1,720,956 research outputs found
Two short protein domains are responsible for the nuclear localization of mouse spermine oxidase (mSMO) isoform
No full textCharacterization of a Lysine-Specific Histone Demethylase from Arabidopsis thaliana.
No full textArabidopsis thaliana has four genes with close homology to human histone H3 lysine 4 demethylase (HsLSD1), a component of various transcriptional corepressor complexes that often also contain histone deacetylases and the corepressor protein CoREST. All four Arabidopsis proteins contain a flavin amine oxidase domain and a SWIRM domain, the latter being present in a number of proteins involved in chromatin regulation. Here, we describe the heterologous expression and biochemical characterization of one of these Arabidopsis proteins (AtLSD1) and show that, similarly to HsLSD1, it has demethylase activity toward mono- and dimethylated Lys4 but not dimethylated Lys9 and Lys27 of histone 3. Modeling of the AtLSD1 three-dimensional structure using the HsLSD1 crystal structure as a template revealed a high degree of conservation of the residues building up the active site and some important differences. Among these differences, the most prominent is the lack of the HsLSD1 Tower domain, which has been shown to interact with CoREST and to be indispensable for HsLSD1 demethylase activity. This observation, together with AtLSD1 peculiar surface electrostatic potential distribution, suggests that the molecular partners of AtLSD1 are probably different from those of the human orthologue
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Functional diversity inside the Arabidopsis polyamine oxidase gene family
No full text""Polyamine oxidases (PAOs) are FAD-dependent enzymes involved in polyamine catabolism. All so far characterized PAOs from monocotyledonous plants, such as the apoplastic maize PAO, oxidize spermine (Spm) and spermidine (Spd) to produce 1,3-diaminopropane, H(2)O(2), and an aminoaldehyde, and are thus considered to be involved in a terminal catabolic pathway. Mammalian PAOs oxidize Spm or Spd (and\\\/or their acetyl derivatives) differently from monocotyledonous PAOs, producing Spd or putrescine, respectively, in addition to H(2)O(2) and an aminoaldehyde, and are therefore involved in a polyamine back-conversion pathway. In Arabidopsis thaliana, five PAOs (AtPAO1-AtPAO5) are present with cytosolic or peroxisomal localization and three of them (the peroxisomal AtPAO2, AtPAO3, and AtPAO4) form a distinct PAO subfamily. Here, a comparative study of the catalytic properties of recombinant AtPAO1, AtPAO2, AtPAO3, and AtPAO4 is presented, which shows that all four enzymes strongly resemble their mammalian counterparts, being able to oxidize the common polyamines Spd and\\\/or Spm through a polyamine back-conversion pathway. The existence of this pathway in Arabidopsis plants is also evidenced in vivo. These enzymes are also able to oxidize the naturally occurring uncommon polyamines norspermine and thermospermine, the latter being involved in important plant developmental processes. Furthermore, data herein reveal some important differences in substrate specificity among the various AtPAOs, which suggest functional diversity inside the AtPAO gene family. These results represent a new starting point for further understanding of the physiological role(s) of the polyamine catabolic pathways in plants.. . "
Characterization of a lysine-specific histone demethylase from Arabidopsis thaliana RID A-4573-2009
No full textArabidopsis thaliana has four genes with close homology to human histone H3 lysine 4 demethylase (HsLSD1), a component of various transcriptional corepressor complexes that often also contain histone deacetylases and the corepressor protein CoREST. All four Arabidopsis proteins contain a flavin amine oxidase domain and a SWIRM domain, the latter being present in a number of proteins involved in chromatin regulation. Here, we describe the heterologous expression and biochemical characterization of one of these Arabidopsis proteins (AtLSD1) and show that, similarly to HsLSD1, it has demethylase activity toward mono- and dimethylated Lys4 but not dimethylated Lys9 and Lys27 of histone 3. Modeling of the AtLSD1 three-dimensional structure using the HsLSD1 crystal structure as a template revealed a high degree of conservation of the residues building up the active site and some important differences. Among these differences, the most prominent is the lack of the HsLSD1 Tower domain, which has been shown to interact with CoREST and to be indispensable for HsLSD1 demethylase activity. This observation, together with AtLSD1 peculiar surface electrostatic potential distribution, suggests that the molecular partners of AtLSD1 are probably different from those of the human orthologue
Variations on the Author
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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