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Structural insight into Parkinson's disease treatment from drug-inhibited dopa decarboxylase
No full textFunctional and structural analysis of cis-proline mutants of Escherichia coli aspartate aminotransferase.
No full textTo elucidate the role of the two conserved cis-proline residues of aspartate aminotransferase (AspAT), one double and two single mutants of the enzyme from Escherichia coli (EcAspAT) were prepared: P138A, P195A and P138A/P195A in which the two prolines were replaced by alanine. The crystal structures of P195A and P138A/P195A have been determined at 2.3-2.1 A resolution. The wild-type geometry, including the cis conformation of the 194-195 peptide bond is retained upon substitution of proline 195 by alanine, whereas the trans conformation is adopted at the 137-138 peptide bond. Quite surprisingly, the replacement of each of the two prolines by alanine does not significantly affect either the activity or the stability of the protein. All the three mutants follow the same pathway as the wild type for unfolding equilibrium induced by guanidine hydrochloride [Herold, M., and Kirschner, K. (1990) Biochemistry 29, 1907-1913]. The kinetics of renaturation of P195A, where the alanine retains the wild-type cis conformation, is faster than wild type, whereas renaturation of P138A, which adopts the trans conformation, is slower. We conclude that cis-prolines seem to have been retained throughout the evolution of aspartate aminotransferase to possibly play a subtle role in directing the traffic of intermediates toward the unique structure of the native state, rather than to respond to the needs for a specific catalytic or functional role
Functional and structural analysis of cis-proline mutants of Escherichia coli aspartate aminotransferase.
No full textTo elucidate the role of the two conserved cis-proline residues of aspartate aminotransferase (AspAT), one double and two single mutants of the enzyme from Escherichia coli (EcAspAT) were prepared: P138A, P195A and P138A/P195A in which the two prolines were replaced by alanine. The crystal structures of P195A and P138A/P195A have been determined at 2.3-2.1 A resolution. The wild-type geometry, including the cis conformation of the 194-195 peptide bond is retained upon substitution of proline 195 by alanine, whereas the trans conformation is adopted at the 137-138 peptide bond. Quite surprisingly, the replacement of each of the two prolines by alanine does not significantly affect either the activity or the stability of the protein. All the three mutants follow the same pathway as the wild type for unfolding equilibrium induced by guanidine hydrochloride [Herold, M., and Kirschner, K. (1990) Biochemistry 29, 1907-1913]. The kinetics of renaturation of P195A, where the alanine retains the wild-type cis conformation, is faster than wild type, whereas renaturation of P138A, which adopts the trans conformation, is slower. We conclude that cis-prolines seem to have been retained throughout the evolution of aspartate aminotransferase to possibly play a subtle role in directing the traffic of intermediates toward the unique structure of the native state, rather than to respond to the needs for a specific catalytic or functional role
CRYSTALLIZATION AND PRELIMINARY X-RAY ANALYSIS OF THE BETA-ISOFORM OF GLUTAMATE DECARBOXYLASE FROM ESCHERICHIA COLI.
No full textGlutamate decarboxylase (GAD) is a vitamin B6 enzyme which catalyzes the α-decarboxylation of l-glutamate to γ-aminobutyric acid (GABA). Escherichia coli cells coexpress two highly homologous enzyme isoforms, GADα and GADβ. Well diffracting crystals of GADβ were obtained by taking advantage of the possibility of expressing each isoform separately. They belong to space group P31 or P32 with the unit-cell dimensions a = b = 115.6 and c = 206.6 Å and contain one GAD hexamer in the asymmetric unit. High-resolution synchrotron data were collected at 100 K for the native protein and a potential heavy-atom derivative
Functional and structural analysis of cis-proline mutants of Escherichia coli aspartate aminotransferase.
No full textFunctional and structural analysis of cis-proline mutants of Escherichia coli aspartate aminotransferase.
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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