1,720,970 research outputs found
CRP is a global regulator of carbon catabolism and energy metabolism in Mycobacterium smegmatis
No full textMembers of the genus Mycobacterium respire using two terminal respiratory oxidases: a cytochrome bd-type menaquinol oxidase (encoded by cydABDC) or an aa3-type menaquinol-cytochrome c oxidase. During the transition to hypoxic (< 0.1% air saturation) conditions, cytochrome bd is induced in Mycobacterium smegmatis but the molecular mechanism governing this induction remains unknown. Analysis of the proposed cydABDC operon in M. smegmatis under hypoxic conditions revealed that cydAB and cydDC were not polycistronic. A transposon-mediated random mutagenesis was performed and revealed genes involved in redox homeostasis and defense against oxidase stress including KatG and PruC were required for cydAB operon expression. DNA-binding experiments were performed using a cydA promoter as target DNA and a DNA-binding histone-like protein (Hlp) was identified as protein bound to the cydAB promoter region. A cAMP receptor protein (CRP)-binding site (GTGAN6CCACA) was identified in the regulatory region of the cydAB operon and mutations in this sequence caused a significant reduction in cydA-lacZ expression.
The M. smegmatis mc2155 genome has two copies of CRP [Msmeg_0539 (Crp1) and Msmeg_6189 (Crp2)]. Phylogenetic analysis suggested that Crp1 is uniquely present in fast-growing mycobacteria, whilst Crp2 is closely related to CRP from other slow- growing mycobacteria. In addition, only Crp1 but not Crp2 could complement a Δcrp mutant of the Gram-negative bacterium, Pectobacterium atrosepticum. To dissect the physiological role of each Crp protein, transcriptional profiling studies using deletion mutants were conducted. Microarray analysis of the crp1 deletion mutant revealed 239 genes were differentially regulated including those involved in carbon catabolism and energy metabolism. However, a crp2-deletion mutant could not be obtained suggesting that this gene is essential for growth in M. smegmatis. Therefore, crp2 was conditionally expressed and transcriptional profiling studies were performed. Microarray analysis of the crp2 overexpression strain showed 58 genes were differentially regulated including genes from many biological processes. Identification of the CRP promoter consensus in M. smegmatis revealed that both Crp1 and Crp2 recognise the same consensus sequence yet the regulon of Crp1 is distinct from that of Crp2. Taken together, these data demonstrate that each Crp could be activated in response to unique signals. The mechanism of how each Crp is activated remains to be elucidated
CRP is a global regulator of carbon catabolism and energy metabolism in Mycobacterium smegmatis
No full textMembers of the genus Mycobacterium respire using two terminal respiratory oxidases: a cytochrome bd-type menaquinol oxidase (encoded by cydABDC) or an aa3-type menaquinol-cytochrome c oxidase. During the transition to hypoxic (< 0.1% air saturation) conditions, cytochrome bd is induced in Mycobacterium smegmatis but the molecular mechanism governing this induction remains unknown. Analysis of the proposed cydABDC operon in M. smegmatis under hypoxic conditions revealed that cydAB and cydDC were not polycistronic. A transposon-mediated random mutagenesis was performed and revealed genes involved in redox homeostasis and defense against oxidase stress including KatG and PruC were required for cydAB operon expression. DNA-binding experiments were performed using a cydA promoter as target DNA and a DNA-binding histone-like protein (Hlp) was identified as protein bound to the cydAB promoter region. A cAMP receptor protein (CRP)-binding site (GTGAN6CCACA) was identified in the regulatory region of the cydAB operon and mutations in this sequence caused a significant reduction in cydA-lacZ expression.
The M. smegmatis mc2155 genome has two copies of CRP [Msmeg_0539 (Crp1) and Msmeg_6189 (Crp2)]. Phylogenetic analysis suggested that Crp1 is uniquely present in fast-growing mycobacteria, whilst Crp2 is closely related to CRP from other slow- growing mycobacteria. In addition, only Crp1 but not Crp2 could complement a Δcrp mutant of the Gram-negative bacterium, Pectobacterium atrosepticum. To dissect the physiological role of each Crp protein, transcriptional profiling studies using deletion mutants were conducted. Microarray analysis of the crp1 deletion mutant revealed 239 genes were differentially regulated including those involved in carbon catabolism and energy metabolism. However, a crp2-deletion mutant could not be obtained suggesting that this gene is essential for growth in M. smegmatis. Therefore, crp2 was conditionally expressed and transcriptional profiling studies were performed. Microarray analysis of the crp2 overexpression strain showed 58 genes were differentially regulated including genes from many biological processes. Identification of the CRP promoter consensus in M. smegmatis revealed that both Crp1 and Crp2 recognise the same consensus sequence yet the regulon of Crp1 is distinct from that of Crp2. Taken together, these data demonstrate that each Crp could be activated in response to unique signals. The mechanism of how each Crp is activated remains to be elucidated
Implementation of Secure Data Transfer by using Symmetric (AES) and Asymmetric (RSA) with Digital Signature
Get PDFNowadays, Internet and network applications aregrowing very fast, so critical information is needed to protect .Crypto algorithms play a main role in information securitysystems. In this paper, we present secure data transfer by usinghybrid cryptosystem. It used cryptography for confidentially,authenticity and integrity of information during transmission.This system describes describes symmetric, asymmetric anddigital signature. This system implements a secure informationtransfer between any two parties so that they can securelytransmit and access critical information. To implement thissystem AES, RSA and digital signature with MD-5 algorithmsare used. The implementation is written in C# using MicrosoftVisual Studio 2005
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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