Solution structure and pressure response of thioredoxin-1 of Plasmodium falciparum

We present here the solution structures of the protein thioredoxin-1 from Plasmodium falciparum (PfTrx-1), in its reduced and oxidized forms. They were determined by high-resolution NMR spectroscopy at 293 K on uniformly 13C-, 15N-enriched, matched samples allowing to identification of even small structural differences. PfTrx-1 shows an α/β-fold with a mixed five-stranded β-sheet that is sandwiched between 4 helices in a β1 α1 β2 α2 β3 α3 β4 β5 α4 topology. The redox process of the CGPC motif leads to significant structural changes accompanied by larger chemical shift changes from residue Phe25 to Ile36, Thr70 to Thr74, and Leu88 to Asn91. By high-field high-pressure NMR spectroscopy, rare conformational states can be identified that potentially are functionally important and can be used for targeted drug development. We performed these experiments in the pressure range from 0.1 MPa to 200 MPa. The mean combined, random-coil corrected B1* values of reduced and oxidized thioredoxin are quite similar with -0.145 and -0.114 ppm GPa-1, respectively. The mean combined, random-coil corrected B2* values in the reduced and oxidized form are 0.179 and 0.119 ppm GPa-2, respectively. The mean ratios of the pressure coefficients B2/B1 are -0.484 and -0.831 GPa-1 in the reduced and oxidized form respectively. They differ at some points in the structure after the formation of the disulfide bond between C30 and C33. The thermodynamical description of the pressure dependence of chemical shifts requires the assumption of at least three coexisting conformational states of PfTrx-1. These three conformational states were identified in the reduced as well as in the oxidized form of the protein, therefore, they represent sub-states of the two main oxidation states of PfTrx-1

Ceramic cells for high pressure NMR spectroscopy of proteins

Application of high pressure to biological macromolecules can be used to find new structural states with a smaller specific volume of the system. High pressure NMR spectroscopy is a most promising analytical tool for the study of these states at atomic resolution. High pressure quartz cells are difficult to handle, high quality sapphire high pressure cells are difficult to obtain commercially. In this work, we describe the use of high pressure ceramic cells produced from yttrium stabilized ZrO2 that are capable of resisting pressures up to 200 MPa. Since the new cells should also be usable in the easily damageable cryoprobes a completely new autoclave for these cells has been constructed, including an improved method for pressure transmission, an integrated safety jacket, a displacement body, and a fast self-closing emergency valve.DF

NMR assignments of oxidised thioredoxin from Plasmodium falciparum

During its life cycle, the malaria parasite Plasmodium falciparum is found intracellular to human erythrocytes, where its survival and ability to multiply critically depends on the control of the environment redox state. Thioredoxin is a small protein containing 104 amino acids that is part of the parasite specific redox system. During the catalytic cycle it alternates between a reduced and oxidised form. Here we report the complete resonance assignment of Plasmodium falciparum thioredoxin in its oxidized form by heteronuclear multidimensional spectroscopy. The obtained chemical shifts differ significantly from those reported earlier for this protein in its reduced stat

Pulsed pressure perturbations, an extra dimension in NMR spectroscopy of proteins

The introduction of multidimensional NMR spectroscopy was a breakthrough in biological NMR methodology because it allowed the unequivocal correlation of different spin states of the system. The introduction of large pressure perturbations in the corresponding radio frequency (RF) pulse sequences adds an extra structural dimension into these experiments. We have developed a microprocessor-controlled pressure jump unit that is able to introduce fast, strong pressure changes at any point in the pulse sequences. Repetitive pressure changes of 80 MPa in the sample tube are thus feasible in less than 30 ms. Two general forms of these experiments are proposed here, the pressure perturbation transient state spectroscopy (PPTSS) and the pressure perturbation state correlation spectroscopy (PPSCS). PPTSS can be used to measure the rate constants and the activation energies and activation volumes for the transition between different conformational states including the folded and unfolded state of proteins, for polymerization-depolymerization processes, and for ligand binding at atomic resolution. PPSCS spectroscopy correlates the NMR parameters of different pressure-induced states of the system, thus allowing the measurement of properties of a given pressure induced state such as a folding intermediate in a different state, for example, the folded state. Selected examples for PPTSS and PPSCS spectroscopy are presented in this Article.DFGBFSFC

A successful strategy for the recovering of active P21, an insoluble recombinant protein of Trypanosoma cruzi

Structural studies of proteins normally require large quantities of pure material that can only be obtained through heterologous expression systems and recombinant technique. in these procedures, large amounts of expressed protein are often found in the insoluble fraction, making protein purification from the soluble fraction inefficient, laborious, and costly. Usually, protein refolding is avoided due to a lack of experimental assays that can validate correct folding and that can compare the conformational population to that of the soluble fraction. Herein, we propose a validation method using simple and rapid 1D H-1 nuclear magnetic resonance (NMR) spectra that can efficiently compare protein samples, including individual information of the environment of each proton in the structure.Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)INBEQMeDIUniv Fed Uberlandia, Inst Ciencias Biomed, BR-38400 Uberlandia, MG, BrazilUniv São Paulo, Inst Fis Sao Carlos, Sao Carlos, SP, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, Vila Mariana, SP, BrazilUniv Fed Minas Gerais, Inst Ciencias Biol, Dept Biol Geral, Belo Horizonte, MG, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, Vila Mariana, SP, BrazilFAPESP: 2010/51867-6FAPESP: 2012/21153-7FAPEMIG: APQ-00621-11FAPEMIG: APQ-00305-12CAPES: 23038.005295/2011-40Web of Scienc

Molecular structure and EPR spectra of the monocrystalline compound CuBr2(fdmp)2.

Estão sendo apresentados, neste trabalho, estudos estruturais e magnéticos do composto de [CuBr2(fdmp)2] utilizando as técnicas de difração de Raio-X e espectroscopia de EPR. a complexo cristaliza no grupo espacial P21/n com a=8.1653(47)&#197, b=10.432(3)&#197, c=13.385(4)&#197, &#946=100.12(4)&#176 e Z=2. Os íons de Cu(II), que estão em coordenação quadrado-planar trans ligando-se a dois Nitrogênios e dois Bromos, se encontram em centros de inversão. Somente urna linha de EPR e observada, proveniente do colapso das ressonâncias relativas aos dois íons de Cu(II) magneticamente não equivalentes, causado pela interação de troca. Devido a diferença significativa entre os pesos atômicos do Nitrogênio e Bromo, não e esperada urna simetria axial para o tensor g como é comum ocorrer em vários complexos de Cu(II); de fato, a decomposição de g cristalino para os dois g moleculares revela três autovalores distintos. Alem disso, a direção de maior g não coincide exatamente com a normal ao quadrado-planar, como é comum nesses complexos: se encontra rodada de &#8764 5&#176 em direção ao Bromo, caracterizando um estado fundamental do tipo dx2-y2 com mistura de dyz. Outro fato incomum verificado foi a dependência do fator g com a freqüência e a presença de contribuições não-seculares, característicos de sistemas em que a freqüência de troca é próxima a freqüência de Larmor. Uma analise da variação angular da largura de linha de ressonância foi utilizada para a determinação do parâmetro de troca &#8204J&#8204. Está também incluído, neste trabalho, um método numérico de decomposição de g cristalino em g moleculares e sua comparação com métodos da literatura.In the present work, we discuss the structural and magnetic properties of the [CuBr2(fdmp)2] compound deduced from studies of X-ray diffraction and EPR spectroscopy. This complex crystallizes in the spatial group P21/n with a=8.1653(47)&#197, b=10.432(3)&#197, c=13.385(4)&#197, &#946=100.12(4)&#176 and Z=2. The copper ions, Cu (II), are in a square-planar coordination bound to two nitrogen and two bromine atoms. They are localized in inversion centers. Only one EPR line has been observed due to the collapse of the resonances of the two magnetically inequivalent Cu (II) ions caused by a strong exchange interaction between them. Since nitrogen and bromine have significantly different atomic weights we may not expect an axially symmetric g-tensor as is commonly found in many Cu (II) complexes. In fact, the decomposition of the experimental crystalline g-tensor into two molecular tensors reveals three distinct eigen-values. Furthermore, the axis of the largest molecular eigen-value does not exactly coincide with the normal of the square plane: it is rotated by &#8764 5&#176 toward the bromine atom which characterizes a dx2-y2 ground state with some contribution from a dyz state. Another unusual fact that has been revealed in our studies is the frequency dependence of the g-factor, due to the presence of non-secular contributions to Hamiltonian, which are characteristic for systems with a exchange frequency near the Larmor frequency. In order to determine the exchange factor &#8204J&#8204, we analyzed the angular dependence of the line broadening. In the present work we also included a numerical method for the decomposition of the crystalline g-tensor into molecular ones and compared it with other methods found in the literature

Structure determination of proteins by NMR: application to a His15Ala mutant of HPr from staphylococcus aureus.

A técnica de espectroscopia por Ressonância Magnética Nuclear (NMR) de alta resolução foi utilizada para estudos estruturais em duas biomoléculas: a proteína HPr da bactéria Staphylococcus aureus, e o peptídeo C da insulina humana. Ambas estão relacionadas com a regulação da absorção de glicose pelas células, no primeiro caso em procariontes, e no segundo em organismos superiores. A proteína HPr (\"Histidine-containing protein\") de Staphylococcus aureus é uma das componentes centrais do sistema PTS (fosfoenolpiruvato:açúcar-fosfotransferase) de translocação grupal, responsável pelo transporte ativo de açúcar para o interior da célula bacterial. Nesse processo, a His15 do sítio ativo de HPr é fosforilada pela enzima EI, transferindo, a seguir, o grupo fosfato para a enzima EUA A mutação His15&#8594Ala interrompe a transferência do grupo fosfato; apesar disso, a afinidade entre HPr(H15A) e as enzimas EI/EIlA se mostrou semelhante à da nativa. Utilizando técnicas de NMR bidimensionais (COSY, TOCSY, NOESY, HSQC) etridimensionais (HNCA, HNCO, NOESY-HSQC) foi determinada a estrutura da mutante His15&#8594Ala de HPr de S. aureus. Sua estrutura consiste de um sanduíche-aberto, composto de 3 hélices-a paralelamente empacotadas contra uma folha formada por 4 fitas-&#946 anti-paralelas. Esse padrão é encontrado em todas as proteínas HPr já determinadas em diversas espécies, divergindo, porém, significativamente da estrutura previamente publicada para a proteína nativa de S. aureus com relação à orientação relativa de alguns elementos de estrutura secundária. Através de uma análise detalhada dos espectros NOESY das proteínas HPr mutante e nativa puderam ser encontradas diferenças conformacionais na região em tomo do sítio-ativo. Uma comparação com as outras estruturas de HPr já publicadas revelou uma maior semelhança entre a proteína mutante de S. aureus e a proteína no complexo HPr/EI de E. coli, fornecendo evidências de que a estrutura encontrada para a mutante represente a conformação assumida pela proteína HPr no momento de sua interação com a enzima EI, assim explicando a sua afinidade inalterada. O peptídeo-C da proinsulina é importante para a biosíntese da insulina, tendo sido considerado, por muito tempo, biologicamente inerte. Estudos recentes em pacientes diabéticos retomaram a discussão quanto a sua possível atividade reguladora. Utilizando a técnica de espectroscopia de NMR bidimensional (COSY, TOCSY, NOESY), foram realizados estudos estruturais no peptídeo-C da proinsulina humana. Quando dissolvido em 50%/50% água e TFE, o peptídeo-C apresentou 3 regiões centrais (9-12, 15-18, 22-25) com tendência à formação de dobras, uma região N-terminal (2-5) com 2 conformações em voltas-&#946 tipo I e I, e uma região Cterminal (26-31), de conformação extremamente bem definida, incluindo uma volta-&#946 tipo III\' (27-30). Em estudos descritos na literatura já foi demonstrada a atividade do pentapeptídeo C-terminal (EGSLQ), na forma de interações quirais com um receptor ainda desconhecido. Estudos anteriores por NMR prevêem a existência de uma estrutura na região C-terminal, a qual foi denominada de \"CA-Knuckle\". Nossa proposta é que a estrutura aqui obtida para o pentapeptídeo C-terminal seja justamente o \"CA-Knuckle\", representando o sítio-ativo do peptídeo-C da proinsulina humana.High resolution Nuclear Magnetic Resonance spectroscopy has been used for structural studies on two biological macromolecules; the HPr protein from the bacterium Staphylococcus aureus, and the Cpeptide from human proinsulin. Both are related to the regulation of glucose absorption by celIs, the former case in prokaryotes and the latter in higher organisms. The HPr protein (Histidine Containing Protein) from S. aureus is one of the central components of the PTS (Phosphoenolpyruvate;sugar-phosphotransferase) system responsible for the active transport of sugars into the bacterial celI. During this process, His15 of the HPr active site is phosphorylated by enzyme I (EI), and then subsequently transfers this phosphate onto enzyme lIA (EIIA). The His15&#8594Ala mutant of HPr, whilst unable to participate in phosphate transfer, nevertheless retains similar affinities for both EI and EIIA. Using two-dimensional (COSY, TOCSY, NOESY, HSQC) and three-dimensional (HNCA, HNCO, NOESY-HSQC) NMR techniques, the structure of the His15Ala mutant of the HPr protein from S. aureus was determined. Its structure consists of an open &#946-sandwich, composed of three &#945-helices packed against a four-stranded anti-parallel &#946-sheet. This pattern has been seen in all other HPr proteins from other species so far determined but is markedly different from the previously published native structure from S. aureus with respect to the relative orientations of some of the elements of secondary structure. A detailed comparison of the native and mutant structures revealed differences in the conformation of the active site loop. The latter assumes a conformation similar to that seen in the structure of the complex between E. coli HPr and EI. This may explain the normal affinities of the mutant protein for EI and EIIA despite the absence of the active site histidine. The C-peptide of proinsulin is important for the biosynthesis of insulin but has been considered for a long time to be biologically inert. Recent studies in diabetic patients have stimulated a new debate concerning its possible regulatory role. Structural studies of the C-peptide were performed using two dimensional NMR spectroscopy (COSY, TOCSY and NOESY). ln the presence of 50% TFE three central regions of the molecule (residues 9-12, 15-18 and 22-25) showed tendencies to form ~-bends. The N terminal region (residues 2 to 5) was present in the form of either a type I or I\' &#946-turn, whilst the C terminal region (26-31) presented the most welI-defrnedstructure of the whole molecule which included a type III\' &#946-turn. The C-terminal pentapeptide (EGSLQ) has been described in the literature as being responsible for chiral interactions with an as yet uncharacterized receptor. Previous NMR studies have predicted the existence of a well-defined structure at the C-terminus of the C-peptide, kwown as the CAknuckle. We propose that the structure described here for the C-terminal pentapeptide is the CA-knuckle and represents the active site of the C-peptide of human proinsulin

Structure determination of proteins by NMR: application to a His15Ala mutant of HPr from staphylococcus aureus.

A técnica de espectroscopia por Ressonância Magnética Nuclear (NMR) de alta resolução foi utilizada para estudos estruturais em duas biomoléculas: a proteína HPr da bactéria Staphylococcus aureus, e o peptídeo C da insulina humana. Ambas estão relacionadas com a regulação da absorção de glicose pelas células, no primeiro caso em procariontes, e no segundo em organismos superiores. A proteína HPr (\"Histidine-containing protein\") de Staphylococcus aureus é uma das componentes centrais do sistema PTS (fosfoenolpiruvato:açúcar-fosfotransferase) de translocação grupal, responsável pelo transporte ativo de açúcar para o interior da célula bacterial. Nesse processo, a His15 do sítio ativo de HPr é fosforilada pela enzima EI, transferindo, a seguir, o grupo fosfato para a enzima EUA A mutação His15&#8594Ala interrompe a transferência do grupo fosfato; apesar disso, a afinidade entre HPr(H15A) e as enzimas EI/EIlA se mostrou semelhante à da nativa. Utilizando técnicas de NMR bidimensionais (COSY, TOCSY, NOESY, HSQC) etridimensionais (HNCA, HNCO, NOESY-HSQC) foi determinada a estrutura da mutante His15&#8594Ala de HPr de S. aureus. Sua estrutura consiste de um sanduíche-aberto, composto de 3 hélices-a paralelamente empacotadas contra uma folha formada por 4 fitas-&#946 anti-paralelas. Esse padrão é encontrado em todas as proteínas HPr já determinadas em diversas espécies, divergindo, porém, significativamente da estrutura previamente publicada para a proteína nativa de S. aureus com relação à orientação relativa de alguns elementos de estrutura secundária. Através de uma análise detalhada dos espectros NOESY das proteínas HPr mutante e nativa puderam ser encontradas diferenças conformacionais na região em tomo do sítio-ativo. Uma comparação com as outras estruturas de HPr já publicadas revelou uma maior semelhança entre a proteína mutante de S. aureus e a proteína no complexo HPr/EI de E. coli, fornecendo evidências de que a estrutura encontrada para a mutante represente a conformação assumida pela proteína HPr no momento de sua interação com a enzima EI, assim explicando a sua afinidade inalterada. O peptídeo-C da proinsulina é importante para a biosíntese da insulina, tendo sido considerado, por muito tempo, biologicamente inerte. Estudos recentes em pacientes diabéticos retomaram a discussão quanto a sua possível atividade reguladora. Utilizando a técnica de espectroscopia de NMR bidimensional (COSY, TOCSY, NOESY), foram realizados estudos estruturais no peptídeo-C da proinsulina humana. Quando dissolvido em 50%/50% água e TFE, o peptídeo-C apresentou 3 regiões centrais (9-12, 15-18, 22-25) com tendência à formação de dobras, uma região N-terminal (2-5) com 2 conformações em voltas-&#946 tipo I e I, e uma região Cterminal (26-31), de conformação extremamente bem definida, incluindo uma volta-&#946 tipo III\' (27-30). Em estudos descritos na literatura já foi demonstrada a atividade do pentapeptídeo C-terminal (EGSLQ), na forma de interações quirais com um receptor ainda desconhecido. Estudos anteriores por NMR prevêem a existência de uma estrutura na região C-terminal, a qual foi denominada de \"CA-Knuckle\". Nossa proposta é que a estrutura aqui obtida para o pentapeptídeo C-terminal seja justamente o \"CA-Knuckle\", representando o sítio-ativo do peptídeo-C da proinsulina humana.High resolution Nuclear Magnetic Resonance spectroscopy has been used for structural studies on two biological macromolecules; the HPr protein from the bacterium Staphylococcus aureus, and the Cpeptide from human proinsulin. Both are related to the regulation of glucose absorption by celIs, the former case in prokaryotes and the latter in higher organisms. The HPr protein (Histidine Containing Protein) from S. aureus is one of the central components of the PTS (Phosphoenolpyruvate;sugar-phosphotransferase) system responsible for the active transport of sugars into the bacterial celI. During this process, His15 of the HPr active site is phosphorylated by enzyme I (EI), and then subsequently transfers this phosphate onto enzyme lIA (EIIA). The His15&#8594Ala mutant of HPr, whilst unable to participate in phosphate transfer, nevertheless retains similar affinities for both EI and EIIA. Using two-dimensional (COSY, TOCSY, NOESY, HSQC) and three-dimensional (HNCA, HNCO, NOESY-HSQC) NMR techniques, the structure of the His15Ala mutant of the HPr protein from S. aureus was determined. Its structure consists of an open &#946-sandwich, composed of three &#945-helices packed against a four-stranded anti-parallel &#946-sheet. This pattern has been seen in all other HPr proteins from other species so far determined but is markedly different from the previously published native structure from S. aureus with respect to the relative orientations of some of the elements of secondary structure. A detailed comparison of the native and mutant structures revealed differences in the conformation of the active site loop. The latter assumes a conformation similar to that seen in the structure of the complex between E. coli HPr and EI. This may explain the normal affinities of the mutant protein for EI and EIIA despite the absence of the active site histidine. The C-peptide of proinsulin is important for the biosynthesis of insulin but has been considered for a long time to be biologically inert. Recent studies in diabetic patients have stimulated a new debate concerning its possible regulatory role. Structural studies of the C-peptide were performed using two dimensional NMR spectroscopy (COSY, TOCSY and NOESY). ln the presence of 50% TFE three central regions of the molecule (residues 9-12, 15-18 and 22-25) showed tendencies to form ~-bends. The N terminal region (residues 2 to 5) was present in the form of either a type I or I\' &#946-turn, whilst the C terminal region (26-31) presented the most welI-defrnedstructure of the whole molecule which included a type III\' &#946-turn. The C-terminal pentapeptide (EGSLQ) has been described in the literature as being responsible for chiral interactions with an as yet uncharacterized receptor. Previous NMR studies have predicted the existence of a well-defined structure at the C-terminus of the C-peptide, kwown as the CAknuckle. We propose that the structure described here for the C-terminal pentapeptide is the CA-knuckle and represents the active site of the C-peptide of human proinsulin

Molecular structure and EPR spectra of the monocrystalline compound CuBr2(fdmp)2.

Estão sendo apresentados, neste trabalho, estudos estruturais e magnéticos do composto de [CuBr2(fdmp)2] utilizando as técnicas de difração de Raio-X e espectroscopia de EPR. a complexo cristaliza no grupo espacial P21/n com a=8.1653(47)&#197, b=10.432(3)&#197, c=13.385(4)&#197, &#946=100.12(4)&#176 e Z=2. Os íons de Cu(II), que estão em coordenação quadrado-planar trans ligando-se a dois Nitrogênios e dois Bromos, se encontram em centros de inversão. Somente urna linha de EPR e observada, proveniente do colapso das ressonâncias relativas aos dois íons de Cu(II) magneticamente não equivalentes, causado pela interação de troca. Devido a diferença significativa entre os pesos atômicos do Nitrogênio e Bromo, não e esperada urna simetria axial para o tensor g como é comum ocorrer em vários complexos de Cu(II); de fato, a decomposição de g cristalino para os dois g moleculares revela três autovalores distintos. Alem disso, a direção de maior g não coincide exatamente com a normal ao quadrado-planar, como é comum nesses complexos: se encontra rodada de &#8764 5&#176 em direção ao Bromo, caracterizando um estado fundamental do tipo dx2-y2 com mistura de dyz. Outro fato incomum verificado foi a dependência do fator g com a freqüência e a presença de contribuições não-seculares, característicos de sistemas em que a freqüência de troca é próxima a freqüência de Larmor. Uma analise da variação angular da largura de linha de ressonância foi utilizada para a determinação do parâmetro de troca &#8204J&#8204. Está também incluído, neste trabalho, um método numérico de decomposição de g cristalino em g moleculares e sua comparação com métodos da literatura.In the present work, we discuss the structural and magnetic properties of the [CuBr2(fdmp)2] compound deduced from studies of X-ray diffraction and EPR spectroscopy. This complex crystallizes in the spatial group P21/n with a=8.1653(47)&#197, b=10.432(3)&#197, c=13.385(4)&#197, &#946=100.12(4)&#176 and Z=2. The copper ions, Cu (II), are in a square-planar coordination bound to two nitrogen and two bromine atoms. They are localized in inversion centers. Only one EPR line has been observed due to the collapse of the resonances of the two magnetically inequivalent Cu (II) ions caused by a strong exchange interaction between them. Since nitrogen and bromine have significantly different atomic weights we may not expect an axially symmetric g-tensor as is commonly found in many Cu (II) complexes. In fact, the decomposition of the experimental crystalline g-tensor into two molecular tensors reveals three distinct eigen-values. Furthermore, the axis of the largest molecular eigen-value does not exactly coincide with the normal of the square plane: it is rotated by &#8764 5&#176 toward the bromine atom which characterizes a dx2-y2 ground state with some contribution from a dyz state. Another unusual fact that has been revealed in our studies is the frequency dependence of the g-factor, due to the presence of non-secular contributions to Hamiltonian, which are characteristic for systems with a exchange frequency near the Larmor frequency. In order to determine the exchange factor &#8204J&#8204, we analyzed the angular dependence of the line broadening. In the present work we also included a numerical method for the decomposition of the crystalline g-tensor into molecular ones and compared it with other methods found in the literature