Dihydroorotate dehydrogenase (DHODH) catalyzes the oxidation of dihydroorotate to orotate during the fourth step of the de novo pyrimidine synthesis pathway. In rapidly proliferating mammalian cells, pyrimidine salvage pathway is insufficient to overcome deficiencies in that pathway for nucleotide synthesis. Moreover, as certain parasites lack salvage enzymes, relying solely on the de novo pathway, DHODH inhibition has turned out as an efficient way to block pyrimidine biosynthesis. Escherichia coli DHODH (EcDHODH) is a class 2 DHODH, found associated to cytosolic membranes through an N-terminal extension. We used electronic spin resonance (ESR) to study the interaction of EcDHODH with vesicles of 1,2-dioleoyl-sn-glycero-phosphatidylcholine/detergent. Changes in vesicle dynamic structure induced by the enzyme were monitored via spin labels located at different positions of phospholipid derivatives. Two-component ESR spectra are obtained for labels 5- and 10-phosphatidylcholine in presence of EcDHODH, whereas other probes show a single-component spectrum. The appearance of an additional spectral component with features related to fast-motion regime of the probe is attributed to the formation of a defect-like structure in the membrane hydrophobic region. This is probably the mechanism used by the protein to capture quinones used as electron acceptors during catalysis. The use of specific spectral simulation routines allows us to characterize the ESR spectra in terms of changes in polarity and mobility around the spin-labeled phospholipids. We believe this is the first report of direct evidences concerning the binding of class 2 DHODH to membrane systems.
Dihydroorotate dehydrogenases (DHODHs) are enzymes that catalyze the fourth step of the de novo synthesis of pyrimidine nucleotides. In this reaction, DHODH converts dihydroorotate to orotate, using a flavine mononucleotide as a cofactor. Since the synthesis of nucleotides has different pathways in mammals as compared to parasites, DHODH has gained much attention as a promising target for drug design. Escherichia coli DHODH (EcDHODH) is a family 2 DHODH that interacts with cell membranes in order to promote catalysis. The membrane association is supposedly made via an extension found in the enzyme's N-terminal. In the present work, we used site directed spin labeling (SDSL) to specifically place a magnetic probe at positions 2, 5, 19, and 21 within the N-terminal and thus monitor, by using Electron Spin Resonance (ESR), dynamics and structural changes in this region in the presence of a membrane model system. Overall, our ESR spectra show that the N-terminal indeed binds to membranes and that it experiences a somewhat high flexibility that could be related to the role of this region as a molecular lid controlling the entrance of the enzyme's active site and thus allowing the enzyme to give access to quinones that are dispersed in the membrane and that are necessary for the catalysis.
Resumo: O conceito de proteína e sua síntese são importantes para a compreensão de processos em biotecnologia, por exemplo, a produção de novos fármacos, área em avanço nas últimas décadas. Assim, o objetivo desse trabalho foi verificar, dentre alunos do Ensino Médio, quais tipos de concepções eles têm ou trazem sobre proteína e síntese proteica, e que tipo de influência pode ter contribuído para a formulação de tais concepções, através de um questionário diagnóstico, composto por questões abertas, aplicado a 133 alunos de uma escola pública e de uma particular. Os resultados analisados basearam-se em categorização de respostas. Concluímos que, mesmo os alunos já tendo estudado assuntos relativos a proteínas, ainda carregavam traços de concepções alternativas, o que forneceu informações valiosas sobre possíveis falhas no processo de aprendizagem. Assim, para que haja uma "ressignificação" desses conceitos, é necessário que as discussões desse tema sejam ampliadas, vinculando-os aos conteúdos correlatos previamente trabalhados.Palavras-chave: Proteína. Ensino de biologia. Ensino Médio. Ensino-aprendizagem. Abstract:The concept of protein and its synthesis is important in order to understand biotechnology processes, such as the production of new drugs, an area in great progress. Thus, this study aimed to verify, among high school students, what kinds of ideas these students have about protein and protein synthesis, and what kind of influence contributed to the formulation of such concepts, through a diagnostic questionnaire with open questions, that was administered to 133 students from a public school and a private school. The results analyzed were based on the categorization of responses. We conclude that although the students having already studied the issues related to proteins, they still carried traces of alternative conceptions, which provided valuable information about possible failures in the learning process. Thus, to have a "reinterpretation" of these concepts, it is necessary that the discussions of this topic are expanded, linking them to related content which has previously been researched.
Ao pensarmos o Ensino de Física para alunos com deficiência visual, a linguagem matemática mostra-se desafiadora, pois sua sintaxe bidimensional restringe-a a uma “cultura de videntes”. Com o desenvolvimento dos ledores de tela, tornou-se possível o acesso ao computador por pessoas com deficiência visual. No entanto a linguagem matemática convencional oferece certas barreiras à acessibilidade. Nosso objetivo foi investigar as possibilidades e limitações ao se introduzir a linguagem LaTeX no contexto ativo de leitura e resolução de exercícios de Física por parte de alunos com deficiência visual, por meio de um computador associado a um ledor de tela. À luz do referencial de Vigotski, em que a linguagem tem um papel central tanto do ponto de vista do processo de mediação simbólica quanto no mecanismo de compensação sócio-psicológica de pessoas com deficiência visual, o trabalho foi estruturado sob as bases da pesquisa qualitativa, sendo a interpretação dos dados baseada na Análise do Discurso em Bakhtin. Ao introduzirmos a Linguagem LaTeX no contexto da leitura e resolução de exercícios de Física por um aluno do ensino médio de uma escola pública, a associação entre LaTeX e ledor de tela não somente mostrou-se acessível como compreensível, revelando um potencial na diminuição das barreiras da acessibilidade à textos de Física por meio do computador.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.