We become more aware of the void as we explore it

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Computational and Statistical Analyses of Amino Acid Usage and Physico-Chemical Properties of the Twelve Late Embryogenesis Abundant Protein Classes

Late Embryogenesis Abundant Proteins (LEAPs) are ubiquitous proteins expected to play major roles in desiccation tolerance. Little is known about their structure - function relationships because of the scarcity of 3-D structures for LEAPs. The previous building of LEAPdb, a database dedicated to LEAPs from plants and other organisms, led to the classification of 710 LEAPs into 12 non-overlapping classes with distinct properties. Using this resource, numerous physico-chemical properties of LEAPs and amino acid usage by LEAPs have been computed and statistically analyzed, revealing distinctive features for each class. This unprecedented analysis allowed a rigorous characterization of the 12 LEAP classes, which differed also in multiple structural and physico-chemical features. Although most LEAPs can be predicted as intrinsically disordered proteins, the analysis indicates that LEAP class 7 (PF03168) and probably LEAP class 11 (PF04927) are natively folded proteins. This study thus provides a detailed description of the structural properties of this protein family opening the path toward further LEAP structure - function analysis. Finally, since each LEAP class can be clearly characterized by a unique set of physico-chemical properties, this will allow development of software to predict proteins as LEAPs

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Identification et caractérisation moléculaire d'une protéine LEA (Late Embryogenesis Abundant) mitochondriale exprimée dans les semences de pois

Les protéines LEA (Late Embryogenesis Abundant) forment une large famille de protéines hydrophiles et thermorésistantes qui possèdent des motifs répétés. Elles s'accumulent au cours de la maturation de la graine et disparaissent pendant la germination. De nombreuses protéines LEA sont aussi exprimées dans les tissus végétatifs en réponse à l'ABA et à différents stress. Toutes ces caractéristiques suggèrent que les protéines LEA soient impliquées dans la tolérance à la dessiccation. Elles ont été identifiées dans de nombreux compartiments sub-cellulaires: noyau, chloroplaste, cytosol, reticulum endoplasmique, appareil de Golgi... Mais aucune n'a encore été décrite dans les mitochondries. Au cours de l'étude du protéome mitochondrial des graines de pois, une protéine avait montré des similarités de séquences avec une protéine LEA-like de soja (Bardel et al., 2002). L'ADNc codant cette protéine (PsLEAm) a été cloné, révélant la présence d'une pré-séquence d'adressage mitochondrial. Des expériences de fractionnement sub-mitochondrial ainsi que l'expression transitoire d'une protéine de fusion avec la GFP ont permis de démontrer que PsLEAm était localisée dans la matrice mitochondriale. PsLEAm possède toutes les caractéristiques de la famille des LEA: stabilité à la chaleur, forte hydrophilicité, présence de motifs répétés et accumulation en fin de maturation. L'application d'ABA exogène durant l'imbibition de la graine ou un stress hydrique sévère des plantes développées réinduisent l'expression de PsLEAm. Une protéine PsLEAm mature recombinante a été surexprimée chez Escherichia coli puis partiellement purifiée. Dans un test in vitro, cette protéine est apparue capable de protéger deux enzymes de la matrice mitochondriale, la fumarase et la rhodanèse, lors d'une dessiccation totale. L'analyse ultérieure de la structure et de la fonction de PsLEAm permettront d'élucider l'implication de PsLEAm dans la protection des mitochondries au cours de la maturation.LEA (Late Embryogenesis Abundant) proteins belong to a large hydrophilic heat-resistant family, and exhibit repeated motifs in their sequence. The LEA proteins accumulate during seed maturation and disappear upon germination. A number of LEA proteins have been shown to also accumulate in plant tissues in response to ABA and numerous stresses. All the above characteristics support the idea that LEA proteins are involved in desiccation tolerance. They were found in many sub-cellular compartments: nucleus, chloroplasts, cytosol, endoplasmique reticulum, Golgi apparatus... But no LEA protein has been described in mitochondria so far. In a survey of pea mitochondrial proteome, a putative seed mitochondrial protein exhibited peptide tag sequence similarities with a soybean LEA-like protein (Bardel et al, 2002). The cDNA encoded this protein (PsLEAm) was cloned and revealed a typical amino-terminal transit peptide in the protein sequence. Biochemical evidence and GFP reporter transient expression in protoplast indicated that PsLEAm was localized in mitochondria matrix space. PsLEAm exhibited most of the LEA family features: heat solubility, high hydrophilicity, repeated motives and accumulation during late maturation. Moreover, exogenous ABA application during seed imbibition and severe water stress in mature plants re-induced PsLEAm expression. To explore the function of PsLEAm in mitochondria, a recombinant mature PsLEAm was overexpressed in Escherichia coli and was then partially purified. The recombinant protein was shown to protect two mitochondrial matrix enzymes, fumarase and rhodanese, during drying in an in vitro assay. Our future efforts will be focused on structural and functional analyses of PsLEAm, which will be a step forward to understanding the protective role that PsLEAm during seed maturation.ANGERS-BU Lettres et Sciences (490072106) / SudocSudocFranceF