RESUMEN
Liquid-liquid phase separation (LLPS) of proteins into concentrated microdroplets (also called coacervation) is a phenomenon that is increasingly recognized to occur in many biological processes, both inside and outside the cell. While it has been established that LLPS can be described as a spinodal decomposition leading to demixing of an initially homogeneous protein solution, little is known about the assembly pathways by which soluble proteins aggregate into dense microdroplets. Using recent developments in techniques enabling the observation of matter suspended in liquid by transmission electron microscopy, we observed how a model intrinsically disordered protein phase-separates in liquid environment. Our observations reveal the dynamic mechanisms by which soluble proteins self-organize into condensed microdroplets with nanoscale and millisecond space and time resolution, respectively. With this method, the nucleation and initial growth steps of LLPS could be captured, opening the door for a deeper understanding of biomacromolecular complexes exhibiting LLPS ability.
Asunto(s)
Proteínas Intrínsecamente Desordenadas/química , Nanoestructuras/química , Transición de Fase , Animales , Fenómenos Bioquímicos , Decapodiformes/química , Microscopía Electrónica de Transmisión/métodos , Multimerización de ProteínaRESUMEN
The beak of the Humboldt squid is a biocomposite material made solely of organic components - chitin and proteins - which exhibits 200-fold stiffness and hardness gradients from the soft base to the exceptionally hard tip (rostrum). The outstanding mechanical properties of the squid beak are achieved via controlled hydration and impregnation of the chitin-based scaffold by protein coacervates. Molecular-based understanding of these proteins is essential to mimic the natural beak material. Here, we present detailed studies of two histidine-rich beak proteins (HBP-1 and -2) that play central roles during beak bio-fabrication. We show that both proteins have the ability to self-coacervate, which is governed intrinsically by the sequence modularity of their C-terminus and extrinsically by pH and ionic strength. We demonstrate that HBPs possess dynamic structures in solution and achieve maximum folding in the coacervate state, and propose that their self-coacervation is driven by hydrophobic interactions following charge neutralization through salt-screening. Finally, we show that subtle differences in the modular repeats of HBPs result in significant changes in the rheological response of the coacervates. This knowledge may be exploited to design self-coacervating polypeptides for a wide range of engineering and biomedical applications, for example bio-inspired composite materials, smart hydrogels and adhesives, and biomedical implants.
Asunto(s)
Pico/química , Decapodiformes/anatomía & histología , Proteínas/química , Animales , Quitina/química , Histidina/química , Conformación Proteica , ReologíaRESUMEN
The use of phage display to select material-specific peptides provides a general route towards modification and functionalization of surfaces and interfaces. However, a rational structural engineering of the peptides for optimal affinity is typically not feasible because of insufficient structure-function understanding. Here, we investigate the influence of multivalency of diamond-like carbon (DLC) binding peptides on binding characteristics. We show that facile linking of peptides together using different lengths of spacers and multivalency leads to a tuning of affinity and kinetics. Notably, increased length of spacers in divalent systems led to significantly increased affinities. Making multimers influenced also kinetic aspects of surface competition. Additionally, the multivalent peptides were applied as surface functionalization components for a colloidal form of DLC. The work suggests the use of a set of linking systems to screen parameters for functional optimization of selected material-specific peptides.
Asunto(s)
Carbono/química , Ingeniería Química/métodos , Diamante/química , Fragmentos de Péptidos/química , Carbono/metabolismo , Diamante/metabolismo , Fragmentos de Péptidos/metabolismo , Unión Proteica/fisiología , Propiedades de SuperficieRESUMEN
The molecular structural basis for the function of specific peptides that bind to diamond-like carbon (DLC) surfaces was investigated. For this, a competition assay that provided a robust way of comparing relative affinities of peptide variants was set up. Point mutations of specific residues resulted in significant effects, but it was shown that the chemical composition of the peptide was not sufficient to explain peptide affinity. More significantly, rearrangements in the sequence indicated that the binding is a complex recognition event that is dependent on the overall structure of the peptide. The work demonstrates the unique properties of peptides for creating functionality at interfaces via noncovalent binding for potential applications in, for example, nanomaterials, biomedical materials, and sensors.
Asunto(s)
Diamante/química , Péptidos/química , Proteínas Recombinantes de Fusión/química , Fosfatasa Alcalina/química , Fosfatasa Alcalina/genética , Secuencia de Aminoácidos , Unión Competitiva , Escherichia coli/genética , Escherichia coli/metabolismo , Expresión Génica , Genes Reporteros , Concentración de Iones de Hidrógeno , Cinética , Ensayo de Materiales , Datos de Secuencia Molecular , Péptidos/genética , Mutación Puntual , Unión Proteica , Proteínas Recombinantes de Fusión/genética , Relación Estructura-Actividad , Propiedades de SuperficieRESUMEN
Structural engineering of molecules for condensation is an emerging technique within synthetic biology. Liquid-liquid phase separation of biomolecules leading to condensation is a central step in the assembly of biological materials into their functional forms. Intracellular condensates can also function within cells in a regulatory manner to facilitate reaction pathways and to compartmentalize interactions. We need to develop a strong understanding of how to design molecules for condensates and how their in vivo-in vitro properties are related. The spider silk protein NT2RepCT undergoes condensation during its fiber-forming process. Using parallel in vivo and in vitro characterization, in this study, we mapped the effects of intracellular conditions for NT2RepCT and its several structural variants. We found that intracellular conditions may suppress to some extent condensation whereas molecular crowding affects both condensate properties and their formation. Intracellular characterization of protein condensation allowed experiments on pH effects and solubilization to be performed within yeast cells. The growth of intracellular NT2RepCT condensates was restricted, and Ostwald ripening was not observed in yeast cells, in contrast to earlier observations in E. coli. Our results lead the way to using intracellular condensation to screen for properties of molecular assembly. For characterizing different structural variants, intracellular functional characterization can eliminate the need for time-consuming batch purification and in vitro condensation. Therefore, we suggest that the in vivo-in vitro understanding will become useful in, e.g., high-throughput screening for molecular functions and in strategies for designing tunable intracellular condensates.
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Escherichia coli , Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Escherichia coli/genética , SedaRESUMEN
Chronic wounds are non-healing wounds characterized by a prolonged inflammation phase. Excessive inflammation leads to elevated protease levels and consequently to a decrease in growth factors at wound sites. Stem cell secretome therapy has been identified as a treatment strategy to modulate the microenvironment of chronic wounds via supplementation with anti-inflammatory/growth factors. However, there is a need to develop better secretome delivery systems that are able to encapsulate the secretome without denaturation, in a sustained manner, and that are fully biocompatible. To address this gap, a recombinant squid suckerin-spider silk fusion protein is developed with cell-adhesion motifs capable of thermal gelation at physiological temperatures to form hydrogels for encapsulation and subsequent release of the stem cell secretome. Freeze-thaw treatment of the protein hydrogel results in a modified porous cryogel that maintains slow degradation and sustained secretome release. Chronic wounds of diabetic mice treated with the secretome-laden cryogel display increased wound closure, presence of endothelial cells, granulation wound tissue thickness, and reduced inflammation with no fibrotic scar formation. Overall, these in vivo indicators of wound healing demonstrate that the fusion protein hydrogel displays remarkable potential as a delivery system for secretome-assisted chronic wound healing.
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Diabetes Mellitus Experimental , Células Madre Mesenquimatosas , Ratones , Animales , Humanos , Hidrogeles/farmacología , Criogeles , Seda , Secretoma , Células Endoteliales de la Vena Umbilical HumanaRESUMEN
Recombinant expression of proteins destined to form biological materials often results in poor production yields or loss of their function due to premature aggregation. Recently, liquid-liquid phase separation has been proposed as a mechanism to control protein solubility during expression and accumulation in the cytoplasm. Here, we investigate this process in vivo during the recombinant overexpression of the mimetic spider silk mini-spidroin NT2RepCT in Escherichia coli. The protein forms intracellular liquid-like condensates that shift to a solid-like state triggered by a decrease in their microenvironmental pH. These features are also maintained in the purified sample in vitro both in the presence of a molecular crowding agent mimicking the bacterial intracellular environment, and during a biomimetic extrusion process leading to fiber formation. Overall, we demonstrate that characterization of protein condensates inside E. coli could be used as a basis for selecting proteins for both materials applications and their fundamental structure-function studies.
RESUMEN
Studying pathogenic effects of amyloids requires homogeneous amyloidogenic peptide samples. Recombinant production of these peptides is challenging due to their susceptibility to aggregation and chemical modifications. Thus, chemical synthesis is primarily used to produce amyloidogenic peptides suitable for high-resolution structural studies. Here, we exploited the shielded environment of protein condensates formed via liquid-liquid phase separation (LLPS) as a protective mechanism against premature aggregation. We designed a fusion protein tag undergoing LLPS in Escherichia coli and linked it to highly amyloidogenic peptides, including ß amyloids. We find that the fusion proteins form membraneless organelles during overexpression and remain fluidic-like. We also developed a facile purification method of functional Aß peptides free of chromatography steps. The strategy exploiting LLPS can be applied to other amyloidogenic, hydrophobic, and repetitive peptides that are otherwise difficult to produce.
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Amiloide , Escherichia coli , Péptidos beta-Amiloides/genética , Escherichia coli/genética , Proteínas RecombinantesRESUMEN
Herein, we report on the precise design of a modular fusion protein amenable to the construction of nanocapsules by nanoprecipitation. The central squid suckerin-derived peptide block provides structural stability, whereas both termini from spider silk fibroins make the protein highly soluble at physiological pH, a critical requirement for the nanoprecipitation process. With this design, nanocapsules consisting of fusion protein shells and oily cores with sizes in the range of 190-250 nm are built in a straightforward manner.
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Fibroínas , Nanocápsulas , Animales , Decapodiformes/química , Fibroínas/química , Péptidos , Seda/químicaRESUMEN
Liquid-liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs) is involved in both intracellular membraneless organelles and extracellular tissues. Despite growing understanding of LLPS, molecular-level mechanisms behind this process are still not fully established. Here, we use histidine-rich squid beak proteins (HBPs) as model IDPs to shed light on molecular interactions governing LLPS. We show that LLPS of HBPs is mediated though specific modular repeats. The morphology of separated phases (liquid-like versus hydrogels) correlates with the repeats' hydrophobicity. Solution-state NMR indicates that LLPS is a multistep process initiated by deprotonation of histidine residues, followed by transient hydrogen bonding with tyrosine, and eventually by hydrophobic interactions. The microdroplets are stabilized by aromatic clustering of tyrosine residues exhibiting restricted molecular mobility in the nano-to-microsecond timescale according to solid-state NMR experiments. Our findings provide guidelines to rationally design pH-responsive peptides with LLPS ability for various applications, including bioinspired protocells and smart drug-delivery systems.
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Pico/metabolismo , Decapodiformes/metabolismo , Histidina/metabolismo , Proteínas Intrínsecamente Desordenadas/metabolismo , Tirosina/metabolismo , Animales , Pico/química , Materiales Biocompatibles , Biopolímeros/química , Biopolímeros/metabolismo , Coloides/química , Coloides/metabolismo , Enlace de Hidrógeno , Concentración de Iones de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Proteínas Intrínsecamente Desordenadas/química , Espectroscopía de Resonancia Magnética , Microscopía , Ingeniería de Proteínas/métodos , Dispersión del Ángulo PequeñoRESUMEN
Phage display was used to find peptides specific for amorphous diamond-like carbon (DLC). A set of putative binders was analyzed in detail and one sequence was found that functioned both as a peptide fused to the pIII protein in M13 phage and as a peptide fused to the enzyme alkaline phosphatase (AP). The dissociation constant of the peptide-AP fusion on DLC was 63nM and the maximum binding capacity was 6.8pmol/cm(2). Multiple ways of analysis, including phage titer, enzyme-linked immunosorbent assay, and ellipsometry were used to analyze binding and to exclude possible false positive results. DLC binding peptides can be useful for self-assembling coatings for modifying DLC in specific ways.
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Carbono/química , Péptidos/química , Fosfatasa Alcalina/química , Fosfatasa Alcalina/metabolismo , Sitios de Unión , Tamaño de la Partícula , Propiedades de SuperficieRESUMEN
INTRODUCTION: Growth disorders in children are multifactor, complex processes with often unknown etiology. The insulin-like growth factor-I (IGF-I) is one of the proteins participating in the transfer of growth signals, which are responsible in certain cases for the etiology of a growth disorder. AIM OF THE STUDY: The aim of the study was an analysis of the coding sequence of the extracellular and intracellular domains of IGF-IR responsible for ligand binding (IGF-I) and kinase activity in the DNA of children with growth disorders, who have normal or slightly decreased levels of plasma IGF-I. MATERIAL AND METHODS: DNA isolated from the peripheral blood of 50 short-statured children was used as study material. DNA fragments of IGF-IR obtained as a result of PCR amplification were analyzed using single stranded conformation polymorphism (SSCP) and sequencing. RESULTS: We did not observe any changes in the IGF-IR sequences, thus it can be excluded as a factor responsible for growth disorders. CONCLUSIONS: IGF-I receptor sequence changes are not the cause of growth disorders in the study group of children. To find the cause of growth disorders in the study group other proteins from somatotropic axis and/or signaling pathways should be studied in the future.
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Trastornos del Crecimiento/genética , Receptor IGF Tipo 1/química , Adolescente , Secuencia de Bases , Niño , Femenino , Perfilación de la Expresión Génica , Humanos , Masculino , Datos de Secuencia Molecular , Análisis de Secuencia por Matrices de Oligonucleótidos , Sistemas de Lectura AbiertaRESUMEN
Growth deficiency is one of the most frequent causes of referral to Endocrinology Outpatient Clinic. IGF-1 (insulin-like growth factor 1) deficiency is one of the rarest causes of short stature. In 2009 in Poland a therapeutic programme was set up for children with severe primary IGF-1 deficiency. The authors present the data of three first polish patients qualified for the rhIGF-1 (recombinant human insulin-like growth factor 1) - mecasermin. The authors conclude that the treatment with rhIGF-1 significantly improves growth velocity in patients with IGF-1 deficiency. During two years of mecasermin treatment no serious side effects were noted.