1,721,029 research outputs found
Short linear motifs characterizing snake venom and mammalian phospholipases a2
Full text linkSnake venom phospholipases A2 (PLA2s) have sequences and structures very similar to those of mammalian group I and II secretory PLA2s, but they possess many toxic properties, ranging from the inhibition of coagulation to the blockage of nerve transmission, and the induction of muscle necrosis. The biological properties of these proteins are not only due to their enzymatic activity, but also to protein–protein interactions which are still unidentified. Here, we compare sequence alignments of snake venom and mammalian PLA2s, grouped according to their structure and biological activity, looking for differences that can justify their different behavior. This bioinformatics analysis has evidenced three distinct regions, two central and one C-terminal, having amino acid compositions that distinguish the different categories of PLA2s. In these regions, we identified short linear motifs (SLiMs), peptide modules involved in protein–protein interactions, conserved in mammalian and not in snake venom PLA2s, or vice versa. The different content in the SLiMs of snake venom with respect to mammalian PLA2s may result in the formation of protein membrane complexes having a toxic activity, or in the formation of complexes whose activity cannot be blocked due to the lack of switches in the toxic PLA2s, as the motif recognized by the prolyl isomerase Pin1
Studio di una putativa proteasi nucleare essenziale per la cellula di lievito e conservata dagli archebatteri all'uomo
No full textIn questo lavoro analizziamo alcune caratteristiche della proteina Kae1 di Saccharomyces cerevisiae. Essa è codificata da un gene essenziale ed è classificata come metallo-proteasi in base all’omologia di sequenza con una O-Sialo-Glico-Endo-Peptidasi di Pasteurella haemolytica. Kae1, che è localizzata prevalentemente nel nucleo, fa parte di un complesso multi proteico al quale appartiene anche la proteina piD261/Bud32. Quest’ultima è una Ser-Thr protein chinasi appartenente ad una sub famiglia, molto conservata, originatasi prima della divergenza tra Archebatteri ed Eucarioti. Il suo ruolo nel lievito è essenziale per la normale crescita cellulare e anche l’omologo umano, PRPK, è probabilmente coinvolto nel controllo della crescita cellulare, dal momento che è in grado di fosforilare p53 in corrispondenza di Ser-15, evento che porta al blocco del ciclo cellulare in seguito a danni al DNA. Anche la sequenza di Kae1 è molto conservata ed il suo omolog umano è chiamato OSGEP.
Qui mostreremo come PRPK e OSGEP siano omologhi funzionali delle corrispondenti proteine di lievito, grazie a saggi di complementazione fenotipica e anche che le due proteine PRPK e OSGEP sono in grado di interagire tra loro a supporto di un rilevante significato fisiologico di tale interazione. Dimostreremo inoltre che il mantenimento del motivo di legame al metallo HCIGH in Kae1 e OSGEP è correlato all’attività di tali proteine, dato che la sostituzione delle due istidine causa un fenotipo letale indistinguibile dalla delezione genica. Il nostro interesse è rivolto anche alla caratterizzazione del legame del metallo, data la particolarità della presenza inusuale di una cisteina nel motivo.
L’aspettativa è quella di dimostrare l’attività catalitica in vitro della putativa proteasi Kae1 isolata da lievito e di confermare il legame dello ione metallico, definendo i residui coinvolti in tale legame, attraverso saggi di assorbimento atomico sulle proteine, di tipo selvatico e mutanti, espresse in E. coli
Oxime and thiazolidine chemoselective ligation reactions: a green method for cotton functionalization
Full text linkDuring the last years, the need to create textile materials provided with peculiar properties has grown significantly. In particular, new textiles are studied to be a first protection in the prevention of living organisms from pathogens. In this regard, modifying a textile material with biologically active compounds, such as antibacterial or antiviral peptides would be useful for many applications. Our work shows a study on the possibility of modifying cotton fabrics with peptides using thiazolidine and oxime chemoselective ligations. For this purpose, an enzymatic oxidation of cellulose in a heterogeneous phase and the possibility to reuse the oxidation solution for multiple times was successfully applied. Model peptides have been designed and synthesized in order to set up the conditions for conjugating peptides to cotton via either thiazolidine or oxime bond. A systematic study of the time, pH, and quantities needed for the best reaction conditions has been conducted. The efficiency and stability of the two chemoselective ligation bonds have been studied and compared
Isolated α-turns in peptides: a selected literature survey
No full textThe results of classifying into various types the 68 examples of isolated α-turns in the X-ray diffraction crystal structures of peptides documented in the literature are presented and discussed in this review article. α-Turns characterized by the trans disposition of all ω torsion angles are common for the backbone linear peptides investigated. In contrast, the cis arrangement of the N-terminal (ωi + 1) torsion angle, among those generated by the three residues internal to the α-turn, is a peculiar feature of 65% of the cyclic peptides. Among linear and cyclic peptides featuring the all-trans disposition of the ω torsion angles, only one third of the α-turns display φ,ψ values not too far from those characterizing regular α-helices. In general, our findings, taken together, suggest that a significant conformational diversity is compatible with the formation of an intramolecularly H-bonded C13-member pseudocycle (α-turn) in linear and cyclic peptides
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
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
- …
