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1.
Sci Total Environ ; 901: 165887, 2023 Nov 25.
Artículo en Inglés | MEDLINE | ID: mdl-37517715

RESUMEN

Understanding how Mediterranean forests respond to the increasing frequency of extreme droughts and forest densification is crucial for effective land management in the present context of climate change and land abandonment. We study the responses of Iberian holm oak (Quercus ilex L.) woodlands to recent extreme droughts during 2000-2019 along broad gradients of climate aridity and forest structure. To this purpose, we apply large-scale remote-sensing using MODIS EVI as a primary production proxy in 5274 Q. ilex sites distributed within a 100,000 km2 region in eastern Spain. These woodlands were extensively affected by two extreme drought events in 2005 and 2012. Resistance, assessed as the capacity of the ecosystems to maintain primary production during drought, was significantly lower for semi-arid than for sub-humid and dry-transition conditions. Holm oak woodlands located in semi-arid areas of the region showed also poorer resilience to drought, characterized by low capacity to fully recover to their pre-drought production levels. Further, drought intensity and both pre- and post-drought hydric conditions controlled the variations of resistance, recovery and resilience between the two analyzed extreme drought events. Drought effects were particularly negative for dense Q. ilex stands under semi-arid climate conditions, where strong competition for scarce water resources reduced drought resistance. The observed drought vulnerability of semi-arid holm oak woodlands may affect the long-term stability of these dry forests. Adaptive management strategies, such as selective forest thinning, may be useful for improving drought responses in these more vulnerable semi-arid woodlands. Conversely, natural rewilding may more appropriately guide management actions for more humid areas, where densely developed Q. ilex woodlands show in general a high ability to maintain ecosystem primary production during drought.


Asunto(s)
Ecosistema , Quercus , Sequías , Quercus/fisiología , España , Bosques , Cambio Climático , Árboles/fisiología
3.
Eur J Cardiovasc Nurs ; 18(7): 621-627, 2019 10.
Artículo en Inglés | MEDLINE | ID: mdl-31148459

RESUMEN

BACKGROUND: Heart failure with preserved ejection fraction is a clinical syndrome characterised by reduced exercise capacity. Some evidence has shown that a simple and home-based programme of inspiratory muscle training offers promising results in terms of aerobic capacity improvement in patients with heart failure with preserved ejection fraction. This study aimed to investigate whether the baseline inspiratory muscle function predicts the changes in aerobic capacity (measured as peak oxygen uptake; peak VO2) after a 12-week home-based programme of inspiratory muscle training in patients with heart failure with preserved ejection fraction. METHODS: A total of 45 stable symptomatic patients with heart failure with preserved ejection fraction and New York Heart Association II-III received a 12-week home-based programme of inspiratory muscle training between June 2015 and December 2016. They underwent cardiopulmonary exercise testing and measurements of maximum inspiratory pressure pre and post-inspiratory muscle training. Maximum inspiratory pressure and peak VO2 were registered in both visits. Multivariate linear regression analysis was used to assess the association between changes in peak VO2 (Δ-peakVO2) and baseline predicted maximum inspiratory pressure (pp-MIP). RESULTS: The median (interquartile range) age was 73 (68-77) years, 47% were women and 35.6% displayed New York Heart Association III. The mean peak VO2 at baseline and Δ-peakVO2 post-training were 10.4±2.8 ml/min/kg and +2.2±1.3 ml/min/kg (+21.3%), respectively. The median (interquartile range) of pp-MIP and Δ-MIP were 71% (64-92) and 39.2 (26.7-80.4) cmH2O, respectively. After a multivariate analysis, baseline pp-MIP was not associated with Δ-peakVO2 (ß coefficient 0.005, 95% confidence interval -0.009-0.019, P=0.452). CONCLUSIONS: In symptomatic and deconditioned older patients with heart failure with preserved ejection fraction, a home-based inspiratory muscle training programme improves aerobic capacity regardless of the baseline maximum inspiratory pressure.


Asunto(s)
Ejercicios Respiratorios/métodos , Tolerancia al Ejercicio/fisiología , Insuficiencia Cardíaca/rehabilitación , Contracción Muscular/fisiología , Enfermería en Rehabilitación/métodos , Volumen Sistólico/fisiología , Anciano , Femenino , Humanos , Masculino
4.
Neurobiol Stress ; 9: 40-47, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30450372

RESUMEN

Exercise has been shown to reduce the risk of developing Mild Cognitive Impairment and Alzheimer's disease as well as to improve cognition in healthy and cognitively impaired individuals. However, the mechanisms of these benefits are not well understood. The stress hypothesis suggests that the cognitive benefits attributed to exercise may partially be mediated by changes in the cortisol secretion pattern. Chronic stress may increase the risk of AD and exacerbate the cognitive deficits and brain pathology characteristic of the condition while physical activity has been shown to attenuate most of stress consequences and risk factors for AD. Initially, research on the effects of cortisol on cognition and physical activity focused on cortisol levels at one time point but the circadian pattern of cortisol secretion is complex and it is still unclear which aspects are most closely associated with cognitive function. Thus, the aim of this review was to analyze the exercise/stress/cognition hypothesis focusing on the effects of the diurnal cycle of cortisol on cognitive function and physical activity in older adults with and without cognitive impairment.

5.
Artículo en Inglés | MEDLINE | ID: mdl-28515793

RESUMEN

BACKGROUND: Regular physical activity is a promising strategy to treat and prevent cognitive decline. The mechanisms that mediate these benefits are not fully clear but physical activity is thought to attenuate the harmful effects of chronic psychological stress and hypercortisolism on cognition. However, the circadian pattern of cortisol secretion is complex and it is not known which aspects are most closely associated with increased cognitive function and better physical performance. This is the first study to simultaneously measure cognitive function, the diurnal cycle of salivary cortisol and physical performance in older adults, without cognitive impairment (n = 30) and with amnestic Mild Cognitive Impairment (aMCI) (n = 30). RESULTS: Regression analysis showed that better cognitive function was associated with better physical performance. A greater variance in cortisol levels across the day from morning to evening was associated with better cognitive function and physical performance. CONCLUSIONS: The results support the idea that a more dynamic cortisol secretion pattern is associated with better cognitive function and physical performance even in the presence of cognitive impairment, but our results could not confirm a mediating role in this relationship.

6.
Biol Sport ; 32(3): 219-23, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-26424925

RESUMEN

The use of graduated compression stockings (GCS) in sport has been increasing in the last years due to their potential positive effects for athletes. However, there is little evidence to support whether these types of garments actually improve cardiorespiratory performance. The aim of this study was to examine the cardiorespiratory responses of GCS during running after three weeks of regular use. Twenty recreational runners performed three tests on different days: test 1) - a 5-min maximal effort run in order to determine the participants' maximal aerobic speed; and tests 2) and 3) - a fatigue running test of 30 minutes at 80% of their maximal aerobic speed with either GCS or PLACEBO stockings at random. Cardiorespiratory parameters (minute ventilation, heart rate, relative oxygen consumption, relative carbon dioxide production, ventilatory equivalents for oxygen and carbon dioxide, and oxygen pulse) were measured. Before each test in the laboratory, the participants trained with the randomly assigned stockings (GCS or PLACEBO) for three weeks. No significant differences between GCS and PLACEBO were found in any of the cardiorespiratory parameters. In conclusion, the present study provides evidence that running with GCS for three weeks does not influence cardiorespiratory parameters in recreational runners.

7.
An Pediatr (Barc) ; 82(1): e184-8, 2015 Jan.
Artículo en Español | MEDLINE | ID: mdl-25453310

RESUMEN

Xanthogranulomatous pyelonephritis is a rare inflammatory disease, characterized by replacement of renal parenchyma with granulomatous tissue. Initial clinical presentation includes abdominal pain and constitutional symptoms related to recurrent urinary infections. The microorganisms most commonly involved are Escherichia coli and Proteus mirabilis. Final diagnosis is made by histopathology, and the only curative treatment is total or partial nephrectomy. A recently diagnosed case in our unit is presented, as well as an update on the knowledge of this disease.


Asunto(s)
Pielonefritis Xantogranulomatosa/diagnóstico , Preescolar , Femenino , Fiebre/complicaciones , Humanos , Desnutrición/complicaciones , Pielonefritis Xantogranulomatosa/complicaciones , Recurrencia , Índice de Severidad de la Enfermedad
8.
J Biomol Screen ; 20(1): 82-91, 2015 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25332350

RESUMEN

African trypanosomiasis, leishmaniasis, and Chagas disease are 3 neglected tropical diseases for which current therapeutic interventions are inadequate or toxic. There is an urgent need to find new lead compounds against these diseases. Most drug discovery strategies rely on high-throughput screening (HTS) of synthetic chemical libraries using phenotypic and target-based approaches. Combinatorial chemistry libraries contain hundreds of thousands of compounds; however, they lack the structural diversity required to find entirely novel chemotypes. Natural products, in contrast, are a highly underexplored pool of unique chemical diversity that can serve as excellent templates for the synthesis of novel, biologically active molecules. We report here a validated HTS platform for the screening of microbial extracts against the 3 diseases. We have used this platform in a pilot project to screen a subset (5976) of microbial extracts from the MEDINA Natural Products library. Tandem liquid chromatography-mass spectrometry showed that 48 extracts contain potentially new compounds that are currently undergoing de-replication for future isolation and characterization. Known active components included actinomycin D, bafilomycin B1, chromomycin A3, echinomycin, hygrolidin, and nonactins, among others. The report here is, to our knowledge, the first HTS of microbial natural product extracts against the above-mentioned kinetoplastid parasites.


Asunto(s)
Antiprotozoarios/farmacología , Productos Biológicos/farmacología , Descubrimiento de Drogas/métodos , Ensayos Analíticos de Alto Rendimiento/métodos , Leishmania/efectos de los fármacos , Trypanosoma brucei gambiense/efectos de los fármacos , Trypanosoma cruzi/efectos de los fármacos , Animales , Antiprotozoarios/uso terapéutico , Productos Biológicos/uso terapéutico , Enfermedad de Chagas/tratamiento farmacológico , Relación Dosis-Respuesta a Droga , Descubrimiento de Drogas/normas , Ensayos Analíticos de Alto Rendimiento/normas , Humanos , Concentración 50 Inhibidora , Leishmaniasis/tratamiento farmacológico , Enfermedades Desatendidas/tratamiento farmacológico , Tripanosomiasis Africana/tratamiento farmacológico
9.
Ann Bot ; 105(4): 627-35, 2010 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-20181568

RESUMEN

BACKGROUND AND AIMS: The role of fire as a germination cue for Mediterranean Basin (MB) plants is still unclear. The current idea is that heat stimulates germination mainly in Cistaceae and Fabaceae and that smoke has a limited role as a post-fire germination cue, in comparison with other Mediterranean-type ecosystems (MTEs), suggesting that fire-stimulated germination is less relevant in the MB than in other MTEs. However, recent studies showed that the assembly of Mediterranean plant communities is strongly driven by post-fire germination, suggesting an important role for fire as a germination cue. We hypothesize that both heat and smoke have important effects on the different post-fire recruitment processes of MB species (e.g. level and rate of germination and initial seedling growth). METHODS: To ascertain the role of heat and smoke in the post-fire germination response of MB woody plants, a germination experiment was performed with seven heat and two smoke treatments on 30 MB woody species from seven different families, including species with water-permeable seeds and species with water-impermeable seeds. KEY RESULTS: Heat stimulated the germination (probability and rate) of 21 species and smoke in eight species, out of the 30 species studied. In addition, six species showed enhanced initial seedling growth after the smoke treatments. CONCLUSIONS: The results suggest that both heat and smoke are important germination cues in a wide range of MB woody species and that fire-cued germination in woody plants of the MB may be as important as in other MTEs.


Asunto(s)
Incendios , Germinación/fisiología , Calor , Desarrollo de la Planta , Humo , Región Mediterránea , Plantones/crecimiento & desarrollo , Semillas/crecimiento & desarrollo
10.
Mycologia ; 101(4): 449-72, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19623926

RESUMEN

Evaluation of fungal fermentation extracts with whole cell Candida albicans activity resulted in the identification of a novel class of isoxazolidinone-containing metabolites named parnafungins. Chemical-genetic profiling with the C. albicans fitness test identified the biochemical target as inhibition of polyadenosine polymerase, a component of the mRNA cleavage and polyadenylation complex. Parnafungins were discovered from fermentation extracts of fungi resembling F. larvarum isolated from plants, plant litter and lichens. Furthermore authentic strains of F. larvarum var. larvarum and F. larvarum var. rubrum could be induced to produce parnafungins and their degradation products in low titers. Relationships among strains of the F. larvarum complex (FLC), including parnafungin-producing strains, were examined by cladistic analyses of rDNA, mitochondrial rDNA, and two protein-coding genes, comparisons of antifungal activity and antifungal metabolite profiles, and morphological phenotypes. Integrated analyses of these data led to the conclusion that the diversity within the FLC exceeded the one-to-one correspondence between F. larvarum and its teleomorph Cosmospora aurantiicola. Based on multiple gene sequence analyses, strains of the FLC formed a monophyletic clade inclusive of the parnafungin-producing strains. The FLC, including newly discovered parnafungin-producing strains, could be resolved into at least six different lineages, possibly representing cryptic' species, of which one was not fully resolved from F. larvarum var. rubrum. Fusarium larvarum var. rubrum represents a species distinct from var. larvarum. Finally we report that two other species from the Hypocreales, Trichonectria rectipila and Cladobotryum pinarense, are able to produce parnafungins and their open-ring forms.


Asunto(s)
Fusarium/clasificación , Fusarium/metabolismo , Oxazolidinonas/metabolismo , Poliadenilación , ARN Mensajero/metabolismo , ADN de Hongos/genética , ADN Mitocondrial/genética , ADN Ribosómico/genética , Fusarium/genética , Genes Fúngicos , Variación Genética , Espectrometría de Masas , Filogenia , Análisis de Secuencia de ADN , Esporas Fúngicas/citología
11.
J Appl Microbiol ; 104(6): 1644-58, 2008 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-18298532

RESUMEN

AIMS: We asked to what extent does the application of the OSMAC (one strain, many compounds) approach lead to enhanced detection of antibiotics and secondary metabolites in fungi? Protocols for bacterial microfermentations were adapted to grow fungi in nutritional arrays. METHODS AND RESULTS: Protocols for microfermentations of non-sporulating fungi were validated using known antifungal-producing fungi. Detection of antifungal activity was often medium dependent. The effects of medium arrays and numbers of strains on detection of antifungal signals were modelled by interpolation of rarefaction curves derived from matrices of positive and negative extracts. Increasing the number of fermentation media for any given strain increased the probability of detection of growth inhibition of Candida albicans. Increasing biodiversity increased detection of antifungal phenotypes, however, nutritional arrays could partly compensate for lost antibiotic phenotypes when biodiversity was limiting. CONCLUSIONS: Growth and extraction in microtiter plates can enable a discovery strategy emphasizing low-cost medium arrays that can better exploit the metabolic potential of strains. SIGNIFICANCE AND IMPACT OF THE STUDY: Increasing fermentation parameters raise the probability of detecting bioactive metabolites from strains. The protocols can be used to pre-select strains and their growth conditions for scale up that will most likely yield antibiotics and secondary metabolites.


Asunto(s)
Antifúngicos/análisis , Hongos/metabolismo , Antifúngicos/química , Reactores Biológicos/microbiología , Candida albicans/efectos de los fármacos , Candida albicans/crecimiento & desarrollo , Medios de Cultivo , Fermentación , Pruebas de Sensibilidad Microbiana , Micología/instrumentación , Micología/métodos
12.
Mycologia ; 98(4): 616-27, 2006.
Artículo en Inglés | MEDLINE | ID: mdl-17139855

RESUMEN

A new coelomycete, Morinia longiappendiculata sp. nov., isolated from living stems of four plant species in central Spain, is described. The distinctive morphological characteristics of this fungus are the production of conidia with long basal and apical appendages on filiform conidiogenous cells that contrasts with the short-appendaged conidia and cylindrical conidiogenic cells of the type species, M. pestalozzioides. Comparative sequence analysis of the ITS rDNA region and fragments of the translation elongation factor 1alpha, actin and chitin synthase 1 genes and the study of the HPLC profiles of the M. longiappendiculata and M. pestalozzioides isolates supported the recognition of the new species. Comparison of the ITS rDNA sequences of the Morinia isolates with GenBank sequences indicated that the genus belongs to the Amphisphaeriaceae with the highest similarity to Bartalinia and Truncatella. Bresadola's original definition of M. pestalozzioides is updated by adding information on conidiogenesis and molecular data. A lectotype and epitype are designated for the species. A study of bioactive metabolites revealed that M. pestalozzioides cultures produced moriniafungin, a novel sordarin analog with potent antifungal activity.


Asunto(s)
Magnoliopsida/microbiología , Xylariales/clasificación , Actinas/genética , Quitina Sintasa/genética , Cromatografía Líquida de Alta Presión , ADN Espaciador Ribosómico/genética , Factores Eucarióticos de Iniciación/genética , Indenos/metabolismo , Tallos de la Planta/microbiología , Esporas Fúngicas/citología , Xylariales/química , Xylariales/citología , Xylariales/genética
13.
Bioorg Med Chem ; 14(2): 560-6, 2006 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-16183294

RESUMEN

A novel sordarin derivative, moriniafungin (1), containing a 2-hydroxysebacic acid residue linked to C-3' of the sordarose residue of sordarin through a 1,3-dioxolan-4-one ring was isolated from the fungus Morinia pestalozzioides. Isolation of moriniafungin employed a highly specific bioassay consisting of a panel of Saccharomyces cerevisiae strains containing chimeric eEF2 for Candida glabrata, Candida krusei, Candida lusitaniae, Crytpococcus neoformans, and Aspergillus fumigatus as well as wild type and human eEF2. Moriniafungin exhibited an MIC of 6 microg/mL versus Candida albicans and IC(50)'s ranging from 0.9 to 70 microg/mL against a panel of clinically relevant Candida strains. Moriniafungin was shown to inhibit in vitro translation in the chimeric S. cerevisae strains at levels consistent with the observed IC(50). Moriniafungin has the broadest antifungal spectrum and most potent activity of any natural sordarin analog identified to date.


Asunto(s)
Antifúngicos/química , Hongos/química , Indenos/química , Antifúngicos/farmacología , Fermentación , Hongos/efectos de los fármacos , Indenos/farmacología , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Saccharomyces cerevisiae/efectos de los fármacos
14.
Farm Hosp ; 28(4): 286-90, 2004.
Artículo en Español | MEDLINE | ID: mdl-15369439

RESUMEN

OBJECTIVE: To establish the percentage of Pharmacy Departments with a web site on the Net, and to analyze whether their contents are focused on the development of pharmaceutical care activities for outpatients. METHODS: Cross-sectional study based on multiple Internet searches using the Copernic version 6.0 software, as well as on directories listing hospital- and pharmacy department-owned web sites. RESULTS: Amongst 452 hospitals with 100 or more beds, 198 (43.8%) hospital web pages and 52 (11.52%) pharmacy department web sites were found. The contents of pharmacy department sites were usually deficient, and only rarely was interaction with outpatients envisaged. CONCLUSION: The presence of pharmacy departments on the Internet is scarce. Telepharmacy or pharmaceutical care for outpatients using novel information technologies remains underdeveloped by Spanish pharmacy departments.


Asunto(s)
Internet/estadística & datos numéricos , Servicio de Farmacia en Hospital/estadística & datos numéricos , Atención Ambulatoria , Estudios Transversales , Difusión de Innovaciones , Relaciones Paciente-Hospital , Humanos , Internet/normas , Pacientes Ambulatorios , Servicio de Farmacia en Hospital/métodos , Control de Calidad , Programas Informáticos , España
15.
An Med Interna ; 20(8): 396-8, 2003 Aug.
Artículo en Español | MEDLINE | ID: mdl-14516258

RESUMEN

INTRODUCTION: The ingestion of alcohol produces oxydative stress generating free radicals of oxygen and ethanol. These free radicals have a molecular reactive ability and, therefore, they play an important role in the production of the injury which appears in the liver and in other organs and tissues. We have done an "in vitro" study where we analyse the oxydative status at rest and the respiratory explosion produced by ethanol at final concentrations of 50 and 25 mM and by the phagocytosis of a previously opsonized concentrate of bacteria (E.coli) in human leucocytes taken from peripheral blood of six healthy persons. METHOD: We have used 1.2.3. dihydrorhodamine (non-fluorescent) as the oxydative marker because it is transformed in rhodamine (fluorescent), which is quantitatively studied by Flow Cytometry. RESULTS: The peak of oxydative stress is reached with the bacteria in the phagocytes (monocytes 50% and granulocytes 90%) and it has a significant difference with the control group. By adding ethanol at 50 mM we have seen an statistic significant difference in oxydative stress in the cells of all three types (lymphocytes 9.19%, monocytes 32% and granulocytes 36%). With a concentration of 25 mM of ethanol the oxydative stress is increased but without a significant difference (lymphocytes 2.39%, monocytes 9.22% and granulocytes 4.46%). We have also seen toxic cellular effect which reaches the 40.75% of cells with ethanol at 50 mM, the 10.7% with ethanol at 25 mM and the 5.65% with bacteria. CONCLUSION: The oxydative stress caused by the production of oxygen and ethanol free radicals in the leucocytes, and the proved cytotoxic effect of ethanol may play an important role over the qualitative and the quantitative leucocyte disorder on different organs and tissues of the alcoholic patient.


Asunto(s)
Etanol/toxicidad , Radicales Libres/sangre , Leucocitos/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Citometría de Flujo , Humanos
17.
Bioorg Med Chem Lett ; 11(5): 681-4, 2001 Mar 12.
Artículo en Inglés | MEDLINE | ID: mdl-11266168

RESUMEN

To study the relevance of the terminal alpha,beta-unsaturated gamma-methyl-gamma-lactone moiety of the antitumoral acetogenins of Annonaceae for potent mitochondrial complex I inhibition, we have prepared a series of semisynthetic acetogenins with modifications only in this part of the molecule, from the natural rolliniastatin-1 (1) and cherimolin-1 (2). Some of the hydroxylated derivatives (1b, 1d and 1e) in addition to two infrequent natural beta-hydroxy gamma-methyl gamma-lactone acetogenins, laherradurin (3) and itrabin (4), are more potent complex I inhibitors than any other known compounds.


Asunto(s)
Antineoplásicos/química , Furanos/química , Lactonas/química , Mitocondrias Cardíacas/enzimología , NADH NADPH Oxidorreductasas/antagonistas & inhibidores , Animales , Antineoplásicos/síntesis química , Antineoplásicos/farmacología , Bovinos , Complejo I de Transporte de Electrón , Furanos/síntesis química , Furanos/farmacología , Lactonas/síntesis química , Lactonas/farmacología , Magnoliopsida/química , Mitocondrias Cardíacas/efectos de los fármacos , Estructura Molecular , Complejos Multienzimáticos/antagonistas & inhibidores , Complejos Multienzimáticos/metabolismo , NADH NADPH Oxidorreductasas/metabolismo , Partículas Submitocóndricas/efectos de los fármacos , Partículas Submitocóndricas/enzimología
18.
J Biol Chem ; 276(10): 7312-9, 2001 Mar 09.
Artículo en Inglés | MEDLINE | ID: mdl-11036086

RESUMEN

CD69, one of the earliest specific antigens acquired during lymphoid activation, acts as a signal-transducing receptor involved in cellular activation events, including proliferation and induction of specific genes. CD69 belongs to a family of receptors that modulate the immune response and whose genes are clustered in the natural killer (NK) gene complex. The extracellular portion of these receptors represent a subfamily of C-type lectin-like domains (CTLDs), which are divergent from true C-type lectins and are referred to as NK-cell domains (NKDs). We have determined the three-dimensional structure of human CD69 NKD in two different crystal forms. CD69 NKD adopts the canonical CTLD fold but lacks the features involved in Ca(2+) and carbohydrate binding by C-type lectins. CD69 NKD dimerizes noncovalently, both in solution and in crystalline state. The dimer interface consists of a hydrophobic, loosely packed core, surrounded by polar interactions, including an interdomain beta sheet. The intersubunit core shows certain structural plasticity that may facilitate conformational rearrangements for binding to ligands. The surface equivalent to the binding site of other members of the CTLD superfamily reveals a hydrophobic patch surrounded by conserved charged residues that probably constitutes the CD69 ligand-binding site.


Asunto(s)
Antígenos CD/química , Antígenos de Diferenciación de Linfocitos T/química , Lectinas/química , Secuencia de Aminoácidos , Animales , Sitios de Unión , División Celular , Cristalografía por Rayos X , Dimerización , Electrones , Humanos , Células Asesinas Naturales/metabolismo , Lectinas Tipo C , Ligandos , Modelos Moleculares , Datos de Secuencia Molecular , Plásmidos/metabolismo , Unión Proteica , Pliegue de Proteína , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Ratas , Proteínas Recombinantes/metabolismo , Homología de Secuencia de Aminoácido , Transducción de Señal
19.
Biochemistry ; 39(50): 15375-87, 2000 Dec 19.
Artículo en Inglés | MEDLINE | ID: mdl-11112523

RESUMEN

Antigen-antibody complexes provide useful models for analyzing the thermodynamics of protein-protein association reactions. We have employed site-directed mutagenesis, X-ray crystallography, and isothermal titration calorimetry to investigate the role of hydrophobic interactions in stabilizing the complex between the Fv fragment of the anti-hen egg white lysozyme (HEL) antibody D1.3 and HEL. Crystal structures of six FvD1.3-HEL mutant complexes in which an interface tryptophan residue (V(L)W92) has been replaced by residues with smaller side chains (alanine, serine, valine, aspartate, histidine, and phenylalanine) were determined to resolutions between 1.75 and 2.00 A. In the wild-type complex, V(L)W92 occupies a large hydrophobic pocket on the surface of HEL and constitutes an energetic "hot spot" for antigen binding. The losses in apolar buried surface area in the mutant complexes, relative to wild-type, range from 25 (V(L)F92) to 115 A(2) (V(L)A92), with no significant shifts in the positions of protein atoms at the mutation site for any of the complexes except V(L)A92, where there is a peptide flip. The affinities of the mutant Fv fragments for HEL are 10-100-fold lower than that of the original antibody. Formation of all six mutant complexes is marked by a decrease in binding enthalpy that exceeds the decrease in binding free energy, such that the loss in enthalpy is partly offset by a compensating gain in entropy. No correlation was observed between decreases in apolar, polar, or aggregate (sum of the apolar and polar) buried surface area in the V(L)92 mutant series and changes in the enthalpy of formation. Conversely, there exist linear correlations between losses of apolar buried surface and decreases in binding free energy (R(2) = 0.937) as well as increases in the solvent portion of the entropy of binding (R(2) = 0.909). The correlation between binding free energy and apolar buried surface area corresponds to 21 cal mol(-1) A(-2) (1 cal = 4.185 J) for the effective hydrophobicity at the V(L)92 mutation site. Furthermore, the slope of the line defined by the correlation between changes in binding free energy and solvent entropy approaches unity, demonstrating that the exclusion of solvent from the binding interface is the predominant energetic factor in the formation of this protein complex. Our estimate of the hydrophobic contribution to binding at site V(L)92 in the D1.3-HEL interface is consistent with values for the hydrophobic effect derived from classical hydrocarbon solubility models. We also show how residue V(L)W92 can contribute significantly less to stabilization when buried in a more polar pocket, illustrating the dependence of the hydrophobic effect on local environment at different sites in a protein-protein interface.


Asunto(s)
Complejo Antígeno-Anticuerpo/química , Animales , Complejo Antígeno-Anticuerpo/inmunología , Sitios de Unión de Anticuerpos , Cristalografía por Rayos X , Ratones , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Unión Proteica/inmunología , Conformación Proteica , Termodinámica
20.
J Immunol ; 165(12): 6922-32, 2000 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-11120818

RESUMEN

We have used a recombinant, biotinylated form of the mouse NK cell inhibitory receptor, Ly49A, to visualize the expression of MHC class I (MHC-I) ligands on living lymphoid cells. A panel of murine strains, including MHC congenic lines, was examined. We detected binding of Ly49A to cells expressing H-2D(d), H-2D(k), and H-2D(p) but not to those expressing other MHC molecules. Cells of the MHC-recombinant strain B10.PL (H-2(u)) not only bound Ly49A but also inhibited cytolysis by Ly49A(+) effector cells, consistent with the correlation of in vitro binding and NK cell function. Binding of Ly49A to H-2D(d)-bearing cells of different lymphoid tissues was proportional to the level of H-2D(d) expression and was not related to the lineage of the cells examined. These binding results, interpreted in the context of amino acid sequence comparisons and the recently determined three-dimensional structure of the Ly49A/H-2D(d) complex, suggest a role for amino acid residues at the amino-terminal end of the alpha1 helix of the MHC-I molecule for Ly49A interaction. This view is supported by a marked decrease in affinity of an H-2D(d) mutant, I52 M, for Ly49A. Thus, allelic variation of MHC-I molecules controls measurable affinity for the NK inhibitory receptor Ly49A and explains differences in functional recognition in different mouse strains.


Asunto(s)
Antígenos Ly , Proteínas Portadoras/metabolismo , Mapeo Epitopo/métodos , Antígenos H-2/metabolismo , Células Asesinas Naturales/metabolismo , Proteínas de la Membrana/metabolismo , Secuencia de Aminoácidos , Animales , Biotinilación , Proteínas Portadoras/análisis , Epítopos/análisis , Antígenos H-2/análisis , Antígenos H-2/biosíntesis , Antígenos H-2/genética , Antígeno de Histocompatibilidad H-2D , Células Asesinas Naturales/inmunología , Lectinas Tipo C , Ligandos , Ganglios Linfáticos/química , Ganglios Linfáticos/citología , Ganglios Linfáticos/inmunología , Ganglios Linfáticos/metabolismo , Subgrupos Linfocitarios/química , Subgrupos Linfocitarios/inmunología , Subgrupos Linfocitarios/metabolismo , Proteínas de la Membrana/análisis , Ratones , Ratones Endogámicos A , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Transgénicos , Mutagénesis Sitio-Dirigida , Subfamilia A de Receptores Similares a Lectina de Células NK , Receptores Similares a Lectina de Células NK , Alineación de Secuencia , Solubilidad , Coloración y Etiquetado/métodos , Células Tumorales Cultivadas
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