGs) are contaminants of emerging concern in agricultural microbiomes. Their association with mobile genetic elements (MGEs) can enhance dissemination across soil-plant interfaces, creating potential environmental and food-chain exposure risks. However, how engineered nanoparticles modulate relative ARG abundance and mobility-linked resistome features in plant-associated microbiomes remains poorly understood. Here, we examined the effects of graded, experimentally elevated cerium dioxide nanoparticle (CeO2 NP) loadings in a soil-lettuce system by integrating compartment-resolved metagenomics, ARG-MGE co-occurrence analysis, putative host-reservoir profiling, transcriptomics, and functional assays. Metagenomic profiling identified 16 ARG types and 125 subtypes and revealed niche-dependent microbiome restructuring under CeO2 NP exposure. Rhizosphere relative ARG abundance showed a negative dose-associated trend, although overall inter-group differences were not significant, whereas leaf endophytes showed a weaker response. Relative MGE abundance decreased significantly in both compartments, and lower assembly-level ARG-MGE co-occurrence reflected fewer ARGs detected in MGE-associated genomic contexts, whereas fewer multi-ARG contigs suggested reduced ARG clustering and potential co-selection. Putative host-reservoir analysis associated key efflux determinants with bacterial families whose relative representation declined following CeO2 NP exposure. Transcriptomic profiling of representative putative ARG hosts revealed host-specific responses, including downregulation of genes involved in central metabolism and Sec-dependent trafficking. Complementary host assays showed reduced apparent envelope permeability and lower recovery of tetracycline-resistant recipient-identity colonies in the plasmid-associated host system. Together, under the tested elevated-loading conditions, CeO2 NP exposure was associated with lower relative ARG signals and weaker mobility-linked resistome features across the soil-lettuce continuum, providing mechanistic insight into nanoparticle-resistome interactions in soil-plant systems.

ARG dissemination↗

PubMed2026

Efficacy and safety of ferric citrate tablets in Chinese patients with hyperphosphatemia undergoing maintenance hemodialysis: a multicenter, randomized, open-label, active-controlled, phase III trial.

BACKGROUND: This study aimed to evaluate the efficacy and safety of ferric citrate tablets in Chinese patients with hyperphosphatemia undergoing maintenance hemodialysis (MHD). METHODS: In this phase III, multicenter, randomized, open-label, non-inferiority trial, patients with hyperphosphatemia on maintenance hemodialysis were randomly assigned to receive either ferric citrate or sevelamer carbonate tablets for 12 weeks. The primary endpoint was the change in serum phosphorus levels from baseline to week 12, with a non-inferiority margin of 0.32 mmol/L. Secondary endpoints included changes in serum calcium, intact parathyroid hormone, and safety assessments. RESULTS: A total of 239 patients were randomized to the ferric citrate group (n = 119) or the sevelamer carbonate group (n = 120). The mean change in serum phosphorus levels was -0.70 ± 0.50 mmol/L in the ferric citrate group and -0.61 ± 0.59 mmol/L in the sevelamer carbonate group (least squares mean difference, -0.09 mmol/L; 95% CI, -0.24 to 0.05 mmol/L; non-inferiority margin, 0.32 mmol/L). No significant inter-group differences were found in the percentage of patients achieving target phosphorus levels (49.09% vs. 48.28%, p = 0.902). Ferric citrate significantly improved iron-related parameters and hemoglobin levels. Most treatment-emergent adverse events were mild, with gastrointestinal disorders being the most common. CONCLUSIONS: Ferric citrate tablets were non-inferior to sevelamer carbonate in reducing serum phosphorus levels in hyperphosphatemia patients on maintenance hemodialysis, with the added benefit of improving iron-related anemia and a favorable safety profile.

Adult↗

PubMed2026

Insights into the Life Cycle and Therapeutic Agents for Monkeypox Virus Infection.

Since the first confirmed case in 1970, the monkeypox virus (MPXV) has emerged as a significant threat to global public health. The World Health Organization (WHO) has declared it a Public Health Emergency of International Concern (PHEIC) on two occasions. Despite decades of research, only tecovirimat has been approved by the European Medicines Agency (EMA) for the treatment of MPXV infection. The genome and structure are similar between MPXV and other orthopoxviruses (OPXVs), suggesting that the strategies used for other OPXVs may be applicable to MPXV. This review systematically summarizes the genome, structure, and critical stages in the life cycle of OPXVs, especially MPXV. A variety of antiviral agents against MPXV and other OPXVs are discussed according to their distinct mechanisms of action: 1) blocking viral entry and fusion, 2) inhibiting DNA replication and processing, 3) disrupting transcription and mRNA processing, 4) preventing virion assembly, maturation and release, 5) modulating immune responses, and 6) mechanism unknown. Overall, this article provides a systematic review of current research progress on potential therapeutic targets and agent for MPXV, aiming to offer innovative insights and strategies for the development of effective therapeutic agents against mpox.

Animals↗

PubMed2026

In vivo genome editing of central nervous system SIV reservoirs in ART-suppressed rhesus macaques.

Latent human immunodeficiency virus type 1 (HIV-1) reservoirs in the central nervous system (CNS) may sustain viral persistence and neuroinflammation contributing to HIV-associated neurocognitive disorders (HAND) despite suppressive ART. AAV9-delivered CRISPR has successfully edited SIV proviral DNA in peripheral tissues with acceptable safety profiles, but the extent of in vivo genome editing in the brain remains unclear. Using SIV-infected rhesus macaques, we mapped intact proviral DNA across CNS regions and tested systemic AAV9-CRISPR-Cas9 targeting conserved sites within Ψ packaging signal and Gag region. Ten adult rhesus macaques were infected with genetically barcoded SIVmac239, suppressed with ART, then randomized to receive intravenous AAV9-SaCas9 with dual gRNAs (Ψ + Gag) or a Cas9-only control. At necropsy after viral rebound, SIV genomes were detected in multiple brain regions as well as lymphoid tissues, confirming the CNS as a persistent reservoir during ART. Barcode analysis revealed region-specific patterns consistent with compartmentalized CNS persistence. In CRISPR-treated animals, proviral editing was measurable across anatomically distinct CNS sites. These findings demonstrate that intact and potentially replication-competent virus persists in the primate brain under ART and that systemic AAV9-CRISPR can reach and edit proviral DNA in this sanctuary, supporting genome editing as a strategy toward durable remission of CNS reservoirs.

ART↗

PubMed2026

Effect of intraoperative 40-hz gamma-frequency auditory stimulation on postoperative delirium in older adults undergoing major surgery: a randomized clinical trial protocol.

INTRODUCTION: Postoperative delirium (POD) is a common and clinically significant complication among older adults undergoing major surgery under general anesthesia. Gamma-frequency (40-Hz) auditory stimulation has demonstrated potential neuroprotective and cognition-enhancing effects, suggesting a plausible role in perioperative delirium prevention. However, direct clinical evidence supporting intraoperative 40-Hz auditory stimulation in reducing POD remains limited, warranting rigorous evaluation in a randomized trial. PATIENTS AND METHODS: This prospective, parallel-group, randomized controlled trial will enroll 550 older adults scheduled for major noncardiac, nonneurosurgical surgery under general anesthesia. Participants will be randomized in a 1:1 ratio to either the active stimulation group, receiving intraoperative 40-Hz gamma-frequency auditory stimulation delivered via headphones for 2 h following successful anesthesia induction, or the sham stimulation group, wearing headphones without active auditory output. The primary outcome is the incidence of POD on postoperative day 1 though 3, assessed using the Confusion Assessment Method (CAM) or the CAM for the ICU (CAM-ICU). Secondary outcomes include POD severity, sleep quality, pain scores, analgesic consumption, the incidence of postoperative nausea and vomiting (PONV), rescue antiemetic use, duration of post-anesthesia care unit (PACU) stay, length of hospital stay, quality of postoperative recovery, incidence of perioperative adverse events; postoperative morbidity, health-related quality of life, and all-cause 30-day mortality. DISCUSSION: This trial will determine whether intraoperative 40-Hz gamma-frequency auditory stimulation reduces the incidence of POD among older adults undergoing major surgery under general anesthesia. If efficacious, this noninvasive intervention could constitute a feasible perioperative strategy to mitigate delirium risk and enhance postoperative recovery. CLINICAL TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2500115156).

Humans↗

PubMed2026

Molecular mechanisms of plant thermal response: from signal transduction and epigenetic regulation to signaling integration.

Global warming intensification elevates heat stress to one of the major threats to crop productivity. This review synthesizes recent advances in understanding the mechanisms governing plant responses to both moderate and acute heat stress, with a focus on the integration of epigenetic regulation and signaling networks that underpin thermal adaptation. This review highlights how transcription factors PHYTOCHROME-INTERACTING FACTOR 4 (PIF4, during thermomorphogenesis) and HEAT SHOCK FACTOR A1s (HSFA1s, in heat shock responses) orchestrate plant adaptive growth through crosstalk among light, circadian, and hormone signaling pathways. Importantly, epigenetic mechanisms, including histone variant H2A.Z dynamics and histone modification reprogramming, function as central regulators of thermal plasticity. Key among these processes are HSFA2-mediated chromatin remodeling and small interfering RNA (siRNA)-dependent control of transgenerational thermomemory. Despite this progress, fundamental questions persist regarding temperature sensing, HSFA1s activation dynamics, and stress signal integration. Multi-omics and synthetic biology approaches are proposed to be pivotal in deciphering conserved principles of plant thermal resilience, ultimately providing a theoretical foundation and molecular breeding strategies for climate-smart crops.

Epigenesis, Genetic↗

PubMed2025

Evolutionary legacy of the "living fossil" genus Parrotia (Hamamelidaceae): genomic insights into species divergence and polygenic adaptation.

Despite their long evolutionary history, the genomic basis of adaptation and speciation in "living fossil" plants remain largely unexplored. Parrotia, a Tertiary relict tree genus with two extant species, P. subaequalis and P. persica, exhibits a disjunct distribution between East Asia and West Asia. Here, we present the first chromosome-level assemblies for both species, confirmed their sibling relationship, and dated the speciation event to the early Miocene. The recent proliferation of long-terminal repeat retrotransposons has driven the genome expansion in P. subaequalis. We detected widespread heterogeneous genomic differentiation between species. Extensive signals of divergent selection, local adaptation, and elevated Ka/Ks ratios in Parrotia indicate that this genus has undergone adaptive evolution in distinct refugia, challenging the notion of it as an "evolutionary dead end". Our findings provide new insights into the genomic evolution, environmental adaptation, and speciation of this "living fossil" tree genus.

Genome, Plant↗

PubMed2007

Discovering potassium channel blockers from synthetic compound database by using structure-based virtual screening in conjunction with electrophysiological assay.

Potassium ion (K+) channels are attractive targets for drug discovery because of the essential roles played in biological systems. However, high-throughput screening (HTS) cannot be used to screen K+ channel blockers. To overcome this disadvantage of HTS, we have developed a virtual screening approach for discovering novel blockers of K+ channels. On the basis of a three-dimensional model of the eukaryotic K+ channels, molecular docking-based virtual screening was employed to search the chemical database MDL Available Chemicals Directory (ACD). Compounds were ranked according to their relative binding energy, favorable shape complementarity, and potential to form hydrogen bonds with the outer mouth of the K+ channel model. Twenty candidate compounds selected from the virtual screening were examined using the whole-cell voltage-clamp recording in rat dissociated hippocampal neurons. Among them, six compounds (5, 6, 8, 18-20) potently blocked both the delayed rectifier (IK) and fast transient K+ currents (IA). When applied externally, these six compounds preferentially blocked IK with potencies 2- to 500-fold higher than that of tetraethylammonium chloride. Intracellular application of the six compounds had no effect on both K+ currents. In addition, the interaction models and binding free energy calculations demonstrated that hydrophobic interaction and solvent effects play important roles in the inhibitory activities of these compounds. The results demonstrated that structure-based computer screening strategy could be used to identify novel, structurally diverse compounds targeting the pore binding pocket of the outer mouth of voltage-gated K+ channels. This study provides an alternative way of finding new blockers of voltage-gated K+ channels, while the techniques for high-throughput screening of K+ channel drugs remain in development.

Animals↗

PubMed2007

Design, synthesis, antitumor evaluations and molecular modeling studies of novel 3,5-substituted indolin-2-one derivatives.

AIM: To design and synthesize a novel class of antitumor agents, featuring the 3, 5-substituted indolin-2-one framework. METHODS: Based on enzyme binding features of (Z)-SU5402, introducing a beta-pyrrole group at the 3-position of the indolin- 2-one core, a series of novel 3,5-substituted indolin-2-ones were designed and synthesized. Four human carcinoma cell lines of A-431, A-549, MDA-MB-468, and Autosomal Dominant Polycystic Kidney disease were chosen for the cell proliferation assay. RESULTS: Twenty new compounds (1a-t) with E configuration have been designed, synthesized and bioassayed. Their structural features were determined by nuclear magnetic resonance (NMR) spectra, low- and high-resolution mass spectra, and confirmed by X-ray crystallography. Although the enzyme assay showed a weak inhibition effect against the epidermal growth factor receptor, vascular endothelial growth factor receptor, fibroblast growth factor receptor and platelet-derived growth factor receptor tyrosine kinases, the cell-based antitumor activity was promising. Compounds 1 g and 1 h showed higher inhibitory activity toward the A-549 and MDA-MB-468 cell lines with IC(50 ) of 0.065-9.4 micromol/L. CONCLUSION: This study provides a new template for further development of potent antitumor drugs.

Antineoplastic Agents↗

PubMed2007

Role for HER2/neu and HER3 in fulvestrant-resistant breast cancer.

Tamoxifen resistance is common for estrogen receptor alpha (ERalpha) positive breast cancer. Second-line therapies include aromatase inhibitors or fulvestrant. We have shown previously that fulvestrant reversed 17beta-estradiol-induced tumor regression of tamoxifen-stimulated MCF-7 xenografts (MCF-7TAMLT) treated for >5 years with tamoxifen in athymic mice and paradoxically stimulated growth. We investigated mechanisms responsible for growth by fulvestrant in the presence of physiologic estradiol and therapeutic strategies in vivo. The results demonstrated that only estradiol increased expression of the estrogen-responsive genes, c-myc, igf-1, cathepsin D, and pS2 mRNAs, in MCF-7E2 and MCF-7TAMLT tumors. Tamoxifen or fulvestrant decreased the estradiol-induced increase of these mRNAs in both tumor models. However, tyrosine-phosphorylated HER2/ neu, HER3, phospho-extracellular-regulated kinase-1/2 (ERK-1/2), and phospho-glycogen synthetase kinase 3alpha (GSK3alpha) and beta proteins were increased in MCF-7TAMLT tumors treated with fulvestrant compared to estradiol, control, or tamoxifen. Phospho-HER2/neu interacted with HER3 protein in MCF-7TAMLT tumors. In order to determine whether the functional interaction of HER2/neu with HER3 is critical for growth of fulvestrant-stimulated MCF-7TAMLT tumors, pertuzumab (an antibody that blocks HER2/neu-HER3 interaction) was used in an in vivo xenograft growth assay. Only growth of fulvestrant-treated MCF-7TAMLT xenografts was decreased significantly by 37.2% in response to pertuzumab (P=0.004). Pertuzumab specifically decreased the interaction of HER2/neu protein with HER3 in fulvestrant-stimulated MCF-7TAMLT tumors. These results suggested growth of MCF-7TAMLT tumors by tamoxifen or fulvestrant is potentially independent of ERalpha transcriptional activity as evidenced by lack of induction of four estrogen-responsive genes. The results suggested that growth of MCF-7TAMLT tumors treated with fulvestrant in the presence of physiologic estradiol is in part mediated through enhanced signaling from the HER2/neu-HER3 pathway as pertuzumab partially inhibited growth and the interaction of HER2/neu with HER3 in vivo.

Animals↗

PubMed2006

Adaptation of salt-tolerant Myxococcus strains and their motility systems to the ocean conditions.

More and more studies have indicated that myxobacteria are able to live in seawater conditions, which, however, can decrease the fruiting body formation ability and also the adventurous (A) and social (S) motility systems of the myxobacteria. To learn the adaptation mechanism of the salt-tolerant myxobacteria to marine conditions, we analyzed 10 salt-tolerant Myxococcus strains of their fruiting body formation and motility. The isolates were from marine samples and possessed different levels of salt tolerance. They had the dual motility system and formed fruiting bodies in the presence of suitable seawater concentrations. Some high salt-tolerant strains even lost their fruiting abilities in the absence of seawater. In response to the presence of seawater, the S-motility was found to be increased in the high salt-tolerants but decreased in the low salt-tolerants. The A-motility, on the other hand, was observed in all the salt-tolerant Myxococcus strains, but increased or decreased in response to the presence of seawater. Perceived shifts of fruiting body formation abilities and motilities discovered in the salt-tolerant Myxococcus strains suggested an ecological adaptation of myxobacterial social behaviors to the marine environments.

Adaptation, Physiological↗

PubMed2006

Bicyclic carbamates as inhibitors of papain-like cathepsin proteases.

A 6-oxa-1-aza-bicyclo[3.2.1]octan-7-one system inhibits the proteolytic activity of several cysteine proteases belonging to the papain family. In vitro mechanistic studies and in silico calculations suggest that the minimal pi-overlap between the bridgehead nitrogen and the carbonyl leads to a considerable weakening of the urethane system, making it susceptible to nucleophilic attack from the active site thiol group. The resulting covalent adduct is slowly hydrolyzed, releasing the hydroxypiperidine product of the inhibitor. Synthesis and testing of a set of analogs led to variable protease subtype selectivities ranging from micromolar to nanomolar potencies.

Binding Sites↗

PubMed2006

A selective cyclooxygenase-2 inhibitor decreases transforming growth factor-beta1 synthesis and matrix production in human peritoneal mesothelial cells.

High glucose concentration, which provides the chief driving force in peritoneal dialysis, has been considered to be an important initial factor that contributes to peritoneal thickening and fibrosis. Human peritoneal mesothelial cells (HPMCs) and the expansion of extracellular matrix (ECM) play important roles in the pathological process of peritoneal fibrosis. Peritoneal matrix accumulation is a characteristic of peritoneal fibrosis (PF). Continuous ambulatory peritoneal dialysis (CAPD) patients with upregulation of transforming growth factor-beta1 (TGF-beta1) in their drained effluent show an increased risk of PF. Inhibition of TGF-beta1 expression in human peritoneal mesothelial cells (HPMCs) may provide a potential treatment for PF. sc58236, a highly selective cyclooxygenase-2 (COX-2) inhibitor, reduces proteinuria and mRNA expression of TGF-beta1 and collagen III and IV in the remnant kidney, but their effects on ECM turnover in HPMCs are unknown. The aims of this study were to investigate the effects of sc58236 on TGF-beta1 expression and matrix production in HPMCs. HPMCs were cultured from human omentum by an enzyme digestion method. To examine the effect of sc58236 on TGF-beta1 and ECM secretion, HPMC were incubated in medium F12 with high concentration of D-glucose (4.25%) in the presence and absence of 20 microM sc58236. The mRNA expression of COX-2, TGF-beta1 and collagen I (Col I) were determined by semi-quantification reverse transcription PCR (RT-PCR). Prostaglandin E2 (PGE2) concentration in the culture medium was measured by enzyme-linked immunosorbent assay (ELISA). The protein of TGF-beta1 was determined by ELISA and the activity of TGF-beta1 present in the conditioned media was measured using the mink lung epithelial cell (MLEC) growth inhibition assay. Proteins of COX-2 and Col were determined by Western blot. The results showed that primary cultures of HPMCs do express the mRNA for COX-2 and stimulation of these cells with 4.25% D-glucose induced a marked increase in COX-2 mRNA expression and protein. PGE2 expression was obviously up-regulated with stimulation by 4.25% D-glucose. Addition of 20 microM sc58236 significantly inhibited PGE2 release into the culture medium. mRNA expression and bioactive and total protein of TGF-beta1 and Col I were significantly increased in HPMCs stimulated with 4.25% D-glucose compared to the control group with F12 media, which was reversed in the presence of sc58236 (20 microM). An obvious decrease in TGF-beta1 mRNA expression and bioactive and total protein were found in sc58236 treated groups compared to the group stimulated with 4.25% D-glucose. Exposure of HPMCs to sc58236 reduced Col I secretion. Sc58236 reduces the expression of TGF-beta1 in HPMCs stimulated by 4.25% D-glucose and reduces ECM production through PGE2 production. These studies suggest that sc58236, a highly selective cyclooxygenase-2 (COX-2) inhibitor, may have a specific role in ameliorating the course of progressive peritoneal fibrosis under long-term peritoneal dialysis states.

Cell Division↗

PubMed2006

Synthesis and antitumor evaluation of a novel series of triaminotriazine derivatives.

A series of triaminotriazine derivatives (compounds 5a-f, 6a-x, and 7a-g) was designed, synthesized, and evaluated for their inhibition activities to colorectal cancer (CRC) cell lines (HCT-116 and HT-29). Most of the synthesized compounds demonstrated moderate anti-proliferatory effects on both HCT-116 and HT-29 cell lines at the concentration of 10 microM. The inhibitory activities against HCT-116 and HT-29 cell lines were discussed to develop the structure-activity relationships of this new series. Compounds 6l and 6o exhibited prominent inhibition activities toward HCT-116, with IC50s of 0.76 and 0.92 microM, respectively. The in vivo antitumor studies and pharmacokinetics of compound 6l showed that it might be a promising new hit for further development of antitumor agents.

Antineoplastic Agents↗

PubMed2006

QSAR analyses on avian influenza virus neuraminidase inhibitors using CoMFA, CoMSIA, and HQSAR.

The recent wide spreading of the H5N1 avian influenza virus (AIV) in Asia, Europe and Africa and its ability to cause fatal infections in human has raised serious concerns about a pending global flu pandemic. Neuraminidase (NA) inhibitors are currently the only option for treatment or prophylaxis in humans infected with this strain. However, drugs currently on the market often meet with rapidly emerging resistant mutants and only have limited application as inadequate supply of synthetic material. To dig out helpful information for designing potent inhibitors with novel structures against the NA, we used automated docking, CoMFA, CoMSIA, and HQSAR methods to investigate the quantitative structure-activity relationship for 126 NA inhibitors (NIs) with great structural diversities and wide range of bioactivities against influenza A virus. Based on the binding conformations discovered via molecular docking into the crystal structure of NA, CoMFA and CoMSIA models were successfully built with the cross-validated q (2) of 0.813 and 0.771, respectively. HQSAR was also carried out as a complementary study in that HQSAR technique does not require 3D information of these compounds and could provide a detailed molecular fragment contribution to the inhibitory activity. These models also show clearly how steric, electrostatic, hydrophobicity, and individual fragments affect the potency of NA inhibitors. In addition, CoMFA and CoMSIA field distributions are found to be in well agreement with the structural characteristics of the corresponding binding sites. Therefore, the final 3D-QSAR models and the information of the inhibitor-enzyme interaction should be useful in developing novel potent NA inhibitors.

Amino Acid Sequence↗

PubMed2006

Calculating the jet quenching parameter.

Models of medium-induced radiative parton energy loss account for the strong suppression of high-p(T) hadron spectra in square root of (S)NN=200 GeV Au-Au collisions at BNL RHIC in terms of a single "jet quenching parameter" q. We observe that q can be given a model-independent, nonperturbative, quantum field theoretic definition in terms of the short-distance behavior of a particular lightlike Wilson loop. We then use the anti-de Sitter/conformal-field-theory correspondence to obtain a strong-coupling calculation of q in hot N=4 supersymmetric QCD, finding q(SYM)=26.69 square root of alpha(SYM)N(c)T(3) in the limit in which both N(c) and 4pialpha(SYM)N(c) are large. Thus, at strong coupling q is not proportional to the entropy density s, or to some "number density of scatterers" since, unlike the number of degrees of freedom, q does not grow like N(c)(2).

Journal Article↗

PubMed2006

Engineering mammalian cytochrome P450 2B1 by directed evolution for enhanced catalytic tolerance to temperature and dimethyl sulfoxide.

The previously laboratory-evolved cytochrome P450 2B1 quadruple mutant V183L/F202L/L209A/S334P (QM), which showed enhanced H(2)O(2)-mediated substrate oxidation, has now been shown to exhibit a >3.0-fold decrease in K(m,HOOH) for 7-ethoxy-4-trifluoromethylcoumarin (7-EFC) O-deethylation compared with the parental enzyme L209A. Subsequently, a streamlined random mutagenesis and a high-throughput screening method were developed using QM to screen and select mutants with enhanced tolerance of catalytic activity to temperature and dimethyl sulfoxide (DMSO). Upon screening >3000 colonies, we identified QM/L295H and QM/K236I/D257N with enhanced catalytic tolerance to temperature and DMSO. QM/L295H exhibited higher activity than QM at a broad range of temperatures (35-55 degrees C) and maintained approximately 1.4-fold higher activity than QM at 45 degrees C for 6 h. In addition, QM/L295H showed a significant increase in T(m,app) compared with L209A. QM/L295H and QM/K236I/D257N exhibited higher activity than QM at a broad range of DMSO concentrations (2.5-15%). Furthermore, QM/K236I/D257N/L295H was constructed by combining QM/K236I/D257N with L295H using site-directed mutagenesis and exhibited a >2-fold higher activity than QM at nearly the entire range of DMSO concentrations. In conclusion, in addition to engineering mammalian cytochromes P450 for enhanced activity, directed evolution can also be used to optimize catalytic tolerance to temperature and organic solvent.

Animals↗

PubMed2006

Binding interaction of quercetin-3-beta-galactoside and its synthetic derivatives with SARS-CoV 3CL(pro): structure-activity relationship studies reveal salient pharmacophore features.

The 3C-like protease (3CL(pro)) of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is one of the most promising targets for discovery of drugs against SARS, because of its critical role in the viral life cycle. In this study, a natural compound called quercetin-3-beta-galactoside was identified as an inhibitor of the protease by molecular docking, SPR/FRET-based bioassays, and mutagenesis studies. Both molecular modeling and Q189A mutation revealed that Gln189 plays a key role in the binding. Furthermore, experimental evidence showed that the secondary structure and enzymatic activity of SARS-CoV 3CL(pro) were not affected by the Q189A mutation. With the help of molecular modeling, eight new derivatives of the natural product were designed and synthesized. Bioassay results reveal salient features of the structure-activity relationship of the new compounds: (1) removal of the 7-hydroxy group of the quercetin moiety decreases the bioactivity of the derivatives; (2) acetoxylation of the sugar moiety abolishes inhibitor action; (3) introduction of a large sugar substituent on 7-hydroxy of quercetin can be tolerated; (4) replacement of the galactose moiety with other sugars does not affect inhibitor potency. This study not only reveals a new class of compounds as potential drug leads against the SARS virus, but also provides a solid understanding of the mechanism of inhibition against the target enzyme.

Binding Sites↗