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1.
J Am Soc Nephrol ; 34(3): 505-514, 2023 03 01.
Artículo en Inglés | MEDLINE | ID: mdl-36446430

RESUMEN

SIGNIFICANCE STATEMENT: Most patients with anti-glomerular basement membrane (GBM) disease present with rapidly progressive glomerulonephritis, and more than half develop ESKD. Currently, no tools are available to aid in the prognostication or management of this rare disease. In one of the largest assembled cohorts of patients with anti-GBM disease (with 174 patients included in the final analysis), the authors demonstrated that the renal risk score for ANCA-associated vasculitis is transferable to anti-GBM disease and the renal histology is strongly predictive of renal survival and recovery. Stratifying patients according to the percentage of normal glomeruli in the kidney biopsy and the need for RRT at the time of diagnosis improves outcome prediction. Such stratification may assist in the management of anti-GBM disease. BACKGROUND: Prospective randomized trials investigating treatments and outcomes in anti-glomerular basement membrane (anti-GBM) disease are sparse, and validated tools to aid prognostication or management are lacking. METHODS: In a retrospective, multicenter, international cohort study, we investigated clinical and histologic parameters predicting kidney outcome and sought to identify patients who benefit from rescue immunosuppressive therapy. We also explored applying the concept of the renal risk score (RRS), currently used to predict renal outcomes in ANCA-associated vasculitis, to anti-GBM disease. RESULTS: The final analysis included 174 patients (out of a total of 191). Using Cox and Kaplan-Meier methods, we found that the RRS was a strong predictor for ESKD. The 36-month renal survival was 100%, 62.4%, and 20.7% in the low-risk, moderate-risk, and high-risk groups, respectively. The need for renal replacement therapy (RRT) at diagnosis and the percentage of normal glomeruli in the biopsy were independent predictors of ESKD. The best predictor for renal recovery was the percentage of normal glomeruli, with a cut point of 10% normal glomeruli providing good stratification. A model with the predictors RRT and normal glomeruli ( N ) achieved superior discrimination for significant differences in renal survival. Dividing patients into four risk groups led to a 36-month renal survival of 96.4% (no RRT, N ≥10%), 74.0% (no RRT, N <10%), 42.3% (RRT, N ≥10%), and 14.1% (RRT, N <10%), respectively. CONCLUSIONS: These findings demonstrate that the RRS concept is transferrable to anti-GBM disease. Stratifying patients according to the need for RRT at diagnosis and renal histology improves prediction, highlighting the importance of normal glomeruli. Such stratification may assist in the management of anti-GBM disease. PODCAST: This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2023_02_27_JASN0000000000000060.mp3.


Asunto(s)
Enfermedad por Anticuerpos Antimembrana Basal Glomerular , Vasculitis Asociada a Anticuerpos Citoplasmáticos Antineutrófilos , Humanos , Estudios Retrospectivos , Estudios de Cohortes , Estudios Prospectivos , Riñón , Terapia de Reemplazo Renal , Medición de Riesgo
2.
BMJ Case Rep ; 15(11)2022 Nov 22.
Artículo en Inglés | MEDLINE | ID: mdl-36414350

RESUMEN

Balancing adequate immunosuppression with the risk of infection after renal transplantation remains a challenge. The presence of comorbidities adds to the challenge. Although infrequent, invasive fungal infections result in high morbidity and mortality risk in renal transplant recipients. This can be attributed to the intense immunosuppression in the first 6 months after renal transplantation, minimal symptomatology and the high mortality associated with fungal infections.Due to minimal available evidence, clinical judgement guides management of graft candidiasis. There is a need to develop evidence-based management guidelines for the treatment of fungal infections in renal transplants. Here, we report a case of early-onset candidiasis in a transplanted kidney and present the histological findings, multidisciplinary discussions and treatment given.


Asunto(s)
Candidiasis , Infecciones Fúngicas Invasoras , Trasplante de Riñón , Humanos , Trasplante de Riñón/efectos adversos , Receptores de Trasplantes , Candidiasis/diagnóstico , Candidiasis/tratamiento farmacológico , Terapia de Inmunosupresión
4.
Glomerular Dis ; 2(3): 139-144, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-36751668

RESUMEN

Background: IgG4-related disease (IgG4-RD) is a systemic multi-organ inflammatory disorder which affects the kidney 20% of the time. Patients with intrinsic IgG4-related kidney disease (IgG4-RKD) often have tubulointerstitial nephritis (TIN) whereas glomerular lesions like membranous nephropathy (MN) are less common. Antibodies to thrombospondin type-1 domain-containing 7A (THSD7A) have been described in primary MN, but never in association with IgG4-RKD. Case Report: We report the first case of IgG4-MN associated with THSD7A antibodies in serum and positivity on glomerular staining, in a 57-year-old Caucasian male with IgG4-RD affecting the pancreas, liver, lacrimal glands, extraocular muscles, and kidneys. This patient presented initially with glomerular disease including significant proteinuria consistent with MN. Glomerular staining for THSD7A antigen and serum THSD7A antibody titres was positive. Treatment with corticosteroids and cyclophosphamide successfully induced remission with resolution of proteinuria, and improvement in renal function. However, despite maintenance azathioprine, the patient relapsed 39 months later. On relapse, there was minimal proteinuria but a significant rise in creatinine. Subsequent renal biopsy showed less glomerular disease and instead a TIN pattern. Subsequent treatment with Rituximab and corticosteroids successfully induced remission. Conclusion: The role of THSD7A autoantibodies in MN is emerging, and as both IgG4-MN and presence of THSD7A antibody are rare occurrences in themselves, we speculate that there may be an undiscovered association between THSD7A and IgG4-MN. Routine testing for THSD7A in IgG4-MN may help to identify the link.

5.
Clin J Am Soc Nephrol ; 16(9): 1376-1386, 2021 09.
Artículo en Inglés | MEDLINE | ID: mdl-34244334

RESUMEN

BACKGROUND AND OBJECTIVES: Immune checkpoint inhibitors are increasingly used to treat various malignancies, but their application in patients with kidney transplants is complicated by high allograft rejection rates. Immune checkpoint inhibitor-associated rejection is a novel, poorly understood entity demonstrating overlapping histopathologic features with immune checkpoint inhibitor-associated acute interstitial nephritis, which poses a challenge for diagnosis and clinical management. We sought to improve the understanding of these entities through biopsy-based gene expression analysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: NanoString was used to measure and compare the expression of 725 immune-related genes in 75 archival kidney biopsies, including a 25-sample discovery cohort comprising pure T cell-mediated rejection and immune checkpoint inhibitor-associated acute interstitial nephritis and an independent 50-sample validation cohort comprising immune checkpoint inhibitor-associated acute interstitial nephritis, immune checkpoint inhibitor-associated T cell-mediated rejection, immune checkpoint inhibitor-associated crescentic GN, drug-induced acute interstitial nephritis, BK virus nephropathy, and normal biopsies. RESULTS: Significant molecular overlap was observed between immune checkpoint inhibitor-associated acute interstitial nephritis and T cell-mediated rejection. Nevertheless, IFI27, an IFN-α-induced transcript, was identified and validated as a novel biomarker for differentiating immune checkpoint inhibitor-associated T cell-mediated rejection from immune checkpoint inhibitor-associated acute interstitial nephritis (validation cohort: P<0.001, area under the receiver operating characteristic curve =100%, accuracy =86%). Principal component analysis revealed heterogeneity in inflammatory gene expression patterns within sample groups; however, immune checkpoint inhibitor-associated T cell-mediated rejection and immune checkpoint inhibitor-associated acute interstitial nephritis both demonstrated relatively more molecular overlap with drug-induced acute interstitial nephritis than T cell-mediated rejection, suggesting potential dominance of hypersensitivity mechanisms in these entities. CONCLUSIONS: These results indicate that, although there is significant molecular similarity between immune checkpoint inhibitor-associated rejection and acute interstitial nephritis, biopsy-based measurement of IFI27 gene expression represents a potential biomarker for differentiating these entities.


Asunto(s)
Perfilación de la Expresión Génica , Inhibidores de Puntos de Control Inmunológico/efectos adversos , Trasplante de Riñón , Nefritis Intersticial/inducido químicamente , Nefritis Intersticial/genética , Complicaciones Posoperatorias/inducido químicamente , Complicaciones Posoperatorias/genética , Anciano , Biopsia , Femenino , Humanos , Masculino , Persona de Mediana Edad , Nefritis Intersticial/patología , Complicaciones Posoperatorias/patología
6.
J Am Soc Nephrol ; 32(7): 1713-1732, 2021 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-34049963

RESUMEN

BACKGROUND: Accumulation of extracellular matrix in organs and tissues is a feature of both aging and disease. In the kidney, glomerulosclerosis and tubulointerstitial fibrosis accompany the decline in function, which current therapies cannot address, leading to organ failure. Although histologic and ultrastructural patterns of excess matrix form the basis of human disease classifications, a comprehensive molecular resolution of abnormal matrix is lacking. METHODS: Using mass spectrometry-based proteomics, we resolved matrix composition over age in mouse models of kidney disease. We compared the changes in mice with a global characterization of human kidneymatrix during aging and to existing kidney disease datasets to identify common molecular features. RESULTS: Ultrastructural changes in basement membranes are associated with altered cell adhesion and metabolic processes and with distinct matrix proteomes during aging and kidney disease progression in mice. Within the altered matrix, basement membrane components (laminins, type IV collagen, type XVIII collagen) were reduced and interstitial matrix proteins (collagens I, III, VI, and XV; fibrinogens; and nephronectin) were increased, a pattern also seen in human kidney aging. Indeed, this signature of matrix proteins was consistently modulated across all age and disease comparisons, and the increase in interstitial matrix was also observed in human kidney disease datasets. CONCLUSIONS: This study provides deep molecular resolution of matrix accumulation in kidney aging and disease, and identifies a common signature of proteins that provides insight into mechanisms of response to kidney injury and repair.

7.
J Am Acad Child Adolesc Psychiatry ; 60(7): 804-807, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-33711378

RESUMEN

As a socially marginalized group, LGBT youths experience elevated rates of physical and mental health problems that are leading causes of mortality due to a variety of factors. Minority stress theory links exposure to stigma with health outcome disparities. Structural stigma including biased laws, policies, and societal norms predicts approximately 20% of elevated suicidality among LGBT youths. Comprehensive public health efforts to reduce mental health disparities among LGBT youths need to address structural stigma. An interdisciplinary Health Justice approach is described, in which public health evidence is integrated with human rights principles in keeping with the bioethical Justice Imperative. In this approach, epidemiological research is used to inform public health efforts to address health disparities in LGBT youths due to structural stigma in a way that is (1) empirical; (2) aimed at basic goals of reducing morbidity and mortality; (3) applicable to diverse cultural contexts; (4) capable of amending stigma-related power and associated health inequities; and (5) guided by human rights principles. By applying human rights principles to public health needs, this approach will help to achieve health equity for LGBT youths.


Asunto(s)
Salud Pública , Minorías Sexuales y de Género , Adolescente , Derechos Humanos , Humanos , Estigma Social
8.
Am J Transplant ; 20(12): 3486-3501, 2020 12.
Artículo en Inglés | MEDLINE | ID: mdl-32372431

RESUMEN

Novel tools are needed to improve diagnostic accuracy and risk prediction in BK virus nephropathy (BKVN). We assessed the utility of intragraft gene expression testing for these purposes. Eight hundred genes were measured in 110 archival samples, including a discovery cohort of native kidney BKVN (n = 5) vs pure T cell-mediated rejection (TCMR; n = 10). Five polyomavirus genes and seven immune-related genes (five associated with BKVN and two associated with TCMR) were significantly differentially expressed between these entities (FDR < 0.05). These three sets of genes were further evaluated in samples representing a spectrum of BK infection (n = 25), followed by a multicenter validation cohort of allograft BKVN (n = 60) vs TCMR (n = 10). Polyomavirus 5-gene set expression reliably distinguished BKVN from TCMR (validation cohort AUC = 0.992), but the immune gene sets demonstrated suboptimal diagnostic performance (AUC ≤ 0.720). Within the validation cohort, no significant differences in index biopsy gene expression were identified between BKVN patients demonstrating resolution (n = 35), persistent infection (n = 14) or de novo rejection (n = 11) 6 months following a standardized reduction in immunosuppression. These results suggest that, while intragraft polyomavirus gene expression may be useful as an ancillary diagnostic for BKVN, assessment for concurrent TCMR and prediction of clinical outcome may not be feasible with current molecular tools.


Asunto(s)
Virus BK , Enfermedades Renales , Trasplante de Riñón , Infecciones por Polyomavirus , Infecciones Tumorales por Virus , Virus BK/genética , Expresión Génica , Rechazo de Injerto/etiología , Rechazo de Injerto/genética , Humanos , Riñón , Enfermedades Renales/diagnóstico , Enfermedades Renales/genética , Trasplante de Riñón/efectos adversos , Infecciones por Polyomavirus/diagnóstico , Medición de Riesgo , Linfocitos T , Infecciones Tumorales por Virus/diagnóstico
9.
Cochrane Database Syst Rev ; 10: CD012398, 2018 10 05.
Artículo en Inglés | MEDLINE | ID: mdl-30293234

RESUMEN

BACKGROUND: Schizophrenia is a severe mental health condition that is characterised by positive symptoms, such as hallucinations and delusions; negative symptoms, such as flattened affect, thought disorder (disrupted speech), and lack of motivation; and cognitive symptoms, such as problems with memory and attention. Schizophrenia can occur as an isolated episode, or as a recurring cycle of remission and relapse, and is associated with impairment in psychosocial and occupational functioning.Although antipsychotic drugs are the main treatment for people with schizophrenia, in most countries mental health services usually provide a range of add-on interventions, including occupational therapy. This is a complex intervention designed to support and enable continued participation in daily life through engagement in activities and occupations meaningful to the individual. Occupational therapists are professionals trained to deliver therapy where the emphasis is on improving occupational function and participation rather than treating symptoms, and uses a wide range of methods based on the needs of individuals. However, similar interventions may also be delivered by staff not trained as occupational therapists. OBJECTIVES: To examine the effects of occupational therapy delivered by occupational therapists compared to occupational therapy delivered by any other person for people with schizophrenia. SEARCH METHODS: We searched the Cochrane Schizophrenia Group's Study-Based Register of Trials (including trial registers) on 4 November 2016 and 26 July 2018. SELECTION CRITERIA: All randomised controlled trials evaluating the functional or clinical outcomes of occupational therapy, or both, for people with schizophrenia delivered by occupational therapists compared with occupational therapy for people with schizophrenia delivered by anyone other than occupational therapists. DATA COLLECTION AND ANALYSIS: Review authors independently inspected citations, selected studies, extracted data, and appraised study quality. MAIN RESULTS: The search yielded 1633 records. Of these, we retrieved 17 full-text reports (14 studies) for further scrutiny, which we subsequently excluded as they did not meet our inclusion criteria. AUTHORS' CONCLUSIONS: Currently there are no randomised controlled trials comparing delivery of occupational therapy for people diagnosed with schizophrenia by occupational therapists with delivery of similar interventions by anyone other than occupational therapists. Research studies employing methodologically robust trial designs are needed to establish whether or not there are better outcomes for people with a diagnosis of schizophrenia with occupational therapy that is delivered by trained occupational therapists.


Asunto(s)
Terapeutas Ocupacionales , Terapia Ocupacional/métodos , Esquizofrenia/terapia , Especialización , Humanos
10.
Science ; 353(6294): 7, 2016 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-27352839
11.
Behav Cogn Psychother ; 44(1): 92-103, 2016 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-25597777

RESUMEN

BACKGROUND: Research has implicated causal, mediating and meaningful roles for mental imagery in the experience of psychological distress, including self-injury. AIMS: The present study aimed to further the understanding of this relationship through exploring the lived experiences of mental imagery from the perspective of those who self-injure. METHOD: This study employed an inductive qualitative design using semi-structured interviews and Interpretative Phenomenological Analysis (IPA). Ten participants were recruited from universities in North West England. RESULTS: Three main themes were identified from the analysis: (i) The origins and precipitants of self-injurious imagery; (ii) What it is like to experience self-injurious imagery; and (iii) The meaning and interpretation of self-injurious imagery. CONCLUSIONS: The study findings indicate that mental imagery is an important experience for those who self-injure. Clinical and research implications of the findings are discussed.


Asunto(s)
Conducta Autodestructiva/psicología , Conducta Autodestructiva/terapia , Adaptación Psicológica , Adulto , Estudios de Casos y Controles , Emociones , Femenino , Humanos , Entrevista Psicológica/métodos , Acontecimientos que Cambian la Vida , Masculino , Investigación Cualitativa , Autoimagen
12.
Psychiatry Res ; 228(3): 626-32, 2015 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-26099655

RESUMEN

Childhood trauma (CT) and psychosis may be associated. Drawing on the dissociation and social psychological literature, the current study examined the mediating role of structural aspects of self in explaining the relationship between childhood trauma and psychosis. Twenty-nine individuals with psychosis were compared with 31 healthy volunteers regarding childhood trauma, dissociation and self-concept clarity (SCC). High rates of maltreatment were found in the psychosis sample. Additionally, clinical participants reported more dissociation and less self-concept clarity. Mediational analyses were carried out on pooled data from across both clinical and non-clinical samples. These suggested that the influence of physical neglect in increasing the likelihood of experiencing psychosis was explicable through the effects of increased dissociation. Self-concept clarity mediated the relationship between psychosis and total childhood trauma, emotional abuse, physical abuse, emotional and physical neglect. Furthermore, dissociation and self-concept clarity were strongly correlated providing evidence that they may form a unitary underlying concept of 'self-concept integration'. The study provides further evidence of the link between childhood trauma and psychosis. Self-concept integration may be adversely affected by negative childhood experiences, which increases psychosis risk. Methodological limitations, clinical implications and suggestions for future research are considered.


Asunto(s)
Trastornos Disociativos/psicología , Trastornos Psicóticos/psicología , Autoimagen , Trastornos por Estrés Postraumático/psicología , Adolescente , Adulto , Niño , Maltrato a los Niños/psicología , Femenino , Humanos , Masculino , Factores de Riesgo , Estadística como Asunto , Encuestas y Cuestionarios , Adulto Joven
13.
Early Interv Psychiatry ; 9(3): 185-99, 2015 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24958353

RESUMEN

AIM: Family members often play a vital role in seeking help for loved ones experiencing first-episode psychosis. Understanding this experience is crucial in facilitating the help-seeking process. Qualitative research offers valuable insight into the lived experience of family members who seek help on behalf of a loved one experiencing first-episode psychosis. METHOD: The current research presents a systematic review of qualitative studies exploring the family member experience of seeking help for first-episode psychosis. RESULTS: A meta-synthesis of 13 qualitative studies has revealed four themes relating to family members' experience of seeking help for first-episode psychosis. These include a sense of not knowing, the reaching of crisis point, the impact upon the family member and the mediating role of interactions with others. A further synthesis of translation captures the interaction of these themes within this experience. CONCLUSIONS: The findings provide a novel insight into this experience, suggesting implications for clinical practice. These include a focus upon the facilitation of early positive interactions with family members and for first-episode psychosis to be presented to families in a normalizing manner. The need for future research that examines the experience of those who do not seek help from health services is discussed.


Asunto(s)
Familia/psicología , Aceptación de la Atención de Salud/psicología , Trastornos Psicóticos/psicología , Humanos , Investigación Cualitativa
14.
PLoS One ; 8(10): e78844, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24205330

RESUMEN

BACKGROUND: Pervasive negative thoughts about the self are central to the experience of depression. Brain imaging studies in the general population have localised self-related cognitive processing to areas of the medial pre-frontal cortex. AIMS: To use fMRI to compare the neural correlates of self-referential processing in depressed and non-depressed participants. METHOD: Cross-sectional comparison of regional activation using Blood Oxygen Level Dependent (BOLD) fMRI in 13 non-medicated participants with major depressive episode and 14 comparison participants, whilst carrying out a self-referential cognitive task. RESULTS: Both groups showed significant activation of the dorsomedial pre-frontal cortex and posterior cingulate cortex in the 'self-referent' condition. The depressed group showed significantly greater activation in the medial superior frontal cortex during the self-referent task. No difference was observed between groups in the 'other-referent' condition. CONCLUSIONS: Major depressive episode is associated with specific neurofunctional changes related to self-referential processing.


Asunto(s)
Encéfalo/fisiopatología , Cognición , Trastorno Depresivo Mayor/fisiopatología , Trastorno Depresivo Mayor/psicología , Imagen por Resonancia Magnética , Autoimagen , Adulto , Conducta/fisiología , Humanos
15.
Early Interv Psychiatry ; 7(3): 291-9, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-22741743

RESUMEN

AIM: Relatives of service users involved with Early Intervention in Psychosis services often experience substantial distress and need associated with their role as caregivers. This study adapted versions of the relatives cardinal needs schedule and the Texas inventory of grief and tested their utility for use among relatives of service users experiencing a first episode of psychosis. METHODS: staff, service users and relatives were consulted and a pilot took place which facilitated the creation of the relatives' urgent needs schedule-early Intervention version (RUNS-EI) and the Texas inventory of grief-early Intervention version (TIG-EI). Thirty service user-caregiver dyads were recruited for the evaluation of reliability and validity. RESULTS: The level of 'urgent need' identified by the RUNS-EI demonstrated good concurrent validity with measures of service user social and global functioning as well as measures assessing relatives' distress, expressed emotion and grief. The measure demonstrated acceptable interrater and test-retest reliability. The profile of need is reported. The TIG-EI demonstrated 'excellent' internal consistency. It also demonstrated good concurrent validity with increased TIG-EI scores correlated with reduced service user social and global functioning as well as increased scores on measures assessing relatives' distress, expressed emotion and caregiving needs. CONCLUSIONS: Results appear to support these assessments' utility as measures of need for psychosocial intervention and grief among relatives supporting service users experiencing a first episode of psychosis.


Asunto(s)
Cuidadores/psicología , Pesar , Evaluación de Necesidades , Trastornos Psicóticos/enfermería , Estrés Psicológico/psicología , Adulto , Anciano , Costo de Enfermedad , Estudios Transversales , Emoción Expresada , Femenino , Humanos , Masculino , Persona de Mediana Edad , Escalas de Valoración Psiquiátrica , Trastornos Psicóticos/diagnóstico , Reproducibilidad de los Resultados , Estrés Psicológico/diagnóstico
16.
PLoS One ; 7(3): e31824, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-22427809

RESUMEN

The need for policy makers to understand science and for scientists to understand policy processes is widely recognised. However, the science-policy relationship is sometimes difficult and occasionally dysfunctional; it is also increasingly visible, because it must deal with contentious issues, or itself becomes a matter of public controversy, or both. We suggest that identifying key unanswered questions on the relationship between science and policy will catalyse and focus research in this field. To identify these questions, a collaborative procedure was employed with 52 participants selected to cover a wide range of experience in both science and policy, including people from government, non-governmental organisations, academia and industry. These participants consulted with colleagues and submitted 239 questions. An initial round of voting was followed by a workshop in which 40 of the most important questions were identified by further discussion and voting. The resulting list includes questions about the effectiveness of science-based decision-making structures; the nature and legitimacy of expertise; the consequences of changes such as increasing transparency; choices among different sources of evidence; the implications of new means of characterising and representing uncertainties; and ways in which policy and political processes affect what counts as authoritative evidence. We expect this exercise to identify important theoretical questions and to help improve the mutual understanding and effectiveness of those working at the interface of science and policy.


Asunto(s)
Comunicación Interdisciplinaria , Política Pública/tendencias , Proyectos de Investigación , Toma de Decisiones en la Organización , Inglaterra
17.
Biochim Biophys Acta ; 1787(2): 113-20, 2009 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-19081388

RESUMEN

The fumarate reductases from S. frigidimarina NCIMB400 and S. oneidensis MR-1 are soluble and monomeric enzymes located in the periplasm of these bacteria. These proteins display two redox active domains, one containing four c-type hemes and another containing FAD at the catalytic site. This arrangement of single-electron redox co-factors leading to multiple-electron active sites is widespread in respiratory enzymes. To investigate the properties that allow a chain of single-electron co-factors to sustain the activity of a multi-electron catalytic site, redox titrations followed by NMR and visible spectroscopies were applied to determine the microscopic thermodynamic parameters of the hemes. The results show that the redox behaviour of these fumarate reductases is similar and dominated by a strong interaction between hemes II and III. This interaction facilitates a sequential transfer of two electrons from the heme domain to FAD via heme IV.


Asunto(s)
Grupo Citocromo c/metabolismo , Hemo/química , Shewanella/enzimología , Succinato Deshidrogenasa/química , Succinato Deshidrogenasa/metabolismo , Dominio Catalítico , Grupo Citocromo c/química , Electrones , Hemo/metabolismo , Concentración de Iones de Hidrógeno , Cinética , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Oxidación-Reducción , Unión Proteica , Shewanella/química , Shewanella/metabolismo , Solubilidad , Termodinámica
18.
Biochemistry ; 47(46): 11973-80, 2008 Nov 18.
Artículo en Inglés | MEDLINE | ID: mdl-18950243

RESUMEN

The bacteria belonging to the genus Shewanella are facultative anaerobes that utilize a variety of terminal electron acceptors which includes soluble and insoluble metal oxides. The tetraheme c-type cytochrome isolated during anaerobic growth of Shewanella frigidimarina NCIMB400 ( Sfc) contains 86 residues and is involved in the Fe(III) reduction pathways. Although the functional properties of Sfc redox centers are quite well described, no structures are available for this protein. In this work, we report the solution structure of the reduced form of Sfc. The overall fold is completely different from those of the tetraheme cytochromes c 3 and instead has similarities with the tetraheme cytochrome recently isolated from Shewanella oneidensis ( Soc). Comparison of the tetraheme cytochromes from Shewanella shows a considerable diversity in their primary structure and heme reduction potentials, yet they have highly conserved heme geometry, as is the case for the family of tetraheme cytochromes isolated from Desulfovibrio spp.


Asunto(s)
Proteínas Bacterianas/química , Citocromos c/química , Pliegue de Proteína , Shewanella/enzimología , Secuencias de Aminoácidos/fisiología , Proteínas Bacterianas/metabolismo , Citocromos c/metabolismo , Desulfovibrio/enzimología , Hemo/química , Hemo/metabolismo , Hierro/química , Hierro/metabolismo , Oxidación-Reducción , Óxidos/química , Óxidos/metabolismo , Especificidad de la Especie
19.
Biochem Soc Trans ; 36(Pt 5): 992-5, 2008 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-18793176

RESUMEN

Rhodobacter sphaeroides produces a novel cytochrome, designated as SHP (sphaeroides haem protein), that is unusual in having asparagine as a redox-labile haem ligand. The gene encoding SHP is contained within an operon that also encodes a DHC (dihaem cytochrome c) and a membrane-associated cytochrome b. DHC and SHP have been shown to have high affinity for each other at low ionic strength (Kd=0.2 microM), and DHC is able to reduce SHP very rapidly. The reduced form of the protein, SHP2+ (reduced or ferrous SHP), has high affinity for both oxygen and nitric oxide (NO). It has been shown that the oxyferrous form, SHP2+-O2 (oxygen-bound form of SHP), reacts rapidly with NO to produce nitrate, whereas SHP2+-NO (the NO-bound form of SHP) will react with superoxide with the same product formed. It is therefore possible that SHP functions physiologically as a nitric oxide dioxygenase, protecting the organism against NO poisoning, and we propose a possible mechanism for this process.


Asunto(s)
Hemoproteínas/metabolismo , Oxigenasas/metabolismo , Rhodobacter sphaeroides/química , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Grupo Citocromo c/química , Grupo Citocromo c/metabolismo , Hemoproteínas/química , Modelos Moleculares , Estructura Molecular , Nitratos/metabolismo , Óxido Nítrico/metabolismo , Oxígeno/metabolismo , Oxigenasas/química , Estructura Terciaria de Proteína , Rhodobacter sphaeroides/enzimología , Superóxidos/metabolismo
20.
FEBS Lett ; 581(20): 3805-8, 2007 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-17659281

RESUMEN

A c-type cytochrome from Shewanella oneidensis MR-1, containing eight hemes, has been previously designated as an octaheme tetrathionate reductase (OTR). The structure of OTR revealed that the active site contains an unusual lysine-ligated heme, despite the presence of a CXXCH motif in the sequence that would predict histidine ligation. This lysine ligation has been previously observed only in the pentaheme nitrite reductases, suggesting that OTR may have a possible role in nitrite reduction. We have now shown that OTR is an efficient nitrite and hydroxylamine reductase and that ammonium ion is the product. These results indicate that OTR may have a role in the biological nitrogen cycle.


Asunto(s)
Citocromos c1/metabolismo , Hemo/química , Hidroxilamina/metabolismo , Nitritos/metabolismo , Shewanella/enzimología , Sitios de Unión , Catálisis , Citocromos c1/química , Cinética , Modelos Moleculares , Oxidación-Reducción , Especificidad por Sustrato
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