RESUMO
Carbohydrate-active enzymes from the glycoside hydrolase family 9 (GH9) play a key role in processing lignocellulosic biomass. Although the structural features of some GH9 enzymes are known, the molecular mechanisms that drive their interactions with cellulosic substrates remain unclear. To investigate the molecular mechanisms that the two-domain Bacillus licheniformis BlCel9A enzyme utilizes to depolymerize cellulosic substrates, we used a combination of biochemical assays, X-ray crystallography, small-angle X-ray scattering, and molecular dynamics simulations. The results reveal that BlCel9A breaks down cellulosic substrates, releasing cellobiose and glucose as the major products, but is highly inefficient in cleaving oligosaccharides shorter than cellotetraose. In addition, fungal lytic polysaccharide oxygenase (LPMO) TtLPMO9H enhances depolymerization of crystalline cellulose by BlCel9A, while exhibiting minimal impact on amorphous cellulose. The crystal structures of BlCel9A in both apo form and bound to cellotriose and cellohexaose were elucidated, unveiling the interactions of BlCel9A with the ligands and their contribution to substrate binding and products release. MD simulation analysis reveals that BlCel9A exhibits higher interdomain flexibility under acidic conditions, and SAXS experiments indicate that the enzyme flexibility is induced by pH and/or temperature. Our findings provide new insights into BlCel9A substrate specificity and binding, and synergy with the LPMOs.
Assuntos
Celulose , Glicosídeo Hidrolases , Glicosídeo Hidrolases/metabolismo , Espalhamento a Baixo Ângulo , Difração de Raios X , Celulose/química , Carboidratos , Especificidade por SubstratoRESUMO
BACKGROUND: Perillyl alcohol (POH) is a monoterpenoid found in plant essential oils and has been shown to relax murine vessels, but its effect on human vessels remains poorly studied. OBJECTIVE: The study aimed to characterize the effect of POH on human umbilical arteries (HUA). METHODS: Rings of HUA were obtained from uncomplicated patients and suspended in an organ bath for isometric recording. The vasorelaxant effect of POH in HUA was evaluated on basal tone and electromechanical or pharmacomechanical contractions, and possible mechanisms of action were also investigated. RESULTS: POH (1-1000 µM) altered the basal tone of HUA and completely relaxed HUA rings precontracted with KCl (60 mM) or 5-HT (10 µM), obtaining greater potency in the pharmacomechanical pathway (EC50 110.1 µM), suggesting a complex interference in the mobilization of extra- and intracellular Ca2+. POH (1000 µM) inhibited contractions induced by BaCl2 (0.1-30 mM) in a similar way to nifedipine (10 µM), indicating a possible blockade of L-type VOCC. In the presence of potassium channel blockers, tetraethylammonium (1 mM), 4-aminopyridine (1 mM), or glibenclamide (10 µM), an increase in the EC50 value of the POH was observed, suggesting a modulation of the activity of BKCa, KV, and KATP channels. CONCLUSION: The data from this study suggest that POH modulates Ca2+ and K+ ion channels to induce a relaxant response in HUA.
RESUMO
Background: (E,E)-farnesol is a sesquiterpene alcohol derived from plants and animals that exhibits pharmacological properties in the cardiovascular system. However, its effects on human umbilical vessels remain unknown. Purpose: Thus, this study aims to characterize the vasodilatory effect of (E,E)-farnesol in human umbilical arteries (HUA). Study design: The tissue is obtained from pregnant women over 18 years of age, normotensive, and without prepartum complications. After collected, the tissue was segmented and dissected to remove Wharton's jelly and obtain the umbilical arteries segments. Methods: HUA segments were isolated and sectioned into rings that were subjected to isometric tension recordings in an organ bath. Results: (E,E)-farnesol (1 µmol/L to 1 mmol/L) promoted vasodilatory effect in HUA preparations, affecting basal tone, and inhibiting the electromechanical coupling induced by KCl 60 mmol/L with greater potency (EC50 225.3 µmol/L) than the pharmacomechanical coupling induced by 5-HT 10 µmol/L (EC50 363.5 µmol/L). In the absence of extracellular calcium, pharmacomechanical coupling was also abolished, and contractions induced by CaCl2 or BaCl2 were attenuated by (E,E)-farnesol indicating a possible direct inhibition of L-type VOCC as a mechanism of the vasodilatory effect. The vasodilator efficacy of (E,E)-farnesol on reduction of vasocontraction induced by the presence of tetraethylammonium (1 or 10 mmol/L), 4-aminopyridine (1 mmol/L) and glibenclamide (10 µmol/L) suggesting a possible influence of different potassium channels (BKCa, KV and KATP). Conclusion: These results suggest that (E,E)-farnesol may be a promising pharmacological candidate for obstetric hypertensive disorders.
RESUMO
Klebsiella pneumoniae is an opportunistic pathogen, which concerns public health systems worldwide, as multiple antibiotic-resistant strains are frequent. One of its pathogenicity factors is the Type VI Secretion System (T6SS), a macromolecular complex assembled through the bacterial membranes. T6SS injects effector proteins inside target cells. Such effectors confer competitive advantages or modulate the target cell signaling and metabolism to favor bacterial infection. The VgrG protein is a T6SS core component. It may present a variable C-terminal domain carrying an additional effector function. Kp52.145 genome encodes three VgrG proteins, one of them with a C-terminal extension (VgrG4-CTD). VgrG4-CTD is 138 amino acids long, does not contain domains of known function, but is conserved in some Klebsiella, and non-Klebsiella species. To get insights into its function, recombinant VgrG4-CTD was used in pulldown experiments to capture ligands from macrophages and lung epithelial cells. A total of 254 proteins were identified: most of them are ribosomal proteins. Cytoskeleton-associated and proteins involved in the phagosome maturation pathway were also identified. We further showed that VgrG4-CTD binds actin and induces actin remodeling in macrophages. This study presents novel clues on the role of K. pneumoniae T6SS in pathogenesis.
Assuntos
Klebsiella pneumoniae , Sistemas de Secreção Tipo VI , Citoesqueleto de Actina/metabolismo , Actinas , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Klebsiella pneumoniae/genética , Klebsiella pneumoniae/metabolismo , Sistemas de Secreção Tipo VI/genética , Sistemas de Secreção Tipo VI/metabolismo , Fatores de VirulênciaRESUMO
Fungi cellulases are used to degrade cellulose-containing biomass for bioethanol production. Industrial cellulases such as Cel7A from Trichoderma reesei (TrCel7A) are critical in this process. Thus, the understanding of structure and dynamics is crucial for engineering variants with improved cellulolytic activity. This cellulase consists of two domains connected by a flexible and highly glycosylated linker. However, the linker flexibility has hindered the determination of Cel7A complete structure. Herein, based on atomic and sparse data, we applied integrative modelling to build a model of the complete enzyme structure. Next, through simulations, we studied the glycosylation effects on the structure and dynamics of a solubilized TrCel7A. Essential dynamics analysis showed that O-glycosylation in the linker led to the stabilization of protein overall dynamics. O-linked glycans seem to restrict protein dihedral angles distribution in this region, selecting more elongated conformations. Besides the reduced flexibility, functional interdomain motions occurred in a more concerted way in the glycosylated system. In contrast, in the absence of glycosylation, we observed vast conformational plasticity with the functional domains frequently collapsing. We report here evidence that targeting Cel7A linker flexibility by point mutations including modification of glycosylation sites could be a promising design strategy to improve cellulase activity.
Assuntos
Celulase/química , Modelos Moleculares , Trichoderma/enzimologia , Proteínas Fúngicas/química , Glicosilação , Conformação ProteicaRESUMO
Gallic acid is a polyphenolic compost appointed to interfere with neoplastic cells behavior. Evidence suggests an important role of leptin in carcinogenesis pathways, inducing a proliferative phenotype. We investigated the potential of gallic acid to modulate leptin-induced cell proliferation and migration of oral squamous cell carcinoma cell lines. The gallic acid effect on leptin secretion by oral squamous cell carcinoma cells, as well as the underlying molecular mechanisms, was also assessed. For this, we performed proliferation, migration, immunocytochemical and qPCR assays. The expression levels of cell migration-related genes (MMP2, MMP9, Col1A1, and E-cadherin), angiogenesis (HIF-1α, mir210), leptin signaling (LepR, p44/42 MAPK), apoptosis (casp-3), and secreted leptin levels by oral squamous cell carcinoma cells were also measured. Gallic acid decreased proliferation and migration of leptin-treated oral squamous cell carcinoma cells, and reduced mRNA expression of MMP2, MMP9, Col1A1, mir210, but did not change HIF-1α. Gallic acid decreased levels of leptin secreted by oral squamous cell carcinoma cells, accordingly with downregulation of p44/42 MAPK expression. Thus, gallic acid appears to break down neoplastic phenotype of oral squamous cell carcinoma cells by interfering with leptin pathway.
Assuntos
Carcinoma de Células Escamosas/patologia , Movimento Celular/efeitos dos fármacos , Ácido Gálico/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Leptina/metabolismo , Carcinoma de Células Escamosas/tratamento farmacológico , Carcinoma de Células Escamosas/genética , Linhagem Celular Tumoral , Movimento Celular/genética , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Regulação Neoplásica da Expressão Gênica/genética , HumanosRESUMO
New strategies to control Leishmania disease demand an extensive knowledge about several aspects of infection including the understanding of its molecular events. In murine models, cysteine proteinase B from Leishmania amazonensis promotes regulation of immune response, and fragments from its C-terminus extension (cyspep) can play a decisive role in the host-parasite interaction. The interaction between cyspep-derived peptides and major histocompatibility complex (MHC) proteins is a crucial factor in Leishmania infections. Seven cyspep-derived peptides, previously identified as capable of interacting with H-2 (murine) MHC class I proteins, were studied in this work. We established a protocol to simulate the unbinding of these peptides from the cleft of H-2 receptors. From the simulations, we estimated the corresponding free energy of dissociation (ΔGd ) and described the molecular events that occur during the exit of peptides from the cleft. To test the reliability of this method, we first applied it to a calibration set of four crystallographic MHC/peptide complexes. Next, we explored the unbinding of the seven complexes mentioned above. Results were consistent with ΔGd values obtained from surface plasmon resonance (SPR) experiments. We also identified some of the primary interactions between peptides and H-2 receptors, and we detected three regions of influence for the interaction. This pattern was systematically observed for the peptides and helped determine a minimum distance for the real interaction between peptides and H-2 proteins occurring at â¼ 25 Å.
Assuntos
Cisteína Proteases/química , Epitopos/química , Antígenos de Histocompatibilidade Classe I/química , Leishmania braziliensis/química , Peptídeos/química , Proteínas de Protozoários/química , Sequência de Aminoácidos , Animais , Cristalografia por Raios X , Cisteína Proteases/genética , Cisteína Proteases/imunologia , Epitopos/genética , Epitopos/imunologia , Expressão Gênica , Antígenos de Histocompatibilidade Classe I/genética , Antígenos de Histocompatibilidade Classe I/imunologia , Leishmania braziliensis/patogenicidade , Leishmaniose Cutânea/imunologia , Leishmaniose Cutânea/parasitologia , Camundongos , Simulação de Dinâmica Molecular , Peptídeos/genética , Peptídeos/imunologia , Ligação Proteica , Dobramento de Proteína , Domínios e Motivos de Interação entre Proteínas , Estrutura Secundária de Proteína , Proteínas de Protozoários/genética , Proteínas de Protozoários/imunologia , Ressonância de Plasmônio de Superfície , TermodinâmicaRESUMO
The drugs against tropical neglected diseases, especially Chagas' Disease, were launched more than 30 years ago, and the development of resistance requires the discovery of new and more effective chemotherapeutic agents. Trypanosoma cruzi has a redox enzyme called trypanothione reductase which was successfully inhibited for peptide derivatives (McKie et al., Amino Acids, 2001, 20: 145). This work aims at studying the mechanism of inhibition of this enzyme through molecular dynamics simulations and evaluating the behavior of some derivatives when inhibiting this protein. We should affirm that any particular molecular dynamics analysis tools (Hbond pattern, 3-D root-mean-square deviation, solvent accessible surface area, etc.) cannot be used apart from the others to justify completely these peptides inhibitory patterns. Based on our results, we reproduced the experimental data and, moreover, we discriminated against a new site in enzyme aperture, which can assist the development of powerful inhibitors against trypanothione reductase enzyme.
Assuntos
NADH NADPH Oxirredutases/metabolismo , Peptídeos/química , Peptídeos/farmacologia , Tripanossomicidas/química , Tripanossomicidas/farmacologia , Trypanosoma cruzi/enzimologia , Domínio Catalítico , Doença de Chagas/tratamento farmacológico , Doença de Chagas/enzimologia , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Humanos , Ligação de Hidrogênio , Simulação de Acoplamento Molecular , NADH NADPH Oxirredutases/química , Trypanosoma cruzi/químicaRESUMO
Cellulases from thermophiles are capable of cleaving sugar chains from cellulose efficiently at high temperatures. The thermo-resistant Cel9A-68 cellulase possesses two important domains: CBM and a catalytic domain connected by a Pro/Ser/Thr rich linker. These domains act cooperatively to allow efficient catalysis. Despite exhaustive efforts to characterize cellulase binding and mechanism of action, a detailed description of the cellulose intrinsic flexibility is still lacking. From computational simulations we studied the temperature influence on the enzyme plasticity, prior to substrate binding. Interestingly, we observed an enhancement of collective motions at high temperatures. These motions are the most representative and describe an intrinsic hinge bending transition. A detailed analysis of these motions revealed an interdomain approximation where D459 and G460, located at the linker region, are the hinge residues. Therefore, we propose a new putative site for mutagenesis targeting the modulation of such conformational transition that may be crucial for activity.