RESUMEN
This work illustrates a new role for the membranotropic peptide gH625 and its derivative gH625-GCGKKK in impairing formation of polymicrobial biofilms. Mixed biofilms composed of Candida and bacterial species cause frequently infections and failure of medical silicone devices and also show a major drug resistance than single-species biofilms. Inhibition and eradication of biofilms were evaluated by complementary methods: XTT-reduction, and crystal violet staining (CV). Our results indicate that gH625-GCGKKKK, better than the native peptide, strongly inhibited formation of mixed biofilms of clinical isolates of C. tropicalis/S. marcescens and C. tropicalis/S. aureus and reduced the biofilm architecture, interfering with cell adhesion and polymeric matrix, as well as eradicated the long-term polymicrobial biofilms on silicone surface.
Asunto(s)
Antiinfecciosos/metabolismo , Biopelículas/efectos de los fármacos , Candida tropicalis/efectos de los fármacos , Péptidos/metabolismo , Serratia marcescens/efectos de los fármacos , Staphylococcus aureus/efectos de los fármacos , Proteínas del Envoltorio Viral/metabolismo , Candida tropicalis/crecimiento & desarrollo , Formazáns/análisis , Violeta de Genciana/análisis , Serratia marcescens/crecimiento & desarrollo , Coloración y Etiquetado , Staphylococcus aureus/crecimiento & desarrolloRESUMEN
A versatile synthetic route based on magnetic Fe3O4 nanoparticle (MNP) prefunctionalization with a phosphonic acid monolayer has been used to covalently bind the gH625 peptide on the nanoparticle surface. gH625 is a membranotropic peptide capable of easily crossing the membranes of various cells including the typical human blood-brain barrier components. A similar synthetic route was used to prepare another class of MNPs having a functional coating based on PEG, rhodamine, and folic acid, a well-known target molecule, to compare the performance of the two cell-penetrating systems (i.e., gH625 and folic acid). Our results demonstrate that the uptake of gH625-decorated MNPs in immortalized human brain microvascular endothelial cells after 24 h is more evident compared to folic acid-functionalized MNPs as evidenced by confocal laser scanning microscopy. On the other hand, both functionalized systems proved capable of being internalized in a brain tumor cell line (i.e., glioblastoma A-172). These findings indicate that the functionalization of MNPs with gH625 improves their endothelial cell internalization, suggesting a viable strategy in designing functional nanostructures capable of first crossing the BBB and, then, of reaching specific tumor brain cells.
RESUMEN
The membranotropic peptide gH625 is able to transport different cargos (i.e., liposomes, quantum dots, polymeric nanoparticles) within and across cells in a very efficient manner. However, a clear understanding of the detailed uptake mechanism remains elusive. In this work, we investigate the journey of gH625-functionalized polystyrene nanoparticles in mouse-brain endothelial cells from their interaction with the cell membrane to their intracellular final destination. The aim is to elucidate how gH625 affects the behavior of the nanoparticles and their cytotoxic effect. The results indicate that the mechanism of translocation of gH625 dictates the fate of the nanoparticles, with a relevant impact on the nanotoxicological profile of positively charged nanoparticles.
Asunto(s)
Membrana Celular/metabolismo , Endosomas/metabolismo , Células Endoteliales/metabolismo , Lisosomas/metabolismo , Nanopartículas/toxicidad , Péptidos/farmacocinética , Proteínas del Envoltorio Viral/farmacocinética , Animales , Línea Celular , Corteza Cerebral/citología , Corteza Cerebral/metabolismo , Células Endoteliales/citología , Ratones , Nanopartículas/metabolismo , Péptidos/toxicidad , Propiedades de Superficie , Proteínas del Envoltorio Viral/toxicidadRESUMEN
The Antennapedia homeodomain structure consists of four helices. The helices II and III are connected by a tripeptide that forms a turn, and constitute the well-known helix-turn-helix motif. The recognition helix penetrates the DNA major groove, gives specific protein-DNA contacts and forms direct, or water-mediated, intermolecular hydrogen bonds. It was suggested that helix III (and perhaps also helix IV) might represent the recognition helix of Antennapedia homeodomain, which makes contact with the surface of the major groove of the DNA. In an attempt to clarify the helix III capabilities of assuming an helical conformation when separated from the rest of the protein, we carried out the structural determination of the recognition helix III in different solvent media. The conformational study of fragments 42-53, where residues W48 and F49, not involved in the protein-DNA interaction, were substituted by two alanines, was conducted in sodium dodecyl sulfate (SDS), trifluoroethanol (TFE) and TFE/water, using circular dichroism, nuclear magnetic resonance (NMR) and distance geometry (DG) techniques. The fragment assumes a well-defined secondary structure in TFE and in TFE/water (90/10, v/v) with an alpha-helix encompassing residues 4-9, while in TFE/water (70/30, v/v) a less regular structure was found. The DG results in the micellar system evidence the presence of a distorted alpha-helical conformation involving residues 4-8. Our results reveal that the isolated Antennapedia recognition helix III tend to preserve in solution the alpha-helical conformation even if separated from the rest of the molecule.
Asunto(s)
Proteínas de Homeodominio/química , Proteínas Nucleares/química , Péptidos/química , Factores de Transcripción/química , Animales , Proteína con Homeodominio Antennapedia , Espectroscopía de Resonancia Magnética , Estructura Secundaria de Proteína , Solventes/química , Trifluoroetanol/químicaRESUMEN
EST2 is a novel thermophilic carboxylesterase, isolated and cloned from Alicyclobacillus (formerly Bacillus) acidocaldarius, which optimally hydrolyses esters with acyl chain lengths of six to eight carbon atoms at 70 degrees C. On the basis of the amino acid sequence homology, it has been classified as a member of the mammalian hormone-sensitive lipase (HSL) subfamily. The crystal structure of EST2, complexed with a sulphonyl derivative, has been determined at 2.6 A resolution by a multiple wavelength anomalous diffraction experiment on a seleno-methionine derivative. EST2 presents a canonical alpha/beta hydrolase core, shielded at the C-terminal side by a cap region built up of five helices. It contains the lipase-like catalytic triad, Ser155, His282 and Asp252, whereby the nucleophile is covalently modified. This allows an unambiguous view of the putative active site of EST2, detecting the oxyanion hole, in whose formation the amino acid sequence motif His81-Gly82-Gly83-Gly84 is involved, and the hydrophobic binding pocket for the acyl chain. The structural model here reported provides the first example of a transition state analogue of an esterase/lipase belonging to the HSL group, thus affording useful information for the design of medical inhibitors. Moreover, as the first X-ray structure of a thermophilic carboxylesterase, the comparison with its mesophilic homologue, the Brefeldin A esterase (BFAE) from Bacillus subtilis, allows the identification of putative determinants of thermal stability.
Asunto(s)
Bacillus/enzimología , Hidrolasas de Éster Carboxílico/química , Hidrolasas de Éster Carboxílico/metabolismo , Esterol Esterasa/química , Secuencia de Aminoácidos , Sitios de Unión , Cristalografía por Rayos X , Estabilidad de Enzimas , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , Alineación de Secuencia , Esterol Esterasa/metabolismo , TemperaturaRESUMEN
A systematic structural analysis of Afc (9-amino-fluorene-9-carboxylic acid) containing peptides is here reported. The crystal structures of four fully protected tripeptides containing the Afc residue in position 2: Z-X(1)-Afc(2)-Y(3)-OMe (peptide a: X = Y = Gly; peptide b: X = Aib, C(alpha, alpha)-dimethylglycine, Y = Gly; peptide c: X = Gly, Y = Aib; peptide d: X = Y = Aib) have been solved by x-ray crystallography. All the results suggest that the Afc residue has a high propensity to assume an extended conformation. In fact, the Afc residue adopts an extended conformation in three peptides examined in this paper (peptides a-c). In contrast, Afc was found in a folded conformation, in the 3(10)-helical region, only in the peptide d, in which it is both preceded and followed by the strong helix promoting Aib.
Asunto(s)
Aminoácidos/química , Fluorenos/química , Oligopéptidos/química , Cristalografía por Rayos X , Glicina/química , Modelos Moleculares , Resonancia Magnética Nuclear Biomolecular , Oligopéptidos/síntesis química , Conformación ProteicaRESUMEN
We have investigated the conformational preferences of a newly synthesized C(alpha,alpha) symmetrically disubstituted glycine, namely alpha,alpha-dicyclopropylglycine (Dcp). We report here the crystal structure of a fully protected dipeptide containing Dcp, namely Z-Dcp(1)-Dcp(2)-OCH(3). Both Dcp residues are in a folded conformation. The overall peptide structural organization corresponds to an alpha-pleated sheet conformation, similar to that observed in linear peptides made up of alternating D- and L-residues and in Z-Aib-Aib-OCH(3) (Aib: alpha,alpha-dimethylglycine). These preliminary data suggest that the Dcp could represent an alternative as molecular tool to stabilize folded conformations.
Asunto(s)
Dipéptidos/química , Glicina/análogos & derivados , Cristalografía por Rayos X , Glicina/síntesis química , Glicina/química , Modelos Moleculares , Conformación ProteicaRESUMEN
EST2, a thermophilic carboxylesterase from Alicyclobacillus acidocaldarius, belonging to the HSL group of the esterase/lipase superfamily, has been crystallized for the first time. Ammonium sulfate was used as a precipitant and the crystallization proceeded at pH 7.8. The crystals belong to space group P41212 or its enantiomorph P43212, with unit-cell parameters a = b = 78.8, c = 106. 4 A. A complete data set has been collected at the synchrotron source Elettra in Trieste to 2.4 A resolution, using a single frozen crystal.
Asunto(s)
Bacillaceae/enzimología , Hidrolasas de Éster Carboxílico/química , Cristalización , Cristalografía por Rayos X , Conformación ProteicaRESUMEN
A large number of potent and selective therapeutic agents, useful for the treatment of several diseases, have been isolated from natural sources. For example, the most active thrombin inhibitors are those secreted by the salivary glands of leeches. One peculiar feature of these agents is the lack of any significant inhibitory cross-reaction with other serine proteinases. Hence, the knowledge of the exact mechanism of action of these molecules provides the basis for the development of new and efficient synthetic drugs. For this reason, many studies have been undertaken on the structure-activity relationships of natural thrombin inhibitors, and a large amount of detailed information has been obtained by the crystal structures of these inhibitors when complexed with thrombin. In this paper, we review natural and synthetic multisite thrombin inhibitors, whose structural aspects have been determined in detail. We also report here the approach used by us to develop a new class of synthetic, multisite directed thrombin inhibitors, named hirunorms, designed to mimic the distinctive binding mode of hirudin.
Asunto(s)
Antitrombinas/química , Inhibidores de Serina Proteinasa/química , Inhibidores de Serina Proteinasa/síntesis química , Trombina/antagonistas & inhibidores , Trombina/química , Secuencia de Aminoácidos , Animales , Antitrombinas/farmacología , Sitios de Unión , Diseño de Fármacos , Fibrinógeno/química , Fibrinógeno/metabolismo , Hirudinas/química , Hirudinas/aislamiento & purificación , Hirudinas/farmacología , Humanos , Sanguijuelas , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica , Inhibidores de Serina Proteinasa/farmacologíaRESUMEN
The X-ray crystal structure of the human alpha-thrombin-hirunorm IV complex has been determined at 2.5 A resolution, and refined to an R-factor of 0.173. The structure reveals an inhibitor binding mode distinctive of a true hirudin mimetic, which justifies the high inhibitory potency and the selectivity of hirunorm IV. This novel inhibitor, composed of 26 amino acids, interacts through the N-terminal end with the alpha-thrombin active site in a nonsubstrate mode, and binds specifically to the fibrinogen recognition exosite through the C-terminal end. The backbone of the N-terminal tripeptide Chg1"-Arg2"-2Na13" (Chg, cyclohexyl-glycine; 2Na1, beta-(2-naphthyl)-alanine) forms a parallel beta-strand to the thrombin main-chain segment Ser214-Gly216. The Chg1" side chain occupies the S2 site, Arg2" penetrates into the S1 specificity site, while the 2Na13" side chain occupies the aryl binding site. The Arg2" side chain enters the S1 specificity pocket from a position quite apart from the canonical P1 site. This notwithstanding, the Arg2" side chain establishes the typical ion pair with the carboxylate group of Asp189.
Asunto(s)
Péptidos/química , Trombina/química , Secuencia de Aminoácidos , Cristalografía por Rayos X , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica , Especificidad por SustratoRESUMEN
The central role of the serine protease thrombin in hemostasis and thrombosis brought many scientists to develop highly potent and selective thrombin inhibitors. Thrombin-inhibitor complexes have extensively been studied in order to understand structure-function relationships, and to design new inhibitors that can be used with broader efficacy over existing antithrombotic agents. In this paper, we summarize in a comparative manner the state of the art on reversible thrombin inhibitors and we discuss some structural aspects of thrombin-inhibitor interaction, which account for the different affinity and potency of these molecules. We also report here our approach to develop a new class of synthetic, multisite-directed thrombin inhibitors, named hirunorms, designed to mimic the distinctive binding mode of hirudin. We emphasize here that, despite the high specificity of thrombin action, the interaction of inhibitors in its active site may occur with quite different mechanisms.
Asunto(s)
Antitrombinas/metabolismo , Trombina/metabolismo , Clorometilcetonas de Aminoácidos/química , Clorometilcetonas de Aminoácidos/metabolismo , Animales , Antitrombinas/síntesis química , Antitrombinas/química , Sitios de Unión , Hirudinas/química , Hirudinas/metabolismo , Humanos , Imitación Molecular , Unión Proteica , Conformación ProteicaRESUMEN
A novel class of synthetic, multisite-directed thrombin inhibitors, known as hirunorms, has been described recently. These compounds were designed to mimic the binding mode of hirudin, and they have been proven to be very strong and selective thrombin inhibitors. Here we report the crystal structure of the complex formed by human alpha-thrombin and hirunorm V, a 26-residue polypeptide containing non-natural amino acids, determined at 2.1 A resolution and refined to an R-factor of 0.176. The structure reveals that the inhibitor binding mode is distinctive of a true hirudin mimetic, and it highlights the molecular basis of the high inhibitory potency (Ki is in the picomolar range) and the strong selectivity of hirunorm V. Hirunorm V interacts through the N-terminal tetrapeptide with the thrombin active site in a nonsubstrate mode; at the same time, this inhibitor specifically binds through the C-terminal segment to the fibrinogen recognition exosite. The backbone of the N-terminal tetrapeptide Chg1"-Val2"-2-Nal3"-Thr4" (Chg, cyclohexyl-glycine; 2-Nal, beta-(2-naphthyl)-alanine) forms a short beta-strand parallel to thrombin main-chain residues Ser214-Gly219. The Chg1" side chain fills the S2 subsite, Val2" is located at the entrance of S1, whereas 2-Nal3" side chain occupies the aryl-binding site. Such backbone orientation is very close to that observed for the N-terminal residues of hirudin, and it is similar to that of the synthetic retro-binding peptide BMS-183507, but it is opposite to the proposed binding mode of fibrinogen and of small synthetic substrates. Hirunorm V C-terminal segment binds to the fibrinogen recognition exosite, similarly to what observed for hirudin C-termninal tail and related compounds. The linker polypeptide segment connecting hirunorm V N-and C-terminal regions is not observable in the electron density maps. The crystallographic analysis proves the correctness of the design and it provides a compelling proof on the interaction mechanism for this novel class of high potency multisite-directed synthetic thrombin inhibitors.
Asunto(s)
Hirudinas/química , Imitación Molecular , Péptidos/química , Trombina/química , Antitrombinas/química , Cristalografía por Rayos X , Humanos , Oligopéptidos/química , Conformación Proteica , SolventesRESUMEN
A series of N- and C-protected, monodispersed homo-oligopeptides (to the pentamer level) from the cycloaliphatic C alpha,alpha-dialkylated glycine 1-aminocyclononane-1-carboxylic acid (Ac9c) and two Ala/Ac9c tripeptides have been synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives mCIAc-Ac9c-OH and Z-Ac9c-OtBu, the dipeptide pBrBz-(Ac9c)2-OtBu, the tetrapeptide Z-(Ac9c)4-OtBu, and the pentapeptide Z-(Ac9c)5-OtBu were determined in the crystal state by X-ray diffraction. Based on this information, the average geometry and the preferred conformation for the cyclononyl moiety of the Ac9c residue have been assessed. The backbone conformational data are strongly in favour of the conclusion that the Ac9c residue is a strong beta-turn and helix former. A comparison with the structural propensity of alpha-aminoisobutyric acid, the prototype of C alpha,alpha-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n = 3-8) is made and the implications for the use of the Ac9c residue in conformationally constrained analogues of bioactive peptides are briefly examined.
Asunto(s)
Aminoácidos Cíclicos/química , Oligopéptidos/química , Conformación Proteica , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos XRESUMEN
6I,6II-Diamino-6I,6II-dideoxy-cyclomaltoheptaose was prepared using the regioselective procedure described by Tabushi. The difunctionalized beta-cyclodextrin crystallizes as hexadecahydrate in the orthorhombic space group P2(1)2(1)2(1), with a = 11.395(3), b = 32.989(9), c = 17.560(5) A, V = 6601 A3, Z = 4. The structure was solved by molecular replacement techniques using the program PATSEE and was refined to a conventional final R = 0.058 for the 5031 observed reflections with I > or = 3 sigma(I). The beta-CD macrocycle presents only slight differences with respect to uncomplexed hydrated or methylated beta-CD. The macrocycle structure maintains an approximate seven-fold symmetry. The round shape of the cyclodextrin ring is stabilized by intramolecular O-H ... O H-bonds between the secondary hydroxyl groups of neighbouring glucose residues. Along the a axis, the beta-CD molecules are arranged in columns; the macrocycles form a herring-bone pattern, so that the cavity of each beta-CD molecule is closed at each end by neighbouring molecules. The macrocycles are directly linked to each other by H-bonds involving either primary and secondary hydroxyl or amino groups of symmetry-related molecules. The resulting layers are connected to each other by a dense intermolecular hydrogen-bond network, in which solvent molecules participate.
Asunto(s)
Ciclodextrinas/química , Ciclodextrinas/síntesis química , beta-Ciclodextrinas , Secuencia de Carbohidratos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Datos de Secuencia Molecular , Rotación Óptica , Espectrometría de Masa Bombardeada por Átomos Veloces , Difracción de Rayos XRESUMEN
The terminally blocked tetrapeptide pBrBz-[D-(alpha Me)Leu]2-D-(alpha Me)Val-D-(alpha Me)Leu-OfBu is folded in the crystal state in a left-handed 3(10)-helical structure stabilized by two consecutive 1<--4 C = O...H-N intramolecular H-bonds, as determined by X-ray diffraction analysis. A CD study strongly supports the view that this conformation is also that largely prevailing in MeOH solution. A comparison with the published conformation of pBrBz-[D-(alpha Me)Leu]4-OfBu indicates that incorporation of a single internal beta-branched (alpha Me)Val guest residue into the host homo-tetrapeptide from the gamma-branched (alpha Me)Leu residue is responsible for a dramatic structural perturbation, i.e. an inversion of the 3(10) screw sense from right to left-handed.
Asunto(s)
Oligopéptidos/química , Secuencia de Aminoácidos , Dicroismo Circular , Cristalografía por Rayos X , Enlace de Hidrógeno , Metilación , Modelos Moleculares , Estructura Molecular , Oligopéptidos/síntesis química , Pliegue de Proteína , Estructura Secundaria de ProteínaRESUMEN
A 34-year-old man experienced progressive muscle weakness and wasting in the shoulder girdle later spreading distally to the upper limbs. Neurological examination revealed signs of pyramidal and bulbar involvement as well as widespread fasciculations. Pes cavus and distal hypoesthesia were also observed. MCV and nerve biopsy findings were consistent with HMSN-I, while EMG pattern suggested a MND. The association of HMSN-I with MND has not been previously described in literature.
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Neuropatía Hereditaria Motora y Sensorial/complicaciones , Enfermedades Neuromusculares/complicaciones , Adulto , Biopsia , Neuropatía Hereditaria Motora y Sensorial/patología , Neuropatía Hereditaria Motora y Sensorial/fisiopatología , Humanos , Masculino , Conducción Nerviosa , Enfermedades Neuromusculares/patología , Enfermedades Neuromusculares/fisiopatologíaRESUMEN
The Authors present two cases of Wernicke-Korsakoff Disease following gastric surgery. This clinical occurrence hasn't been previously described in Literature. The pathogenetical role of nutritional factors deficiency is discussed.