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1.
Nature ; 450(7169): 560-5, 2007 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-18033299

RESUMO

From the standpoints of both basic research and biotechnology, there is considerable interest in reaching a clearer understanding of the diversity of biological mechanisms employed during lignocellulose degradation. Globally, termites are an extremely successful group of wood-degrading organisms and are therefore important both for their roles in carbon turnover in the environment and as potential sources of biochemical catalysts for efforts aimed at converting wood into biofuels. Only recently have data supported any direct role for the symbiotic bacteria in the gut of the termite in cellulose and xylan hydrolysis. Here we use a metagenomic analysis of the bacterial community resident in the hindgut paunch of a wood-feeding 'higher' Nasutitermes species (which do not contain cellulose-fermenting protozoa) to show the presence of a large, diverse set of bacterial genes for cellulose and xylan hydrolysis. Many of these genes were expressed in vivo or had cellulase activity in vitro, and further analyses implicate spirochete and fibrobacter species in gut lignocellulose degradation. New insights into other important symbiotic functions including H2 metabolism, CO2-reductive acetogenesis and N2 fixation are also provided by this first system-wide gene analysis of a microbial community specialized towards plant lignocellulose degradation. Our results underscore how complex even a 1-microl environment can be.


Assuntos
Bactérias/metabolismo , Genoma Bacteriano/genética , Genômica , Intestinos/microbiologia , Isópteros/metabolismo , Isópteros/microbiologia , Madeira/metabolismo , Animais , Bactérias/enzimologia , Bactérias/genética , Bactérias/isolamento & purificação , Fontes de Energia Bioelétrica , Carbono/metabolismo , Domínio Catalítico , Celulose/metabolismo , Costa Rica , Genes Bacterianos/genética , Glicosídeo Hidrolases/química , Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Hidrólise , Lignina/metabolismo , Modelos Biológicos , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Simbiose , Madeira/química , Xilanos/metabolismo
2.
Structure ; 12(3): 487-94, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15016364

RESUMO

AvrB is a Pseudomonas syringae type III effector protein that is translocated into host plant cells during attempted pathogenesis. Arabidopsis harboring the corresponding resistance protein RPM1 can detect AvrB and mount a rapid host defense response, thus avoiding active infection. In the plant cell, AvrB induces phosphorylation of RIN4, a key component in AvrB/RPM1 recognition. Although the AvrB/RPM1 system is among the best characterized of the numerous bacterial effector/plant resistance protein systems involved in plant disease resistance and pathogenesis, the details of the molecular recognition mechanism are still unclear. To gain further insights, the crystal structure of AvrB was determined. The 2.2 A structure exhibits a novel mixed alpha/beta bilobal fold. Aided by the structural information, we demonstrate that one lobe is the determinant of AvrB/RPM1 recognition specificity. This structural information and preliminary structure-function studies provide a framework for the future understanding of AvrB function on the molecular level.


Assuntos
Proteínas de Bactérias/química , Sequência de Aminoácidos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cristalografia por Raios X , Modelos Moleculares , Dados de Sequência Molecular , Dobramento de Proteína , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Pseudomonas syringae/química , Pseudomonas syringae/genética , Pseudomonas syringae/metabolismo , Alinhamento de Sequência
3.
Eur Psychiatry ; 18(6): 285-9, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14611923

RESUMO

PURPOSE: Restriction in involuntary hospital admission and reduced lengths of inpatient stay increase burden on relatives of individuals with schizophrenia. This study aims at assessing the relationship between caregiver burden and behavioural disturbances of the affected, e.g. threats, nuisances, but also substance use and aggression. Two weeks before the last hospitalisation of the affected are considered as being the most burdensome period for relatives. SUBJECTS AND METHODS: Sixty-four relatives of schizophrenic patients were assessed by the semi-structured "Interview for Measuring the Burden on the Family". Subscales and total scales of burden were calculated. Predictors were identified by regression analyses. RESULTS: The most important predictor of burden is burden in the relationship between caregiver and the affected representing the changes in the relationship occurring in acute illness. Threats, nuisances, time spent with the affected, and burden due to restricted social life and leisure activities were additional predictors, but not aggression or substance abuse. Eighty-five percent of the cases could be assigned correctly. DISCUSSION AND CONCLUSIONS: To better encounter burden, relatives should learn to cope with disturbing behaviour of and altered relationship to the affected, but also with their own needs. Finally, relatives must be included in the decision whether or not an affected person should be hospitalised.


Assuntos
Cuidadores/psicologia , Efeitos Psicossociais da Doença , Esquizofrenia/diagnóstico , Psicologia do Esquizofrênico , Adaptação Psicológica , Adulto , Idoso , Agressão/psicologia , Relações Familiares , Feminino , Hospitalização , Humanos , Entrevista Psicológica , Atividades de Lazer , Masculino , Pessoa de Meia-Idade , Fatores de Risco , Comportamento Social , Transtornos Relacionados ao Uso de Substâncias/diagnóstico , Transtornos Relacionados ao Uso de Substâncias/psicologia , Suíça
4.
J Biol Chem ; 283(33): 22557-64, 2008 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-18515360

RESUMO

Understanding the structural basis for protein thermostability is of considerable biological and biotechnological importance as exemplified by the industrial use of xylanases at elevated temperatures in the paper pulp and animal feed sectors. Here we have used directed protein evolution to generate hyperthermostable variants of a thermophilic GH11 xylanase, EvXyn11. The Gene Site Saturation Mutagenesis (GSSM) methodology employed assesses the influence on thermostability of all possible amino acid substitutions at each position in the primary structure of the target protein. The 15 most thermostable mutants, which generally clustered in the N-terminal region of the enzyme, had melting temperatures (Tm) 1-8 degrees C higher than the parent protein. Screening of a combinatorial library of the single mutants identified a hyperthermostable variant, EvXyn11TS, containing seven mutations. EvXyn11TS had a Tm approximately 25 degrees C higher than the parent enzyme while displaying catalytic properties that were similar to EvXyn11. The crystal structures of EvXyn11 and EvXyn11TS revealed an absence of substantial changes to identifiable intramolecular interactions. The only explicable mutations are T13F, which increases hydrophobic interactions, and S9P that apparently locks the conformation of a surface loop. This report shows that the molecular basis for the increased thermostability is extraordinarily subtle and points to the requirement for new tools to interrogate protein folding at non-ambient temperatures.


Assuntos
Endo-1,4-beta-Xilanases/química , Engenharia de Proteínas/métodos , Códon , Primers do DNA , Estabilidade de Medicamentos , Endo-1,4-beta-Xilanases/genética , Biblioteca Gênica , Reação em Cadeia da Polimerase , Termodinâmica
5.
Appl Microbiol Biotechnol ; 74(1): 113-24, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17103163

RESUMO

A unique multifunctional glycosyl hydrolase was discovered by screening an environmental DNA library prepared from a microbial consortium collected from cow rumen. The protein consists of two adjacent catalytic domains. Sequence analysis predicted that one domain conforms to glycosyl hydrolase family 5 and the other to family 26. The enzyme is active on several different beta-linked substrates and possesses mannanase, xylanase, and glucanase activities. Site-directed mutagenesis studies on the catalytic residues confirmed the presence of two functionally independent catalytic domains. Using site-specific mutations, it was shown that one catalytic site hydrolyzes beta-1,4-linked mannan substrates, while the second catalytic site hydrolyzes beta-1,4-linked xylan and beta-1,4-linked glucan substrates. Polysaccharide Analysis using Carbohydrate gel Electrophoresis (PACE) also confirmed that the enzyme has discrete domains for binding and hydrolysis of glucan- and mannan-linked polysaccharides. Such multifunctional enzymes have many potential industrial applications in plant processing, including biomass saccharification, animal feed nutritional enhancement, textile, and pulp and paper processing.


Assuntos
Glicosídeo Hidrolases , Complexos Multienzimáticos , Rúmen/microbiologia , Animais , Sequência de Bases , Bovinos , Biblioteca Gênica , Glucanos/metabolismo , Glicosídeo Hidrolases/química , Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Microbiologia Industrial , Mananas/metabolismo , Dados de Sequência Molecular , Complexos Multienzimáticos/química , Complexos Multienzimáticos/genética , Complexos Multienzimáticos/metabolismo , Mutagênese Sítio-Dirigida , Análise de Sequência de DNA , Xilanos/metabolismo
6.
J Biol Chem ; 280(10): 9431-8, 2005 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-15618218

RESUMO

There is a growing need in the textile industry for more economical and environmentally responsible approaches to improve the scouring process as part of the pretreatment of cotton fabric. Enzymatic methods using pectin-degrading enzymes are potentially valuable candidates in this effort because they could reduce the amount of toxic alkaline chemicals currently used. Using high throughput screening of complex environmental DNA libraries more than 40 novel microbial pectate lyases were discovered, and their enzymatic properties were characterized. Several candidate enzymes were found that possessed pH optima and specific activities on pectic material in cotton fibers compatible with their use in the scouring process. However, none exhibited the desired temperature characteristics. Therefore, a candidate enzyme was selected for evolution. Using Gene Site Saturation Mutagenesistrade mark technology, 36 single site mutants exhibiting improved thermotolerance were produced. A combinatorial library derived from the 12 best performing single site mutants was then generated by using Gene Reassemblytrade mark technology. Nineteen variants with further improved thermotolerance were produced. These variants were tested for both improved thermotolerance and performance in the bioscouring application. The best performing variant (CO14) contained eight mutations and had a melting temperature 16 degrees C higher than the wild type enzyme while retaining the same specific activity at 50 degrees C. Optimal temperature of the evolved enzyme was 70 degrees C, which is 20 degrees C higher than the wild type. Scouring results obtained with the evolved enzyme were significantly better than the results obtained with chemical scouring, making it possible to replace the conventional and environmentally harmful chemical scouring process.


Assuntos
Fibra de Algodão , Polissacarídeo-Liases/metabolismo , Bactérias/classificação , Bactérias/enzimologia , Evolução Molecular Direcionada , Biblioteca Gênica , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Filogenia , Polissacarídeo-Liases/química , Polissacarídeo-Liases/genética , Conformação Proteica , Proteínas Recombinantes/metabolismo
7.
Plant Mol Biol ; 53(3): 273-9, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14750518

RESUMO

Yeast two-hybrid assays were used to identify rice proteins interacting with two rice cyclins and other proteins potentially involved in cell cycling. The DNA sequences encoding 119 protein fragments identified were then compared by BLAST against proteins in GenBank. The proteins found include myosin-like proteins, transcription factors, kinesins, centromere proteins and undefined proteins. Based on interactions with cyclins and other elements required for cycling, we believe the undefined proteins may be involved in associated cycling processes. The identification of proteins involved in cell cycle regulation in rice may allow for the control of agronomic traits involving plant growth or development.


Assuntos
Ciclo Celular/fisiologia , Ciclinas/metabolismo , Oryza/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ciclo Celular/genética , Ciclinas/genética , DNA Complementar/química , DNA Complementar/genética , Dados de Sequência Molecular , Ligação Proteica , Saccharomyces cerevisiae/genética , Análise de Sequência de DNA , Técnicas do Sistema de Duplo-Híbrido
8.
Proc Natl Acad Sci U S A ; 100(8): 4945-50, 2003 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-12684538

RESUMO

We used a systematic approach to build a network of genes associated with developmental and stress responses in rice by identifying interaction domains for 200 proteins from stressed and developing tissues, by measuring the associated gene expression changes in different tissues exposed to a variety of environmental, biological, and chemical stress treatments, and by localizing the cognate genes to regions of stress-tolerance trait genetic loci. The integrated data set suggests that similar genes respond to environmental cues and stresses, and some may also regulate development. We demonstrate that the data can be used to correctly predict gene function in monocots and dicots. As a result, we have identified five genes that contribute to disease resistance in Arabidopsis.


Assuntos
Genes de Plantas , Oryza/genética , Proteínas 14-3-3 , Arabidopsis/genética , DNA de Plantas/genética , Expressão Gênica , Dados de Sequência Molecular , Oryza/crescimento & desenvolvimento , Oryza/metabolismo , Fenótipo , Fosfoproteínas Fosfatases/química , Fosfoproteínas Fosfatases/genética , Fosfoproteínas Fosfatases/metabolismo , Doenças das Plantas/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Subunidades Proteicas , Locos de Características Quantitativas , Sementes/crescimento & desenvolvimento , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Técnicas do Sistema de Duplo-Híbrido , Tirosina 3-Mono-Oxigenase/genética , Tirosina 3-Mono-Oxigenase/metabolismo
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