| 1. |
- Aurelius, Oskar, et al.
(författare)
-
The Crystal Structure of Thermotoga maritima Class III Ribonucleotide Reductase Lacks a Radical Cysteine Pre-Positioned in the Active Site
- 2015
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:7
-
Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to deoxyribonucleotides, the building blocks for DNA synthesis, and are found in all but a few organisms. RNRs use radical chemistry to catalyze the reduction reaction. Despite RNR having evolved several mechanisms for generation of different kinds of essential radicals across a large evolutionary time frame, this initial radical is normally always channelled to a strictly conserved cysteine residue directly adjacent to the substrate for initiation of substrate reduction, and this cysteine has been found in the structures of all RNRs solved to date. We present the crystal structure of an anaerobic RNR from the extreme thermophile Thermotoga maritima (tmNrdD), alone and in several complexes, including with the allosteric effector dATP and its cognate substrate CTP. In the crystal structure of the enzyme as purified, tmNrdD lacks a cysteine for radical transfer to the substrate pre-positioned in the active site. Nevertheless activity assays using anaerobic cell extracts from T. maritima demonstrate that the class III RNR is enzymatically active. Other genetic and microbiological evidence is summarized indicating that the enzyme is important for T. maritima. Mutation of either of two cysteine residues in a disordered loop far from the active site results in inactive enzyme. We discuss the possible mechanisms for radical initiation of substrate reduction given the collected evidence from the crystal structure, our activity assays and other published work. Taken together, the results suggest either that initiation of substrate reduction may involve unprecedented conformational changes in the enzyme to bring one of these cysteine residues to the expected position, or that alternative routes for initiation of the RNR reduction reaction may exist. Finally, we present a phylogenetic analysis showing that the structure of tmNrdD is representative of a new RNR subclass IIIh, present in all Thermotoga species plus a wider group of bacteria from the distantly related phyla Firmicutes, Bacteroidetes and Proteobacteria.
|
|
| 2. |
- Ekberg, Margareta Stigsdotter, 1955-
(författare)
-
Dom kallar oss värstingar : Om ungas lärande i mötet med skola, socialtjänst och polis
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is of primary concern, both from the perspective of the individual and of society at large, to take measures to prevent the occurrence of a negative development amongst young people. The starting point of this dissertation is the notion that interpersonal interactions that occur between people contribute to a process of learning, thus focus is placed upon the pedagogic interactions between society's authorities and young people in trouble. How such interactions contribute to the process of learning regarding the young people, and what that learning entails, is seen as a vital pedagogic question. The overriding aim of the dissertation is to identify aspects of learning that occur during the interactions between society's authorities and young people in trouble, in order to contribute to an understanding of how such interactions can be developed in a constructive manner.The thesis is based on the theories of man as a social being, dependent on relationships and interaction for the process of knowledge. The empirical study includes interviews with teachers, social workers, police officers and young people. Vignettes have formed the basis of discussions about the measures and initiatives taken by society and the types of experience the young people feel the measures and initiatives have led to. Since an element of authority is a component of the relationship between the representatives of society and the young people, the concept of governmentality formulated by Foucault has been used in the process of analysis. Also von Wright's concepts of punctual and relational perspective have been used in this process. The purpose of this study is to attempt to determine what consequences the various perspectives taken in the interactions may lead to, in relation to the knowledge these young people develop about themselves and about society.The result shows that society's representatives among themselves have different views of young people in trouble. Young people's experiences of interactions with society's representatives argue for the fact that their backgrounds often direct the course of the interaction and its contents. Young people testify about irrelevant measures and initiatives taken by society; that they are subject to prejudice and that the principle of "equality before the law" is not observed. Their experience has led them to feel that they have less of human dignity. The dissertation ends up in a discussion about the prerequisites necessary, in order that pedagogic interactions between a person in authority and young people in difficulties may proceed from a relational perspective. The ability to take the young person's perspective would thereby be a central aspect in the discussion about what measures and initiatives taken by society are appropriate to change a troubled lifestyle.
|
|
| 3. |
- Johansson, Renzo, et al.
(författare)
-
High-resolution crystal structures of the flavoprotein NrdI in oxidized and reduced states – an unusual flavodoxin
- 2010
-
Ingår i: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 277:20, s. 4265-4277
-
Tidskriftsartikel (refereegranskat)abstract
- The small flavoprotein NrdI is an essential component of the class Ib ribonucleotide reductase system in many bacteria. NrdI interacts with the class Ib radical generating protein NrdF. It is suggested to be involved in the rescue of inactivated diferric centres or generation of active dimanganese centres in NrdF. Although NrdI bears a superficial resemblance to flavodoxin, its redox properties have been demonstrated to be strikingly different. In particular, NrdI is capable of two-electron reduction, whereas flavodoxins are exclusively one-electron reductants. This has been suggested to depend on a lesser destabilization of the negatively-charged hydroquinone state than in flavodoxins. We have determined the crystal structures of NrdI from Bacillus anthracis, the causative agent of anthrax, in the oxidized and semiquinone forms, at resolutions of 0.96 and 1.4 Å, respectively. These structures, coupled with analysis of all curated NrdI sequences, suggest that NrdI defines a new structural family within the flavodoxin superfamily. The conformational behaviour of NrdI in response to FMN reduction is very similar to that of flavodoxins, involving a peptide flip in a loop near the N5 atom of the flavin ring. However, NrdI is much less negatively charged than flavodoxins, which is expected to affect its redox properties significantly. Indeed, sequence analysis shows a remarkable spread in the predicted isoelectric points of NrdIs, from approximately pH 4–10. The implications of these observations for class Ib ribonucleotide reductase function are discussed.
|
|
| 4. |
|
|
| 5. |
- Kristofferzon, Marja-Leena, 1950-, et al.
(författare)
-
Evaluation of a Swedish version of the Watts Sexual Function Questionnaire (WSFQ) in persons with heart disease: A pilot study
- 2010
-
Ingår i: European Journal of Cardiovascular Nursing. - Amsterdam : Elsevier. - 1474-5151 .- 1873-1953. ; 9:3, s. 168-174
-
Tidskriftsartikel (refereegranskat)abstract
- Background: As part of preparation for a Swedish multicentre study, exploring sexual and married life in patients with myocardial infarction and their partners, a Swedish validated instrument was required. Aims:The aim of this pilot study was to evaluate the validity and reliability of a Swedish version of the Watts Sexual Function Questionnaire (WSFQ) among persons with a heart disease.Methods:A convenience sample of 79 persons (47 men and 32 women) living with a heart disease was recruited from the members of the National Association of Heart and Lung Patients. They completed a Swedish version of the WSFQ on two occasions. Results:Two separate factor analyses each revealed a two-factor structure on both occasions: “Sexual appetite” and “Sexual expectations ”with gender-neutral questions and “Sexual sensitiveness” and “Sexual ability” with gender-specific questions. Cronbach's alpha coefficients ranged from 0.48 to 0.86 and test – retest values for all but one question exceeded 0.70.Conclusions:The Swedish version of the WSFQ showed good validity and stability and acceptable internal homogeneity. Extended evaluations of the questionnaire are recommended.
|
|
