Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 24
Filtrar
Más filtros












Base de datos
Intervalo de año de publicación
1.
J Fungi (Basel) ; 9(2)2023 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-36836270

RESUMEN

Earlier studies have shown that the outer layers of the conidial and mycelial cell walls of Aspergillus fumigatus are different. In this work, we analyzed the polysaccharidome of the resting conidial cell wall and observed major differences within the mycelium cell wall. Mainly, the conidia cell wall was characterized by (i) a smaller amount of α-(1,3)-glucan and chitin; (ii) a larger amount of ß-(1,3)-glucan, which was divided into alkali-insoluble and water-soluble fractions, and (iii) the existence of a specific mannan with side chains containing galactopyranose, glucose, and N-acetylglucosamine residues. An analysis of A. fumigatus cell wall gene mutants suggested that members of the fungal GH-72 transglycosylase family play a crucial role in the conidia cell wall ß-(1,3)-glucan organization and that α-(1,6)-mannosyltransferases of GT-32 and GT-62 families are essential to the polymerization of the conidium-associated cell wall mannan. This specific mannan and the well-known galactomannan follow two independent biosynthetic pathways.

2.
Front Immunol ; 12: 749074, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34867977

RESUMEN

In this study, the human immune response mechanisms against Sporothrix brasiliensis and Sporothrix schenckii, two causative agents of human and animal sporotrichosis, were investigated. The interaction of S. brasiliensis and S. schenckii with human monocyte-derived macrophages (hMDMs) was shown to be dependent on the thermolabile serum complement protein C3, which facilitated the phagocytosis of Sporothrix yeast cells through opsonization. The peptidorhamnomannan (PRM) component of the cell walls of these two Sporothrix yeasts was found to be one of their surfaces exposed pathogen-associated molecular pattern (PAMP), leading to activation of the complement system and deposition of C3b on the Sporothrix yeast surfaces. PRM also showed direct interaction with CD11b, the specific component of the complement receptor-3 (CR3). Furthermore, the blockade of CR3 specifically impacted the interleukin (IL)-1ß secretion by hMDM in response to both S. brasiliensis and S. schenckii, suggesting that the host complement system plays an essential role in the inflammatory immune response against these Sporothrix species. Nevertheless, the structural differences in the PRMs of the two Sporothrix species, as revealed by NMR, were related to the differences observed in the host complement activation pathways. Together, this work reports a new PAMP of the cell surface of pathogenic fungi playing a role through the activation of complement system and via CR3 receptor mediating an inflammatory response to Sporothrix species.


Asunto(s)
Antígenos Fúngicos/inmunología , Proteínas del Sistema Complemento/inmunología , Glicoproteínas/inmunología , Macrófagos/inmunología , Sporothrix , Pared Celular/inmunología , Activación de Complemento , Citocinas/inmunología , Humanos , L-Lactato Deshidrogenasa/inmunología , Antígeno de Macrófago-1/inmunología , Macrófagos/microbiología , Moléculas de Patrón Molecular Asociado a Patógenos/inmunología , Fagocitosis
3.
Sci Rep ; 9(1): 7438, 2019 05 15.
Artículo en Inglés | MEDLINE | ID: mdl-31092861

RESUMEN

The human protein tyrosine phosphatase non-receptor type 3 (PTPN3) is a PDZ (PSD-95/Dlg/ZO-1) domain-containing phosphatase with a tumor-suppressive or a tumor-promoting role in many cancers. Interestingly, the high-risk genital human papillomavirus (HPV) types 16 and 18 target the PDZ domain of PTPN3. The presence of a PDZ binding motif (PBM) on E6 confers interaction with a number of different cellular PDZ domain-containing proteins and is a marker of high oncogenic potential. Here, we report the molecular basis of interaction between the PDZ domain of PTPN3 and the PBM of the HPV E6 protein. We combined biophysical, NMR and X-ray experiments to investigate the structural and functional properties of the PDZ domain of PTPN3. We showed that the C-terminal sequences from viral proteins encompassing a PBM interact with PTPN3-PDZ with similar affinities to the endogenous PTPN3 ligand MAP kinase p38γ. PBM binding stabilizes the PDZ domain of PTPN3. We solved the X-ray structure of the PDZ domain of PTPN3 in complex with the PBM of the HPV E6 protein. The crystal structure and the NMR chemical shift mapping of the PTPN3-PDZ/peptide complex allowed us to pinpoint the main structural determinants of recognition of the C-terminal sequence of the E6 protein and the long-range perturbations induced upon PBM binding.


Asunto(s)
Proteínas de Unión al ADN/metabolismo , Papillomavirus Humano 16/metabolismo , Papillomavirus Humano 18/metabolismo , Proteínas Oncogénicas Virales/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 3/metabolismo , Proteínas Represoras/metabolismo , Secuencia de Aminoácidos , Cristalografía por Rayos X , Humanos , Ligandos , Proteína Quinasa 12 Activada por Mitógenos/metabolismo , Dominios PDZ , Infecciones por Papillomavirus/metabolismo , Monoéster Fosfórico Hidrolasas/metabolismo , Unión Proteica , Estabilidad Proteica , Proteína Tirosina Fosfatasa no Receptora Tipo 3/química , Proteína Tirosina Fosfatasa no Receptora Tipo 3/genética , Relación Estructura-Actividad
4.
Biochemistry ; 58(6): 526-533, 2019 02 12.
Artículo en Inglés | MEDLINE | ID: mdl-30521325

RESUMEN

Detailed information on hit-target interaction is very valuable for drug discovery efforts and indispensable for rational hit to lead optimization. We developed a new approach combining NMR in whole-cells in-cell NMR) and docking to characterize hit-target interaction at the atomic level. By using in-cell NMR, we validated target engagement of the antituberculosis imidazopyridine amide (IPA) series with the subunit b of the cytochrome bc1:aa3, the major respiratory terminal oxidase in mycobacteria. The most advanced IPA called Q203 is currently in clinical trial. Using its derivative IPA317, we identified the atoms of the drug interacting with the cytochrome b in whole cells. NMR data and the self-organizing map algorithm were used to cluster a large set of drug-target complex models. The selected ensemble revealed IPA317 in a transient cavity of the cytochrome b, interacting directly with the residue T313, which is the site of spontaneous mutation conferring resistance to the IPA series. Our approach constitutes a pipeline to obtain atomic information on hit-target interactions in the cellular context.


Asunto(s)
Antituberculosos/farmacología , Citocromos b/metabolismo , Descubrimiento de Drogas , Espectroscopía de Resonancia Magnética/métodos , Mycobacterium tuberculosis/efectos de los fármacos , Mycobacterium tuberculosis/metabolismo , Antituberculosos/química , Humanos
5.
mBio ; 8(3)2017 06 20.
Artículo en Inglés | MEDLINE | ID: mdl-28634239

RESUMEN

ß-(1,3)-Glucan, the major fungal cell wall component, ramifies through ß-(1,6)-glycosidic linkages, which facilitates its binding with other cell wall components contributing to proper cell wall assembly. Using Saccharomyces cerevisiae as a model, we developed a protocol to quantify ß-(1,6)-branching on ß-(1,3)-glucan. Permeabilized S. cerevisiae and radiolabeled substrate UDP-(14C)glucose allowed us to determine branching kinetics. A screening aimed at identifying deletion mutants with reduced branching among them revealed only two, the bgl2Δ and gas1Δ mutants, showing 15% and 70% reductions in the branching, respectively, compared to the wild-type strain. Interestingly, a recombinant Gas1p introduced ß-(1,6)-branching on the ß-(1,3)-oligomers following its ß-(1,3)-elongase activity. Sequential elongation and branching activity of Gas1p occurred on linear ß-(1,3)-oligomers as well as Bgl2p-catalyzed products [short ß-(1,3)-oligomers linked by a linear ß-(1,6)-linkage]. The double S. cerevisiae gas1Δ bgl2Δ mutant showed a drastically sick phenotype. An ScGas1p ortholog, Gel4p from Aspergillus fumigatus, also showed dual ß-(1,3)-glucan elongating and branching activity. Both ScGas1p and A. fumigatus Gel4p sequences are endowed with a carbohydrate binding module (CBM), CBM43, which was required for the dual ß-(1,3)-glucan elongating and branching activity. Our report unravels the ß-(1,3)-glucan branching mechanism, a phenomenon occurring during construction of the cell wall which is essential for fungal life.IMPORTANCE The fungal cell wall is essential for growth, morphogenesis, protection, and survival. In spite of being essential, cell wall biogenesis, especially the core ß-(1,3)-glucan ramification, is poorly understood; the ramified ß-(1,3)-glucan interconnects other cell wall components. Once linear ß-(1,3)-glucan is synthesized by plasma membrane-bound glucan synthase, the subsequent event is its branching event in the cell wall space. Using Saccharomyces cerevisiae as a model, we identified GH72 and GH17 family glycosyltransferases, Gas1p and Bgl2p, respectively, involved in the ß-(1,3)-glucan branching. The sick phenotype of the double Scgas1Δ bgl2Δ mutant suggested that ß-(1,3)-glucan branching is essential. In addition to ScGas1p, GH72 family ScGas2p and Aspergillus fumigatus Gel4p, having CBM43 in their sequences, showed dual ß-(1,3)-glucan elongating and branching activity. Our report identifies the fungal cell wall ß-(1,3)-glucan branching mechanism. The essentiality of ß-(1,3)-glucan branching suggests that enzymes involved in the glucan branching could be exploited as antifungal targets.


Asunto(s)
Pared Celular/metabolismo , Glucano Endo-1,3-beta-D-Glucosidasa/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/enzimología , Saccharomyces cerevisiae/metabolismo , beta-Glucanos/metabolismo , Aspergillus fumigatus/enzimología , Aspergillus fumigatus/genética , Aspergillus fumigatus/metabolismo , Eliminación de Gen , Pruebas Genéticas , Glucano Endo-1,3-beta-D-Glucosidasa/genética , Glicoproteínas de Membrana/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética
6.
Org Biomol Chem ; 15(1): 114-123, 2016 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-27812586

RESUMEN

Herein, we report a new process that enables the gram-scale production of a fully synthetic anti-cancer vaccine for human use. This therapeutic vaccine candidate, named MAG-Tn3, is a high-molecular-weight tetrameric glycopeptide encompassing carbohydrate tumor-associated Tn antigen clusters and peptidic CD4+ T-cell epitopes. The synthetic process involves (i) the stepwise solid-phase assembly of protected amino acids, including the high value-added Tn building blocks with only 1.5 equivalents, (ii) a single isolated intermediate, and (iii) the simultaneous deprotection of 36 hindered protective groups. The resulting MAG-Tn3 was unambiguously characterized using a combination of techniques, including a structural analysis by nuclear magnetic resonance spectroscopy. The four peptidic chains are flexible in solution, with a more constrained but extended conformation at the Tn3 antigen motif. Finally, we demonstrate that, when injected into HLA-DR1-expressing transgenic mice, this vaccine induces Tn-specific antibodies that mediate the killing of human Tn-positive tumor cells. These studies led to a clinical batch of the MAG-Tn3, currently investigated in breast cancer patients (phase I clinical trial). The current study demonstrates the feasibility of the multigram-scale synthesis of a highly pure complex glycopeptide, and it opens new avenues for the use of synthetic glycopeptides as drugs in humans.


Asunto(s)
Vacunas contra el Cáncer/química , Dendrímeros/química , Glicopéptidos/química , Neoplasias/prevención & control , Vacunas Sintéticas/química , Secuencia de Aminoácidos , Animales , Antígenos de Carbohidratos Asociados a Tumores/química , Antígenos de Carbohidratos Asociados a Tumores/inmunología , Linfocitos T CD4-Positivos/inmunología , Vacunas contra el Cáncer/síntesis química , Vacunas contra el Cáncer/uso terapéutico , Dendrímeros/síntesis química , Dendrímeros/uso terapéutico , Glicopéptidos/síntesis química , Glicopéptidos/uso terapéutico , Humanos , Ratones , Ratones Transgénicos , Neoplasias/inmunología , Vacunas Sintéticas/uso terapéutico
7.
Biochem J ; 473(14): 2239-48, 2016 07 15.
Artículo en Inglés | MEDLINE | ID: mdl-27208170

RESUMEN

Bacteria use diverse signalling pathways to adapt gene expression to external stimuli. In Gram-negative bacteria, the binding of scarce nutrients to membrane transporters triggers a signalling process that up-regulates the expression of genes of various functions, from uptake of nutrient to production of virulence factors. Although proteins involved in this process have been identified, signal transduction through this family of transporters is not well understood. In the present study, using an integrative approach (EM, SAXS, X-ray crystallography and NMR), we have studied the structure of the haem transporter HasR captured in two stages of the signalling process, i.e. before and after the arrival of signalling activators (haem and its carrier protein). We show for the first time that the HasR domain responsible for signal transfer: (i) is highly flexible in two stages of signalling; (ii) extends into the periplasm at approximately 70-90 Å (1 Å=0.1 nm) from the HasR ß-barrel; and (iii) exhibits local conformational changes in response to the arrival of signalling activators. These features would favour the signal transfer from HasR to its cytoplasmic membrane partners.


Asunto(s)
Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Proteínas de Transporte de Membrana/química , Proteínas de Transporte de Membrana/metabolismo , Cristalografía por Rayos X , Hemo/metabolismo , Espectroscopía de Resonancia Magnética , Microscopía Electrónica , Unión Proteica , Serratia marcescens/metabolismo , Transducción de Señal/fisiología
8.
PLoS One ; 9(4): e89502, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24727671

RESUMEN

Bacteria use diverse signaling pathways to control gene expression in response to external stimuli. In Gram-negative bacteria, the binding of a nutrient is sensed by an outer membrane transporter. This signal is then transmitted to an antisigma factor and subsequently to the cytoplasm where an ECF sigma factor induces expression of genes related to the acquisition of this nutrient. The molecular interactions involved in this transmembrane signaling are poorly understood and structural data on this family of antisigma factor are rare. Here, we present the first structural study of the periplasmic domain of an antisigma factor and its interaction with the transporter. The study concerns the signaling in the heme acquisition system (Has) of Serratia marcescens. Our data support unprecedented partially disordered periplasmic domain of an anti-sigma factor HasS in contact with a membrane-mimicking environment. We solved the 3D structure of the signaling domain of HasR transporter and identified the residues at the HasS-HasR interface. Their conservation in several bacteria suggests wider significance of the proposed model for the understanding of bacterial transmembrane signaling.


Asunto(s)
Proteínas Bacterianas/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Serratia marcescens/metabolismo , Transducción de Señal/fisiología , Periplasma/metabolismo , Unión Proteica
9.
J Biol Chem ; 289(18): 12647-56, 2014 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-24627479

RESUMEN

Malassezia species are ubiquitous residents of human skin and are associated with several diseases such as seborrheic dermatitis, tinea versicolor, folliculitis, atopic dermatitis, and scalp conditions such as dandruff. Host-Malassezia interactions and mechanisms to evade local immune responses remain largely unknown. Malassezia restricta is one of the most predominant yeasts of the healthy human skin, its cell wall has been investigated in this paper. Polysaccharides in the M. restricta cell wall are almost exclusively alkali-insoluble, showing that they play an essential role in the organization and rigidity of the M. restricta cell wall. Fractionation of cell wall polymers and carbohydrate analyses showed that the polysaccharide core of the cell wall of M. restricta contained an average of 5% chitin, 20% chitosan, 5% ß-(1,3)-glucan, and 70% ß-(1,6)-glucan. In contrast to other yeasts, chitin and chitosan are relatively abundant, and ß-(1,3)-glucans constitute a minor cell wall component. The most abundant polymer is ß-(1,6)-glucans, which are large molecules composed of a linear ß-(1,6)-glucan chains with ß-(1,3)-glucosyl side chain with an average of 1 branch point every 3.8 glucose unit. Both ß-glucans are cross-linked, forming a huge alkali-insoluble complex with chitin and chitosan polymers. Data presented here show that M. restricta has a polysaccharide organization very different of all fungal species analyzed to date.


Asunto(s)
Pared Celular/química , Dermatomicosis/microbiología , Malassezia/química , Polisacáridos/análisis , Quitina/análisis , Quitina/química , Cromatografía Liquida , Humanos , Espectroscopía de Resonancia Magnética , Polisacáridos/química , Proteoglicanos , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , beta-Glucanos/análisis , beta-Glucanos/química
10.
PLoS One ; 8(3): e58964, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-23527057

RESUMEN

TonB is a key protein in active transport of essential nutrients like vitamin B12 and metal sources through the outer membrane transporters of Gram-negative bacteria. This inner membrane protein spans the periplasm, contacts the outer membrane receptor by its periplasmic domain and transduces energy from the cytoplasmic membrane pmf to the receptor allowing nutrient internalization. Whereas generally a single TonB protein allows the acquisition of several nutrients through their cognate receptor, in some species one particular TonB is dedicated to a specific system. Despite a considerable amount of data available, the molecular mechanism of TonB-dependent active transport is still poorly understood. In this work, we present a structural study of a TonB-like protein, HasB dedicated to the HasR receptor. HasR acquires heme either free or via an extracellular heme transporter, the hemophore HasA. Heme is used as an iron source by bacteria. We have solved the structure of the HasB periplasmic domain of Serratia marcescens and describe its interaction with a critical region of HasR. Some important differences are observed between HasB and TonB structures. The HasB fold reveals a new structural class of TonB-like proteins. Furthermore, we have identified the structural features that explain the functional specificity of HasB. These results give a new insight into the molecular mechanism of nutrient active transport through the bacterial outer membrane and present the first detailed structural study of a specific TonB-like protein and its interaction with the receptor.


Asunto(s)
Proteínas Bacterianas/química , Proteínas de la Membrana/química , Pliegue de Proteína , Secuencia de Aminoácidos , Aminoácidos , Proteínas Bacterianas/metabolismo , Sitios de Unión , Proteínas de la Membrana/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Péptidos/química , Péptidos/metabolismo , Unión Proteica , Conformación Proteica , Estructura Secundaria de Proteína , Alineación de Secuencia
11.
Biomol NMR Assign ; 7(1): 43-6, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-22415545

RESUMEN

TonB-dependent transporters (TBDTs) are bacterial outer membrane proteins that internalize nutrients such as vitamin B12, metal complexes, heme, some carbohydrates, etc. In addition to their transport activity, several TBDTs are also involved in a signalling cascade from the cell surface into the cytoplasm, via their periplasmic signalling domain. Here we report the backbone and side chain resonance assignments of the signalling domain of HasR, a TonB-dependent outer membrane heme transporter from Serratia marcescens as a first step towards its structural study.


Asunto(s)
Proteínas Bacterianas/química , Proteínas de Transporte de Membrana/química , Resonancia Magnética Nuclear Biomolecular , Periplasma/metabolismo , Proteínas Bacterianas/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Estructura Terciaria de Proteína , Serratia marcescens/citología
12.
Sci Signal ; 5(237): ra58, 2012 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-22894835

RESUMEN

PTEN (phosphatase and tensin homolog deleted on chromosome 10) and MAST2 (microtubule-associated serine and threonine kinase 2) interact with each other through the PDZ domain of MAST2 (MAST2-PDZ) and the carboxyl-terminal (C-terminal) PDZ domain-binding site (PDZ-BS) of PTEN. These two proteins function as negative regulators of cell survival pathways, and silencing of either one promotes neuronal survival. In human neuroblastoma cells infected with rabies virus (RABV), the C-terminal PDZ domain of the viral glycoprotein (G protein) can target MAST2-PDZ, and RABV infection triggers neuronal survival in a PDZ-BS-dependent fashion. These findings suggest that the PTEN-MAST2 complex inhibits neuronal survival and that viral G protein disrupts this complex through competition with PTEN for binding to MAST2-PDZ. We showed that the C-terminal sequences of PTEN and the viral G protein bound to MAST2-PDZ with similar affinities. Nuclear magnetic resonance structures of these complexes exhibited similar large interaction surfaces, providing a structural basis for their binding specificities. Additionally, the viral G protein promoted the nuclear exclusion of PTEN in infected neuroblastoma cells in a PDZ-BS-dependent manner without altering total PTEN abundance. These findings suggest that formation of the PTEN-MAST2 complex is specifically affected by the viral G protein and emphasize how disruption of a critical protein-protein interaction regulates intracellular PTEN trafficking. In turn, the data show how the viral protein might be used to decipher the underlying molecular mechanisms and to clarify how the subcellular localization of PTEN regulates neuronal survival.


Asunto(s)
Glicoproteínas/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Modelos Moleculares , Neuronas/fisiología , Fosfohidrolasa PTEN/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Virus de la Rabia/metabolismo , Proteínas Virales/metabolismo , Unión Competitiva , Western Blotting , Calorimetría , Línea Celular Tumoral , Supervivencia Celular/fisiología , Glicoproteínas/química , Humanos , Inmunohistoquímica , Marcaje Isotópico , Proteínas Asociadas a Microtúbulos/química , Neuronas/metabolismo , Resonancia Magnética Nuclear Biomolecular , Dominios PDZ/fisiología , Fosfohidrolasa PTEN/química , Proteínas Serina-Treonina Quinasas/química , Espectrometría de Fluorescencia , Proteínas Virales/química
13.
PLoS Pathog ; 7(11): e1002372, 2011 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-22102815

RESUMEN

A new polysaccharide secreted by the human opportunistic fungal pathogen Aspergillus fumigatus has been characterized. Carbohydrate analysis using specific chemical degradations, mass spectrometry, ¹H and ¹³C nuclear magnetic resonance showed that this polysaccharide is a linear heterogeneous galactosaminogalactan composed of α1-4 linked galactose and α1-4 linked N-acetylgalactosamine residues where both monosacharides are randomly distributed and where the percentage of galactose per chain varied from 15 to 60%. This polysaccharide is antigenic and is recognized by a majority of the human population irrespectively of the occurrence of an Aspergillus infection. GalNAc oligosaccharides are an essential epitope of the galactosaminogalactan that explains the universal antibody reaction due to cross reactivity with other antigenic molecules containing GalNAc stretches such as the N-glycans of Campylobacter jejuni. The galactosaminogalactan has no protective effect during Aspergillus infections. Most importantly, the polysaccharide promotes fungal development in immunocompetent mice due to its immunosuppressive activity associated with disminished neutrophil infiltrates.


Asunto(s)
Antígenos Fúngicos/inmunología , Aspergilosis/inmunología , Aspergillus fumigatus/inmunología , Inmunosupresores , Polisacáridos/química , Polisacáridos/inmunología , Animales , Anticuerpos Antifúngicos/inmunología , Apoptosis , Aspergillus fumigatus/metabolismo , Conformación de Carbohidratos , Secuencia de Carbohidratos , Pared Celular/inmunología , Reacciones Cruzadas , Epítopos , Femenino , Interacciones Huésped-Patógeno , Humanos , Macrófagos/inmunología , Espectroscopía de Resonancia Magnética , Ratones , Ratones Endogámicos C57BL , Infiltración Neutrófila , Neutrófilos/inmunología , Neutrófilos/fisiología , Polisacáridos/metabolismo , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción
14.
Glycobiology ; 21(12): 1570-9, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-21610193

RESUMEN

Carbohydrates are likely to maintain significant conformational flexibility in antibody (Ab):carbohydrate complexes. As demonstrated herein for the protective monoclonal Ab (mAb) F22-4 recognizing the Shigella flexneri 2a O-antigen (O-Ag) and numerous synthetic oligosaccharide fragments thereof, the combination of molecular dynamics simulations and nuclear magnetic resonance saturation transfer difference experiments, supported by physicochemical analysis, allows us to determine the binding epitope and its various contributions to affinity without using any modified oligosaccharides. Moreover, the methods used provide insights into ligand flexibility in the complex, thus enabling a better understanding of the Ab affinities observed for a representative set of synthetic O-Ag fragments. Additionally, these complementary pieces of information give evidence to the ability of the studied mAb to recognize internal as well as terminal epitopes of its cognate polysaccharide antigen. Hence, we show that an appropriate combination of computational and experimental methods provides a basis to explore carbohydrate functional mimicry and receptor binding. The strategy may facilitate the design of either ligands or carbohydrate recognition domains, according to needed improvements of the natural carbohydrate:receptor properties.


Asunto(s)
Anticuerpos Monoclonales/química , Simulación de Dinámica Molecular , Resonancia Magnética Nuclear Biomolecular , Oligosacáridos/química
15.
Glycobiology ; 21(1): 109-21, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-21030536

RESUMEN

The O-antigen (O-Ag), the polysaccharide part of the lipopolysaccharide, is the major target of the serotype-specific protective humoral response elicited upon host infection by Shigella flexneri, the main causal agent of the endemic form of bacillary dysentery. The O-Ag repeat units (RUs) of 12 S. flexneri serotypes share the tetrasaccharide backbone →2)-α-l-Rhap-(1 â†’ 2)-α-l-Rhap-(1 â†’ 3)-α-l-Rhap-(1 â†’ 3)-ß-d-GlcpNAc-(1→, with site-selective glucosylation(s) and/or O-acetylation defining the serotypes. To investigate the conformational basis of serotype specificity, we sampled conformational behaviors during 60 ns of molecular dynamic simulations for oligosaccharides representing three RUs of each one of the O-Ags corresponding to serotypes 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, X and Y, respectively. The calculated trajectories were checked by nuclear magnetic resonance (NMR) for 1a, 2a, 3a and 5a O-Ags. The simulations predict that in all O-Ags, but 1a and 1b, serotype-specific substitutions of the backbone do not induce any new backbone conformations compared with the linear type O-Ag Y, although they restrain locally the accessible conformational space. Moreover, the influence of any given substituent on the backbone is independent of the eventual presence of other substituents. Finally, only slight differences in conformational behavior between terminal and inner RUs were observed. These results suggest that the reported serotype-specificity of the protective immune response is not due to recognition of distinct backbone conformations, but to binding of the serotype-defining substituents in the O-Ag context. The gained knowledge is discussed in terms of impact on the development of a broad-serotype coverage vaccine.


Asunto(s)
Lipopolisacáridos/química , Antígenos O/química , Vacunas contra la Shigella/química , Shigella flexneri/inmunología , Sitios de Unión , Espectroscopía de Resonancia Magnética , Simulación de Dinámica Molecular , Datos de Secuencia Molecular , Antígenos O/inmunología , Vacunas contra la Shigella/inmunología
16.
J Biol Chem ; 285(4): 2386-96, 2010 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-19948732

RESUMEN

A new HPLC method was developed to separate linear from beta(1-6)-branched beta(1-3)-glucooligosaccharides. This methodology has permitted the isolation of the first fungal beta(1-6)/beta(1-3)-glucan branching transglycosidase using a cell wall autolysate of Aspergillus fumigatus (Af). The encoding gene, AfBGT2 is an ortholog of AfBGT1, another transglycosidase of A. fumigatus previously analyzed (Mouyna, I., Hartland, R. P., Fontaine, T., Diaquin, M., Simenel, C., Delepierre, M., Henrissat, B., and Latgé, J. P. (1998) Microbiology 144, 3171-3180). Both enzymes release laminaribiose from the reducing end of a beta(1-3)-linked oligosaccharide and transfer the remaining chain to another molecule of the original substrate. The AfBgt1p transfer occurs at C-6 of the non-reducing end group of the acceptor, creating a kinked beta(1-3;1-6) linear molecule. The AfBgt2p transfer takes place at the C-6 of an internal group of the acceptor, resulting in a beta(1-3)-linked product with a beta(1-6)-linked side branch. The single Afbgt2 mutant and the double Afbgt1/Afbgt2 mutant in A. fumigatus did not display any cell wall phenotype showing that these activities were not responsible for the construction of the branched beta(1-3)-glucans of the cell wall.


Asunto(s)
Aspergillus fumigatus/enzimología , Glucano Endo-1,3-beta-D-Glucosidasa/aislamiento & purificación , Glucano Endo-1,3-beta-D-Glucosidasa/metabolismo , beta-Glucanos/aislamiento & purificación , beta-Glucanos/metabolismo , Aspergillus fumigatus/genética , Western Blotting , Pared Celular/enzimología , Celulasas/metabolismo , Cromatografía Líquida de Alta Presión/métodos , Electroforesis en Gel de Poliacrilamida , Proteínas Fúngicas/genética , Proteínas Fúngicas/aislamiento & purificación , Proteínas Fúngicas/metabolismo , Cromatografía de Gases y Espectrometría de Masas , Glucano Endo-1,3-beta-D-Glucosidasa/genética , Glicosilación , Mutación , Resonancia Magnética Nuclear Biomolecular , Fenotipo
17.
Carbohydr Res ; 344(15): 1960-7, 2009 Oct 12.
Artículo en Inglés | MEDLINE | ID: mdl-19709651

RESUMEN

A glucuronic acid containing glycerolipid was isolated from the filamentous fungi Aspergillus fumigatus. This acidic glycolipid was extracted from the membrane of mycelium and purified by two successive chromatographic steps on DEAE-Sephadex and Silica columns. Chemical structural analysis was performed using methylation, gas-chromatography, gas-chromatography-mass spectrometry, nano-electrospray mass spectrometry and (1)H/(13)C NMR spectra. The corresponding structure is a 3-(O-alpha-glucuronyl)-1,2-diacyl-sn-glycerol, where acyl chains are mainly C(16:0), C(18:0), C(18:1), and C(18:2). This alpha-GlcA-diacylglycerol is not present in fungal conidia. This acidic glycerolipid is described here for the first time in a fungal species. Two homologs of UDP-glucose dehydrogenase that convert UDP-glucose into UDP-glucuronic acid, are present in A. fumigatus genome, UGD1 and UGD2. Gene deletion showed that only UGD1 is essential for the biosynthesis of GlcA-DG. However, no particular phenotype has been observed in the Ugd1Delta mutant. Biological function of this acidic glycolipid remains unknown in A. fumigatus.


Asunto(s)
Aspergillus fumigatus/metabolismo , Ácido Glucurónico/química , Glucolípidos/química , Micelio/metabolismo , Aspergillus fumigatus/genética , Cromatografía de Gases , Cromatografía de Gases y Espectrometría de Masas , Glucolípidos/genética , Glucolípidos/metabolismo , Espectroscopía de Resonancia Magnética , Estructura Molecular , Micelio/genética
18.
Biomol NMR Assign ; 3(1): 45-8, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-19636944

RESUMEN

Most of microbes hijack the cellular machinery to their advantage by interacting with specific target of the host cell. Glycoprotein of rabies virus is a key factor controlling the homeostasis of infected neuronal cells and proteins belonging to the human microtubule associated serine threonine kinase family have been identified as potential cellular partners. As a first step towards its structural study, we have assigned the backbone and side chain nuclei resonances of the PDZ domain (PSD-95, Discs Large, ZO-1) of MAST205 in complex with the C-terminal residues of the glycoprotein of rabies virus. The BMRB accession code is 155972.


Asunto(s)
Glicoproteínas/química , Espectroscopía de Resonancia Magnética/métodos , Proteínas Asociadas a Microtúbulos/química , Proteínas Serina-Treonina Quinasas/química , Virus de la Rabia/química , Proteínas Virales/química , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Sitios de Unión , Isótopos de Carbono/química , Datos de Secuencia Molecular , Complejos Multiproteicos/química , Isótopos de Nitrógeno/química , Unión Proteica , Estructura Terciaria de Proteína , Protones
19.
J Biol Chem ; 284(20): 13401-13412, 2009 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-19279004

RESUMEN

Despite its essential role in the yeast cell wall, the exact composition of the beta-(1,6)-glucan component is not well characterized. While solubilizing the cell wall alkali-insoluble fraction from a wild type strain of Saccharomyces cerevisiae using a recombinant beta-(1,3)-glucanase followed by chromatographic characterization of the digest on an anion exchange column, we observed a soluble polymer that eluted at the end of the solvent gradient run. Further characterization indicated this soluble polymer to have a molecular mass of approximately 38 kDa and could be hydrolyzed only by beta-(1,6)-glucanase. Gas chromatography mass spectrometry and NMR ((1)H and (13)C) analyses confirmed it to be a beta-(1,6)-glucan polymer with, on average, branching at every fifth residue with one or two beta-(1,3)-linked glucose units in the side chain. This polymer peak was significantly reduced in the corresponding digests from mutants of the kre genes (kre9 and kre5) that are known to play a crucial role in the beta-(1,6)-glucan biosynthesis. In the current study, we have developed a biochemical assay wherein incubation of UDP-[(14)C]glucose with permeabilized S. cerevisiae yeasts resulted in the synthesis of a polymer chemically identical to the branched beta-(1,6)-glucan isolated from the cell wall. Using this assay, parameters essential for beta-(1,6)-glucan synthetic activity were defined.


Asunto(s)
Pared Celular/química , Pared Celular/metabolismo , Glucanos/biosíntesis , Glucanos/química , Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/metabolismo , Conformación de Carbohidratos , Pared Celular/genética , Glucanos/genética , Glucanos/aislamiento & purificación , Glicoproteínas/genética , Glicoproteínas/metabolismo , Glicósido Hidrolasas/química , Espectroscopía de Resonancia Magnética/métodos , Peso Molecular , Mutación , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo
20.
Glycobiology ; 18(1): 84-96, 2008 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-17971386

RESUMEN

Fungal glycosylinositolphosphoceramides (GIPCs) are involved in cell growth and fungal-host interactions. In this study, six GIPCs from the mycelium of the human pathogen Aspergillus fumigatus were purified and characterized using Q-TOF mass spectrometry and 1H, 13C, and 31P NMR. All structures have the same inositolphosphoceramide moiety with the presence of a C(18:0)-phytosphingosine conjugated to a 2-hydroxylated saturated fatty acid (2-hydroxy-lignoceric acid). The carbohydrate moiety defines two types of GIPC. The first, a mannosylated zwitterionic glycosphingolipid contains a glucosamine residue linked in alpha1-2 to an inositol ring that has been described in only two other fungal pathogens. The second type of GIPC presents an alpha-Manp-(1-->3)-alpha-Manp-(1-->2)-IPC common core. A galactofuranose residue is found in four GIPC structures, mainly at the terminal position via a beta1-2 linkage. Interestingly, this galactofuranose residue could be substituted by a choline-phosphate group, as observed only in the GIPC of Acremonium sp., a plant pathogen.


Asunto(s)
Aspergillus fumigatus/química , Glicoesfingolípidos/química , Aspergillus fumigatus/metabolismo , Glicoesfingolípidos/aislamiento & purificación , Glicoesfingolípidos/metabolismo , Resonancia Magnética Nuclear Biomolecular , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...