Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 33.362
Filtrar
1.
Nat Commun ; 11(1): 4955, 2020 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-33009385

RESUMO

The light-harvesting-reaction center complex (LH1-RC) from the purple phototrophic bacterium Thiorhodovibrio strain 970 exhibits an LH1 absorption maximum at 960 nm, the most red-shifted absorption for any bacteriochlorophyll (BChl) a-containing species. Here we present a cryo-EM structure of the strain 970 LH1-RC complex at 2.82 Å resolution. The LH1 forms a closed ring structure composed of sixteen pairs of the αß-polypeptides. Sixteen Ca ions are present in the LH1 C-terminal domain and are coordinated by residues from the αß-polypeptides that are hydrogen-bonded to BChl a. The Ca2+-facilitated hydrogen-bonding network forms the structural basis of the unusual LH1 redshift. The structure also revealed the arrangement of multiple forms of α- and ß-polypeptides in an individual LH1 ring. Such organization indicates a mechanism of interplay between the expression and assembly of the LH1 complex that is regulated through interactions with the RC subunits inside.


Assuntos
Cálcio/metabolismo , Microscopia Crioeletrônica , Complexos de Proteínas Captadores de Luz/ultraestrutura , Peptídeos/metabolismo , Fotossíntese , Sequência de Aminoácidos , Bacterioclorofila A/metabolismo , Sítios de Ligação , Chromatiaceae/metabolismo , Detergentes/química , Dimerização , Complexos de Proteínas Captadores de Luz/química , Complexos de Proteínas Captadores de Luz/metabolismo , Lipídeos/química , Peptídeos/química , Quinonas/química
2.
Nat Commun ; 11(1): 4554, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917865

RESUMO

Non-ribosomal peptide synthetase (NRPS) enzymes form modular assembly-lines, wherein each module governs the incorporation of a specific monomer into a short peptide product. Modules are comprised of one or more key domains, including adenylation (A) domains, which recognise and activate the monomer substrate; condensation (C) domains, which catalyse amide bond formation; and thiolation (T) domains, which shuttle reaction intermediates between catalytic domains. This arrangement offers prospects for rational peptide modification via substitution of substrate-specifying domains. For over 20 years, it has been considered that C domains play key roles in proof-reading the substrate; a presumption that has greatly complicated rational NRPS redesign. Here we present evidence from both directed and natural evolution studies that any substrate-specifying role for C domains is likely to be the exception rather than the rule, and that novel non-ribosomal peptides can be generated by substitution of A domains alone. We identify permissive A domain recombination boundaries and show that these allow us to efficiently generate modified pyoverdine peptides at high yields. We further demonstrate the transferability of our approach in the PheATE-ProCAT model system originally used to infer C domain substrate specificity, generating modified dipeptide products at yields that are inconsistent with the prevailing dogma.


Assuntos
Monofosfato de Adenosina/metabolismo , Peptídeos/química , Peptídeos/metabolismo , Domínios Proteicos , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Embaralhamento de DNA , Modelos Moleculares , Família Multigênica , Oligopeptídeos/química , Oligopeptídeos/metabolismo , Peptídeo Sintases/genética , Peptídeo Sintases/metabolismo , Conformação Proteica , Pseudomonas , Especificidade por Substrato
3.
Viruses ; 12(9)2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32971895

RESUMO

Coronaviruses (CoVs) are enveloped, positive sense, single strand RNA viruses that cause respiratory, intestinal and neurological diseases in mammals and birds. Following replication, CoVs assemble on intracellular membranes including the endoplasmic reticulum Golgi intermediate compartment (ERGIC) where the envelope protein (E) functions in virus assembly and release. In consequence, E potentially contains membrane-modifying peptides. To search for such peptides, the E coding sequence of Mouse Hepatitis Virus (MHV) was inspected for its amino acid conservation, proximity to the membrane and/or predicted amphipathic helices. Peptides identified in silico were synthesized and tested for membrane-modifying activity in the presence of giant unilamellar vesicles (GUVs) consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), sphingomyelin and cholesterol. To confirm the presence of membrane binding peptides identified in the context of a full-length E protein, the wild type and a number of mutants in the putative membrane binding peptide were expressed in Lenti-X-293T mammalian and insect cells, and the distribution of E antigen within the expressing cell was assessed. Our data identify a role for the post-transmembrane region of MHV E in membrane binding.


Assuntos
Vírus da Hepatite Murina/química , Peptídeos/química , Proteínas do Envelope Viral/química , Sequência de Aminoácidos , Animais , Linhagem Celular , Infecções por Coronavirus , Humanos , Membranas Intracelulares/metabolismo , Camundongos , Vírus da Hepatite Murina/genética , Vírus da Hepatite Murina/metabolismo , Mutação , Peptídeos/síntese química , Peptídeos/metabolismo , Células Sf9 , Spodoptera , Lipossomas Unilamelares/metabolismo , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/metabolismo
4.
PLoS One ; 15(8): e0233247, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32857759

RESUMO

Poly(glycine-alanine) (polyGA) is one of the polydipeptides expressed in Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis 1 caused by C9ORF72 mutations and accumulates as inclusion bodies in the brain of patients. Superficially these inclusions are similar to those formed by polyglutamine (polyQ)-expanded Huntingtin exon 1 (Httex1) in Huntington's disease. Both have been reported to form an amyloid-like structure suggesting they might aggregate via similar mechanisms and therefore recruit the same repertoire of endogenous proteins. When co-expressed in the same cell, polyGA101 and Httex1(Q97) inclusions adopted immiscible phases suggesting different endogenous proteins would be enriched. Proteomic analyses identified 822 proteins in the inclusions. Only 7 were specific to polyGA and 4 specific to Httex1(Q97). Quantitation demonstrated distinct enrichment patterns for the proteins not specific to each inclusion type (up to ~8-fold normalized to total mass). The proteasome, microtubules, TriC chaperones, and translational machinery were enriched in polyGA aggregates, whereas Dnaj chaperones, nuclear envelope and RNA splicing proteins were enriched in Httex1(Q97) aggregates. Both structures revealed a collection of folding and degradation machinery including proteins in the Httex1(Q97) aggregates that are risk factors for other neurodegenerative diseases involving protein aggregation when mutated, which suggests a convergence point in the pathomechanisms of these diseases.


Assuntos
Corpos de Inclusão/metabolismo , Peptídeos/metabolismo , Proteínas/metabolismo , Animais , Proteína C9orf72/genética , Proteína C9orf72/metabolismo , Linhagem Celular , Éxons , Humanos , Proteína Huntingtina/genética , Proteína Huntingtina/metabolismo , Corpos de Inclusão/genética , Corpos de Inclusão/patologia , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Camundongos , Microscopia Confocal , Mutação , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Doenças Neurodegenerativas/genética , Doenças Neurodegenerativas/metabolismo , Doenças Neurodegenerativas/patologia , Peptídeos/genética , Agregação Patológica de Proteínas/genética , Agregação Patológica de Proteínas/metabolismo , Agregação Patológica de Proteínas/patologia , Proteínas/genética , Proteólise , Proteoma/genética , Proteoma/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Fatores de Risco , Solubilidade
5.
Nature ; 585(7824): 256-260, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32848244

RESUMO

Temperature controls plant growth and development, and climate change has already altered the phenology of wild plants and crops1. However, the mechanisms by which plants sense temperature are not well understood. The evening complex is a major signalling hub and a core component of the plant circadian clock2,3. The evening complex acts as a temperature-responsive transcriptional repressor, providing rhythmicity and temperature responsiveness to growth through unknown mechanisms2,4-6. The evening complex consists of EARLY FLOWERING 3 (ELF3)4,7, a large scaffold protein and key component of temperature sensing; ELF4, a small α-helical protein; and LUX ARRYTHMO (LUX), a DNA-binding protein required to recruit the evening complex to transcriptional targets. ELF3 contains a polyglutamine (polyQ) repeat8-10, embedded within a predicted prion domain (PrD). Here we find that the length of the polyQ repeat correlates with thermal responsiveness. We show that ELF3 proteins in plants from hotter climates, with no detectable PrD, are active at high temperatures, and lack thermal responsiveness. The temperature sensitivity of ELF3 is also modulated by the levels of ELF4, indicating that ELF4 can stabilize the function of ELF3. In both Arabidopsis and a heterologous system, ELF3 fused with green fluorescent protein forms speckles within minutes in response to higher temperatures, in a PrD-dependent manner. A purified fragment encompassing the ELF3 PrD reversibly forms liquid droplets in response to increasing temperatures in vitro, indicating that these properties reflect a direct biophysical response conferred by the PrD. The ability of temperature to rapidly shift ELF3 between active and inactive states via phase transition represents a previously unknown thermosensory mechanism.


Assuntos
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas Priônicas/química , Temperatura , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo , Aclimatação/fisiologia , Arabidopsis/química , Temperatura Alta , Modelos Moleculares , Peptídeos/metabolismo , Transição de Fase , Domínios Proteicos , Proteínas Repressoras/química , Proteínas Repressoras/metabolismo
6.
Nat Commun ; 11(1): 4252, 2020 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-32843628

RESUMO

The 2019 novel respiratory virus (SARS-CoV-2) causes COVID-19 with rapid global socioeconomic disruptions and disease burden to healthcare. The COVID-19 and previous emerging virus outbreaks highlight the urgent need for broad-spectrum antivirals. Here, we show that a defensin-like peptide P9R exhibited potent antiviral activity against pH-dependent viruses that require endosomal acidification for virus infection, including the enveloped pandemic A(H1N1)pdm09 virus, avian influenza A(H7N9) virus, coronaviruses (SARS-CoV-2, MERS-CoV and SARS-CoV), and the non-enveloped rhinovirus. P9R can significantly protect mice from lethal challenge by A(H1N1)pdm09 virus and shows low possibility to cause drug-resistant virus. Mechanistic studies indicate that the antiviral activity of P9R depends on the direct binding to viruses and the inhibition of virus-host endosomal acidification, which provides a proof of concept that virus-binding alkaline peptides can broadly inhibit pH-dependent viruses. These results suggest that the dual-functional virus- and host-targeting P9R can be a promising candidate for combating pH-dependent respiratory viruses.


Assuntos
Antivirais/farmacologia , Coronavirus/efeitos dos fármacos , Vírus da Influenza A/efeitos dos fármacos , Peptídeos/farmacologia , Sequência de Aminoácidos , Animais , Antivirais/química , Antivirais/metabolismo , Antivirais/uso terapêutico , Linhagem Celular , Endossomos/química , Endossomos/efeitos dos fármacos , Feminino , Humanos , Concentração de Íons de Hidrogênio , Vírus da Influenza A/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Infecções por Orthomyxoviridae/tratamento farmacológico , Infecções por Orthomyxoviridae/metabolismo , Peptídeos/química , Peptídeos/metabolismo , Peptídeos/uso terapêutico , Ligação Proteica , Conformação Proteica , Rhinovirus/efeitos dos fármacos , Rhinovirus/metabolismo , Carga Viral/efeitos dos fármacos , Replicação Viral/efeitos dos fármacos
7.
Nat Commun ; 11(1): 4278, 2020 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-32855388

RESUMO

Activation and migration of endogenous mesenchymal stromal cells (MSCs) are critical for bone regeneration. Here, we report a combinational peptide screening strategy for rapid discovery of ligands that not only bind strongly to osteogenic progenitor cells (OPCs) but also stimulate osteogenic cell Akt signaling in those OPCs. Two lead compounds are discovered, YLL3 and YLL8, both of which increase osteoprogenitor osteogenic differentiation in vitro. When given to normal or osteopenic mice, the compounds increase mineral apposition rate, bone formation, bone mass, and bone strength, as well as expedite fracture repair through stimulated endogenous osteogenesis. When covalently conjugated to alendronate, YLLs acquire an additional function resulting in a "tri-functional" compound that: (i) binds to OPCs, (ii) targets bone, and (iii) induces "pro-survival" signal. These bone-targeted, osteogenic peptides are well suited for current tissue-specific therapeutic paradigms to augment the endogenous osteogenic cells for bone regeneration and the treatment of bone loss.


Assuntos
Anabolizantes/farmacologia , Fraturas Ósseas/tratamento farmacológico , Osteogênese/efeitos dos fármacos , Peptídeos/farmacologia , Células-Tronco/efeitos dos fármacos , Anabolizantes/química , Animais , Calcificação Fisiológica/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Células Cultivadas , Feminino , Fraturas Ósseas/patologia , Humanos , Masculino , Células-Tronco Mesenquimais/efeitos dos fármacos , Células-Tronco Mesenquimais/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Orquiectomia , Osteogênese/fisiologia , Ovariectomia , Peptídeos/química , Peptídeos/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Técnicas de Síntese em Fase Sólida , Células-Tronco/citologia
8.
Protein Sci ; 29(10): 2038-2042, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32822073

RESUMO

The Envelope protein (E) is one of the four structural proteins encoded by the genome of SARS-CoV and SARS-CoV-2 Coronaviruses. It is an integral membrane protein, highly expressed in the host cell, which is known to have an important role in Coronaviruses maturation, assembly and virulence. The E protein presents a PDZ-binding motif at its C-terminus. One of the key interactors of the E protein in the intracellular environment is the PDZ containing protein PALS1. This interaction is known to play a key role in the SARS-CoV pathology and suspected to affect the integrity of the lung epithelia. In this paper we measured and compared the affinity of peptides mimicking the E protein from SARS-CoV and SARS-CoV-2 for the PDZ domain of PALS1, through equilibrium and kinetic binding experiments. Our results support the hypothesis that the increased virulence of SARS-CoV-2 compared to SARS-CoV may rely on the increased affinity of its Envelope protein for PALS1.


Assuntos
Betacoronavirus/metabolismo , Infecções por Coronavirus/metabolismo , Proteínas de Membrana/metabolismo , Núcleosídeo-Fosfato Quinase/metabolismo , Pneumonia Viral/metabolismo , Vírus da SARS/metabolismo , Síndrome Respiratória Aguda Grave/metabolismo , Proteínas do Envelope Viral/metabolismo , Sequência de Aminoácidos , Betacoronavirus/química , Sítios de Ligação , Infecções por Coronavirus/virologia , Humanos , Proteínas de Membrana/química , Modelos Moleculares , Núcleosídeo-Fosfato Quinase/química , Domínios PDZ , Pandemias , Peptídeos/química , Peptídeos/metabolismo , Pneumonia Viral/virologia , Ligação Proteica , Vírus da SARS/química , Síndrome Respiratória Aguda Grave/virologia , Proteínas do Envelope Viral/química
9.
Int J Nanomedicine ; 15: 4289-4309, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32606678

RESUMO

Objective: To construct prostate-specific membrane antigen (PSMA)-targeting, indocyanine green (ICG)-loaded nanobubbles (NBs) for multimodal (ultrasound, photoacoustic and fluorescence) imaging of prostate cancer. Methods: The mechanical oscillation method was used to prepare ICG-loaded photoacoustic NBs (ICG NBs). Then, PSMA-binding peptides were connected to the surface of ICG NBs using the biotin-avidin method to make targeted photoacoustic NBs, namely, PSMAP/ICG NBs. Their particle sizes, zeta potentials, and in vitro ultrasound, photoacoustic and fluorescence imaging were examined. Confocal laser scanning microscopy and flow cytometry were used to detect the binding ability of the PSMAP/ICG NBs to PSMA-positive LNCaP cells, C4-2 cells, and PSMA-negative PC-3 cells. The multimodal imaging effects of PSMAP/ICG NBs and ICG NBs were compared in nude mouse tumor xenografts. Results: The particle size of the PSMAP/ICG NBs was approximately 457.7 nm, and the zeta potential was approximately -23.5 mV. Both confocal laser scanning microscopy and flow cytometry confirmed that the PSMAP/ICG NBs could specifically bind to both LNCaP and C4-2 cells, but they rarely bound to PC-3 cells. The ultrasound, photoacoustic and fluorescence imaging intensities of the PSMAP/ICG NBs in vitro positively correlated with their concentrations. The ultrasound and photoacoustic imaging effects of the PSMAP/ICG NBs in LNCaP and C4-2 tumor xenografts were significantly enhanced compared with those in PC-3 tumor xenografts, which were characterized by a significantly increased duration of ultrasound enhancement and heightened photoacoustic signal intensity (P < 0.05). Fluorescence imaging showed that PSMAP/ICG NBs could accumulate in LNCaP and C4-2 tumor xenografts for a relatively long period. Conclusion: The targeted photoacoustic nanobubbles prepared in this study can specifically bind to PSMA-positive prostate cancer cells and have the ability to enhance ultrasound, photoacoustic and fluorescence imaging of PSMA-positive tumor xenografts. Photoacoustic imaging could visually display the intensity of the red photoacoustic signal in the tumor region, providing a more intuitive imaging modality for targeted molecular imaging. This study presents a potential multimodal contrast agent for the accurate diagnosis and assessment of prostate cancer.


Assuntos
Verde de Indocianina/química , Nanopartículas/química , Imagem Óptica , Técnicas Fotoacústicas , Neoplasias da Próstata/diagnóstico por imagem , Ultrassonografia , Animais , Linhagem Celular Tumoral , Meios de Contraste/química , Fluorescência , Humanos , Masculino , Camundongos Nus , Nanopartículas/ultraestrutura , Tamanho da Partícula , Peptídeos/metabolismo , Antígeno Prostático Específico/metabolismo , Neoplasias da Próstata/terapia , Ligação Proteica
10.
BMC Bioinformatics ; 21(1): 279, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32615972

RESUMO

BACKGROUND: Immunotherapy is a promising route towards personalized cancer treatment. A key algorithmic challenge in this process is to decide if a given peptide (neoepitope) binds with the major histocompatibility complex (MHC). This is an active area of research and there are many MHC binding prediction algorithms that can predict the MHC binding affinity for a given peptide to a high degree of accuracy. However, most of the state-of-the-art approaches make use of complicated training and model selection procedures, are restricted to peptides of a certain length and/or rely on heuristics. RESULTS: We put forward USMPep, a simple recurrent neural network that reaches state-of-the-art approaches on MHC class I binding prediction with a single, generic architecture and even a single set of hyperparameters both on IEDB benchmark datasets and on the very recent HPV dataset. Moreover, the algorithm is competitive for a single model trained from scratch, while ensembling multiple regressors and language model pretraining can still slightly improve the performance. The direct application of the approach to MHC class II binding prediction shows a solid performance despite of limited training data. CONCLUSIONS: We demonstrate that competitive performance in MHC binding affinity prediction can be reached with a standard architecture and training procedure without relying on any heuristics.


Assuntos
Algoritmos , Antígenos de Histocompatibilidade Classe II/metabolismo , Antígenos de Histocompatibilidade Classe I/metabolismo , Modelos Genéticos , Alelos , Área Sob a Curva , Sequência de Bases , Bases de Dados Genéticas , Humanos , Peptídeos/metabolismo , Ligação Proteica , Curva ROC
11.
Proc Natl Acad Sci U S A ; 117(32): 19399-19407, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32719124

RESUMO

The source proteins from which CD8+ T cell-activating peptides are derived remain enigmatic. Glycoproteins are particularly challenging in this regard owing to several potential trafficking routes within the cell. By engineering a glycoprotein-derived epitope to contain an N-linked glycosylation site, we determined that optimal CD8+ T cell expansion and function were induced by the peptides that are rapidly produced from the exceedingly minor fraction of protein mislocalized to the cytosol. In contrast, peptides derived from the much larger fraction that undergoes translocation and quality control are produced with delayed kinetics and induce suboptimal CD8+ T cell responses. This dual system of peptide generation enhances CD8+ T cell participation in diversifying both antigenicity and the kinetics of peptide display.


Assuntos
Apresentação do Antígeno , Linfócitos T CD8-Positivos/imunologia , Epitopos/imunologia , Epitopos/metabolismo , Animais , Linhagem Celular , Citosol/metabolismo , Retículo Endoplasmático/metabolismo , Glicosilação , Antígenos de Histocompatibilidade Classe I/metabolismo , Cinética , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Peptídeos/genética , Peptídeos/metabolismo , Sinais Direcionadores de Proteínas/genética
12.
Nat Commun ; 11(1): 3314, 2020 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-32620861

RESUMO

The amyloid conformation can be adopted by a variety of sequences, but the precise boundaries of amyloid sequence space are still unclear. The currently charted amyloid sequence space is strongly biased towards hydrophobic, beta-sheet prone sequences that form the core of globular proteins and by Q/N/Y rich yeast prions. Here, we took advantage of the increasing amount of high-resolution structural information on amyloid cores currently available in the protein databank to implement a machine learning approach, named Cordax (https://cordax.switchlab.org), that explores amyloid sequence beyond its current boundaries. Clustering by t-Distributed Stochastic Neighbour Embedding (t-SNE) shows how our approach resulted in an expansion away from hydrophobic amyloid sequences towards clusters of lower aliphatic content and higher charge, or regions of helical and disordered propensities. These clusters uncouple amyloid propensity from solubility representing sequence flavours compatible with surface-exposed patches in globular proteins, functional amyloids or sequences associated to liquid-liquid phase transitions.


Assuntos
Algoritmos , Amiloide/química , Proteínas Amiloidogênicas/química , Modelos Químicos , Peptídeos/química , Amiloide/metabolismo , Proteínas Amiloidogênicas/metabolismo , Amiloidose/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Aprendizado de Máquina , Peptídeos/metabolismo , Conformação Proteica , Engenharia de Proteínas/métodos , Solubilidade
13.
J Chromatogr A ; 1625: 461237, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709313

RESUMO

The quest for ligands alternative to Protein A for the purification of monoclonal antibodies (mAbs) has been pursued for almost three decades. Yet, the IgG-binding peptides known to date still fall short of the host cell protein (HCP) logarithmic removal value (LRV) set by Protein A media (2.5-3.1). In this study, we present an integrated computational-experimental approach leading to the discovery of peptide ligands that provide HCP LRVs on par with Protein A. First, the screening of 60,000 peptide variants was performed using a high-throughput search algorithm to identify sequences that ensure IgG affinity binding. Select sequences WQRHGI, MWRGWQ, RHLGWF, and GWLHQR were then negatively screened in silico against a panel of model HCPs to ensure the selection of peptides with high binding selectivity. Candidate ligands WQRHGI and MWRGWQ were conjugated to chromatographic resins and characterized by isothermal binding and breakthrough assays to quantify static and dynamic binding capacity (Qmax and DBC10%), respectively. The resulting Qmax were 52.6 mg of IgG per mL of adsorbent for WQRHGI and 57.48 mg/mL for MWRGWQ, while the DBC10% (2 minutes residence time) were 30.1 mg/mL for WQRHGI and 36.4 mg/mL for MWRGWQ. Evaluation of the peptides by isothermal titration calorimetry (ITC) confirmed the binding energy predicted in silico, and an amino acid scanning study corroborated the affinity-like binding activity of the peptides. WQRHGI-WorkBeads resin was finally characterized by purification of a monoclonal antibody from a Chinese Hamster Ovary (CHO) cell culture harvest, affording a remarkable HCP LRV of 2.7, and consistent product yield and purity over 100 chromatographic cycles. These results demonstrate the potential of WQRHGI as an effective alternative to Protein A for antibody purification.


Assuntos
Anticorpos Monoclonais/isolamento & purificação , Cromatografia de Afinidade/métodos , Peptídeos/química , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/metabolismo , Células CHO , Cricetinae , Cricetulus , Imunoglobulina G/isolamento & purificação , Imunoglobulina G/metabolismo , Ligantes , Peptídeos/síntese química , Peptídeos/metabolismo , Ligação Proteica , Proteína Estafilocócica A/química , Proteína Estafilocócica A/metabolismo
14.
Food Chem ; 332: 127388, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32603918

RESUMO

Peptidyl post-translational modifications (PTMs) could influence the final quality of processed meat. In this study, the peptide oxidative phenomena in Spanish dry-cured ham (Biceps femoris muscle) was evaluated at different ripening times (9, 12, 15, 18 and 24 months of processing) evidencing interactions amongst the lipid and protein oxidation, major peptidyl PTMs and the release of free amino acids (FAAs). Results showed that 12 months of processing enabled the most abundant protein-bound carbonyls, while TBARS value was significantly favored (p < 0.001) by ripening. However, FAAs were still intensively generated during overall ripening. Peptidomics and chemometrics further revealed that proteolysis mostly hampered the oxidized peptides rather than the deamidated ones during ripening. Myosin light chain (MYL1 and MYL3) showed high oxidative susceptibility owing to peptidyl methionine and proline oxidation as well as acetaldehyde adduct formation on lysine or histidine residues.


Assuntos
Produtos da Carne/análise , Cadeias Leves de Miosina/metabolismo , Peptídeos/análise , Aminoácidos/análise , Animais , Cromatografia Líquida de Alta Pressão , Dipeptídeos/análise , Peroxidação de Lipídeos , Cadeias Leves de Miosina/química , Oxirredução , Peptídeos/metabolismo , Análise de Componente Principal , Processamento de Proteína Pós-Traducional , Suínos , Espectrometria de Massas em Tandem
15.
Toxicol Lett ; 332: 146-154, 2020 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-32683294

RESUMO

Occludin is an important tight junction (TJ) protein in pulmonary epithelial cells. In this study, we identified changes in occludin in arsenic-induced lung injury in vivo and in vitro. Upon intratracheal instillation with arsenic trioxide (As2O3) at a daily dose of 30 µg/kg for 1 week, levels of occludin mRNA and protein expression decreased significantly in mouse lung tissue. Levels of occludin mRNA and protein expression in BEAS-2B cells were reduced upon exposure to As2O3 in a concentration- and time-dependent manner. In addition, exposure to As2O3 significantly increased expression of p-p38, p-ERK1/2, p-ELK1, and MLCK in mouse lung tissue and BEAS-2B cells. Treatment with As2O3 induced oxidative stress in mouse lung tissue and BEAS-2B cells. In BEAS-2B cells, exposure to As2O3 reduced transepithelial resistance, which was partially restored with N-acetyl-cysteine (NAC) treatment. Reduced expression of occludin mRNA and protein induced by As2O3 was entirely restored with NAC and resveratrol. However, SB203580, PD98059, and ML-7 partially blocked As2O3-induced occludin reduction in BEAS-2B cells. These results indicate that As2O3 inhibits occludin expression in vivo and in vitro at least partially via the ROS/ERK/ELK1/MLCK and ROS/p38 MAPK signaling pathways.


Assuntos
Arsenitos/toxicidade , Pulmão/metabolismo , Ocludina/biossíntese , Transdução de Sinais/efeitos dos fármacos , Animais , Linhagem Celular , Regulação para Baixo/efeitos dos fármacos , Glutationa/metabolismo , Humanos , Pulmão/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ocludina/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Peptídeos/efeitos dos fármacos , Peptídeos/metabolismo , Espécies Reativas de Oxigênio , Superóxido Dismutase/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/efeitos dos fármacos
16.
Proc Natl Acad Sci U S A ; 117(29): 17211-17220, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32611811

RESUMO

The bacterial second messenger cyclic diguanylate (c-di-GMP) regulates a wide range of cellular functions from biofilm formation to growth and survival. Targeting a second-messenger network is challenging because the system involves a multitude of components with often overlapping functions. Here, we present a strategy to intercept c-di-GMP signaling pathways by directly targeting the second messenger. For this, we developed a c-di-GMP-sequestering peptide (CSP) that was derived from a CheY-like c-di-GMP effector protein. CSP binds c-di-GMP with submicromolar affinity. The elucidation of the CSP⋅c-di-GMP complex structure by NMR identified a linear c-di-GMP-binding motif, in which a self-intercalated c-di-GMP dimer is tightly bound by a network of H bonds and π-stacking interactions involving arginine and aromatic residues. Structure-based mutagenesis yielded a variant with considerably higher, low-nanomolar affinity, which subsequently was shortened to 19 residues with almost uncompromised affinity. We demonstrate that endogenously expressed CSP intercepts c-di-GMP signaling and effectively inhibits biofilm formation in Pseudomonas aeruginosa, the most widely used model for serious biofilm-associated medical implications.


Assuntos
Proteínas de Bactérias/metabolismo , GMP Cíclico/análogos & derivados , GMP Cíclico/metabolismo , Peptídeos/metabolismo , Sistemas do Segundo Mensageiro , Transdução de Sinais , Biofilmes/crescimento & desenvolvimento , Proteínas de Escherichia coli , Modelos Moleculares , Mutagênese , Peptídeos/química , Peptídeos/genética , Mutação Puntual , Conformação Proteica , Domínios Proteicos , Domínios e Motivos de Interação entre Proteínas , Pseudomonas aeruginosa/metabolismo
17.
Food Chem ; 331: 127216, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32650230

RESUMO

The effects of ultrasound working modes using multi-mode S-type ultrasound on the preparation of bioactive peptide from rice protein (RP) were studied with the ACE inhibitory activity of protein-hydrolysate after gastrointestinal simulated digestion as the index. The structure characterizations of protein and enzymolysis products were also studied. Results showed that all the ultrasound working modes pretreatment increased the ACE inhibitory activity significantly (p < 0.05) and 20/40 kHz dual-frequency ultrasound showed the most significant impact, which increased by 38.28% and 27.47% compared to control and ultrasound cleaning machine, respectively. After pretreated by 20/40 kHz dual-frequency ultrasound, the soluble and hydrophobic protein contents, free sulfhydryl content and surface hydrophobicity of RP increased. And the peptide content and hydrophobic amino acid content of protein-hydrolysate after gastrointestinal simulated digestion showed higher value (p < 0.05). In conclusion, the multi-mode S-type ultrasound pretreatment is an effective way in preparation of ACE inhibitory peptide from RP.


Assuntos
Inibidores da Enzima Conversora de Angiotensina/metabolismo , Oryza/metabolismo , Peptídeos/metabolismo , Peptidil Dipeptidase A/metabolismo , Proteínas de Plantas/metabolismo , Inibidores da Enzima Conversora de Angiotensina/química , Interações Hidrofóbicas e Hidrofílicas , Peptídeos/química , Peptidil Dipeptidase A/química , Proteínas de Plantas/química , Ligação Proteica , Hidrolisados de Proteína/química , Sonicação , Propriedades de Superfície
18.
Adv Exp Med Biol ; 1207: 149-161, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32671744

RESUMO

Polyglutamine (polyQ) disease is a type of fatal neurodegenerative disease caused by an expansion of CAG repeats in a specific gene, resulting in a protein with an abnormal polyQ fragment. The age of onset and the degree of pathological deterioration are related to the length of the polyQ fragment. At least 9 kinds of polyglutamine diseases have been discovered, including Huntington disease (HD), dentatorubral pallidoluysian atrophy (DRPLA), spinobulbar muscular atrophy (SBMA) and six spinocerebellar ataxia (SCA) such as SCA1, 2, 3, 6, 7 and 17 subtypes (Table 9.1). Previous studies suggest that autophagy plays a major role in the quality control of disease proteins in polyQ diseases. In this chapter, we majorly focused on three representative polyQ diseases, including spinocerebellar Ataxia type 3 (SCA3), spinocerebellar ataxia type 7 (SCA7) and Huntington's disease (HD). The relationship of the ubiquitin-proteasome system and autophagy involved in disease protein accumulation were summarized.


Assuntos
Autofagia , Atrofia Bulboespinal Ligada ao X , Doença de Huntington , Epilepsias Mioclônicas Progressivas , Peptídeos/metabolismo , Ataxias Espinocerebelares , Humanos
19.
PLoS One ; 15(6): e0233745, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32542029

RESUMO

The susceptibility of newly expressed proteins to digestion by gastrointestinal proteases (e.g., pepsin) has long been regarded as one of the important endpoints in the weight-of-evidence (WOE) approach to assess the allergenic risk of genetically modified (GM) crops. The European Food Safety Authority (EFSA) has suggested that current digestion study protocols used for this assessment should be modified to more accurately reflect the diverse physiological conditions encountered in human populations and that the post-digestion analysis should include analytical methods to detect small peptide digestion products.The susceptibility of two allergens (beta-lactoglobin (ß-Lg) and alpha-lactalbumin (α-La)) and two non-allergens (hemoglobin (Hb) and phosphofructokinase (PFK)) to proteolytic degradation was investigated under two pepsin digestion conditions (optimal pepsin digestion condition: pH 1.2, 10 U pepsin/µg test protein; sub-optimal pepsin digestion condition: pH 5.0, 1 U pepsin/10 mg test protein), followed by 34.5 U trypsin/mg test protein and 0.4 U chymotrypsin/mg test protein digestion in the absence or presence of bile salts. All samples were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in conjunction with Coomassie Blue staining and, in parallel, liquid chromatography tandem mass spectrometry (LC-MS) detection. The results provide following insights: 1) LC-MS methodology does provide the detection of small peptides; 2) Peptides are detected in both allergens and non-allergens from all digestion conditions; 3) No clear differences among the peptides detected from allergen and non-allergens; 4) The differences observed in SDS-PAGE between the optimal and sub-optimal pepsin digestion conditions are expected and align with kinetics and properties of the specific enzymes; 5) The new methodology with new digestion conditions and LC-MS detection does not provide any differentiating information for prediction whether a protein is an allergen. The classic pepsin resistance assay remains the most useful assessment of the potential exposure of an intact newly expressed protein as part of product safety assessment within a WOE approach.


Assuntos
Alérgenos/química , Análise de Alimentos/métodos , Peptídeos/química , Proteólise , Alérgenos/metabolismo , Animais , Cromatografia Líquida/métodos , Inocuidade dos Alimentos , Hemoglobinas/química , Hemoglobinas/metabolismo , Lactalbumina/química , Lactalbumina/metabolismo , Lactoglobulinas/química , Lactoglobulinas/metabolismo , Peptídeos/metabolismo , Fosfofrutoquinases/química , Fosfofrutoquinases/metabolismo , Suínos , Espectrometria de Massas em Tandem/métodos , Tripsina/metabolismo
20.
Nat Commun ; 11(1): 2702, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32483132

RESUMO

WIPI proteins (WIPI1-4) are mammalian PROPPIN family phosphoinositide effectors essential for autophagosome biogenesis. In addition to phosphoinositides, WIPI proteins can recognize a linear WIPI-interacting-region (WIR)-motif, but the underlying mechanism is poorly understood. Here, we determine the structure of WIPI3 in complex with the WIR-peptide from ATG2A. Unexpectedly, the WIR-peptide entwines around the WIPI3 seven-bladed ß-propeller and binds to three sites in blades 1-3. The N-terminal part of the WIR-peptide forms a short strand that augments the periphery of blade 2, the middle segment anchors into an inter-blade hydrophobic pocket between blades 2-3, and the C-terminal aromatic tail wedges into another tailored pocket between blades 1-2. Mutations in three peptide-binding sites disrupt the interactions between WIPI3/4 and ATG2A and impair the ATG2A-mediated autophagic process. Thus, WIPI proteins recognize the WIR-motif by multi-sites in multi-blades and this multi-site-mediated peptide-recognition mechanism could be applicable to other PROPPIN proteins.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Motivos de Aminoácidos/genética , Proteínas Relacionadas à Autofagia/genética , Autofagia/genética , Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Sequência de Aminoácidos , Animais , Proteínas Relacionadas à Autofagia/química , Proteínas Relacionadas à Autofagia/metabolismo , Sítios de Ligação/genética , Linhagem Celular , Cristalografia por Raios X , Células HEK293 , Humanos , Complexos Multiproteicos/química , Complexos Multiproteicos/metabolismo , Mutação , Peptídeos/química , Peptídeos/genética , Peptídeos/metabolismo , Ligação Proteica , Conformação Proteica , Homologia de Sequência de Aminoácidos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA