In HspA from Helicobacter pylori vicinal disulfide bridges are a key determinant of domain B structure

Helicobacter pylori produces a heat shock protein A (HspA) that is unique to this bacteria. While the first 91 residues (domain A) of the protein are similar to GroES, the last 26 (domain B) are unique to HspA. Domain B contains eight histidines and four cysteines and was suggested to bind nickel. We have produced HspA and two mutants: Cys94Ala and Cys94Ala/Cys111Ala and identified the disulfide bridge pattern of the protein. We found that the cysteines are engaged in three disulfide bonds: Cys51/Cys53, Cys94/Cys111 and Cys95/Cys112 that result in a unique closed loop structure for the domain

Representações Escolares e Livros Didáticos: Construindo um Perfil com Ênfase no Cotidiano

Com o foco no ensino de química, este trabalho aplica a ferramenta teórica das representações escolares na análise dos conceitos de reação química presentes em livros didáticos da Escola Básica e da Escola Superior concernentes a essa disciplina. Após situar inicialmente o campo de discussões dasrepresentações escolares, suas ideias e proposições utilizadas, desenvolve-se uma breve evidenciação das aproximações e distanciamentos entre os livros analisados e, com base nas suas possíveis relações, traz-se em seguida a constituição de um perfil de representações escolares que organizarepresentações aproximáveis na produção de um conhecimento químico escolar. Através dessa abordagem, ratificam-se diversas formas de conhecimento produzidas no lócus escolar e diferenciadas de outros universos possíveis que através da ferramenta teórica das representações escolares se fazemvisibilizadas

MTERF factors: a multifunction protein family

The MTERF family is a large protein family, identified in metazoans and plants, which consists of four subfamilies, MTERF1, 2, 3 and 4. Mitochondrial localisation was predicted for the vast majority of MTERF family members and demonstrated for the characterised MTERF proteins. The main structural feature of MTERF proteins is the presence of a modular architecture, based on repetitions of a 30-residue module, the mTERF motif, containing leucine zipperlike heptads. The MTERF family includes transcription termination factors: human mTERF, sea urchin mtDBP and Drosophila DmTTF. In addition to terminating transcription, they are involved in transcription initiation and in the control of mtDNA replication. This multiplicity of functions seems to flank differences in the gene organisation of mitochondrial genomes. MTERF2 and MTERF3 play antithetical roles in controlling mitochondrial transcription: that is, mammalian and Drosophila MTERF3 act as negative regulators, whereas mammalian MTERF2 functions as a positive regulator. Both proteins contact mtDNA in the promoter region, perhaps establishing interactions, either mutual or with other factors. Regulation of MTERF gene expression in human and Drosophila depends on nuclear transcription factors NRF-2 and DREF, respectively, and proceeds through pathways which appear to discriminate between factors positively or negatively acting in mitochondrial transcription. In this emerging scenario, it appears that MTERF proteins act to coordinate mitochondrial transcription

O ensino superior e o mercado de trabalho

Este ensaio reproduz parte das opiniões expressas no artigo "Employment and Work of British and German Graduates", da autoria de John Brennan, Stina Lyon, Harald Schomburg e Ulrich Teichler (1) sobre a influência do ensino no percurso profissional dos diplomados. Foram tidos em conta outras abordagens à mesma problemática, como a de Christopher Jenks no seu livro "Inequality" (2) e a experiência pessoal do autor

Three-dimensional structure of human cyclooxygenase (hCOX)-1

The beneficial effects of Cyclooxygenases (COX) inhibitors on human health have been known for thousands of years. Nevertheless, COXs, particularly COX-1, have been linked to a plethora of human diseases such as cancer, heart failure, neurological and neurodegenerative diseases only recently. COXs catalyze the first step in the biosynthesis of prostaglandins (PGs) and are among the most important mediators of inflammation. All published structural work on COX-1 deals with the ovine isoenzyme, which is easier to produce in milligram-quantities than the human enzyme and crystallizes readily. Here, we report the long-sought structure of the human cyclooxygenase-1 (hCOX-1) that we refined to an R/Rfree of 20.82/26.37, at 3.36 Å resolution. hCOX-1 structure provides a detailed picture of the enzyme active site and the residues crucial for inhibitor/substrate binding and catalytic activity. We compared hCOX-1 crystal structure with the ovine COX-1 and human COX-2 structures by using metrics based on Cartesian coordinates, backbone dihedral angles, and solvent accessibility coupled with multivariate methods. Differences and similarities among structures are discussed, with emphasis on the motifs responsible for the diversification of the various enzymes (primary structure, stability, catalytic activity, and specificity). The structure of hCOX-1 represents an essential step towards the development of new and more selective COX-1 inhibitors of enhanced therapeutic potential