| 1. |
|
|
| 2. |
- Enroth, Cristofer, et al.
(författare)
-
Crystal structure of a protein, structurally related to glycosyltransferases, encoded in the Rhodobacter blasticus atp operon
- 2008
-
Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - Amsterdam : Elsevier/North Holland. - 1570-9639 .- 1878-1454. ; 1784:2, s. 379-384
-
Tidskriftsartikel (refereegranskat)abstract
- The F1-ATP synthase atp operon in the proteobacterium Rhodobacter blasticus contains six open reading frames, encoding six hypothetical proteins. Five of these subunits, in the stoichiometry (ab)3gde make up the catalytic F1-ATP synthase complex similarly in bacteria, chloroplasts and mitochondria. The sixth gene of the Rb. blasticus atp operon, urf6, shows very little sequence homology to any protein of known structure or function. The gene has previously been cloned, the product (called majastridin) has been heterologously expressed in Escherichia coli, and purified to high homogeneity (Brosché et al. (1998) Eur. J. Biochem. 255: 87-92). We have solved the X-ray crystal structure and refined a model of majastridin to atomic resolution. Here we present the crystal structures of apo-majastridin and the complex of majastridin with Mn2+ and UDP and show it has extensive structural similarity to glycosyltransferases (EC 2.4). This is the first structure determined from a new group of distantly related bacterial proteins of at least six members. They share the identical amino acids that bind Mn2+and a triplet of amino acids in the putative sugar-binding site.
|
|
| 3. |
|
|
| 4. |
- Fängström, Britta, et al.
(författare)
-
A retrospective study of PBDEs and PCBs in human milk from the Faroe Islands
- 2005
-
Ingår i: Environmental Health. - 1476-069X. ; 4:12
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundPersistent organic pollutants (POPs) in wildlife and humans remain a cause of global concern, both in regard to traditional POPs, such as the polychlorinated biphenyls (PCBs), and emerging POPs, such as the polybrominated diphenyl ethers (PBDEs). To determine the time related concentrations, we analyzed human milk for these substances at three time points between 1987 and 1999. Polychlorobiphenylols (OH-PCBs), the dominating class of PCB metabolites, some of which are known to be strongly retained in human blood, were also included in the assessment.MethodsWe obtained milk from the Faroe Islands, where the population is exposed to POPs from their traditional diet (which may include pilot whale blubber). In addition to three pools, nine individual samples from the last time point were also analyzed. After cleanup, partitioning of neutral and acidic compounds, and separation of chemical classes, the analyses were carried out by gas chromatography and/or gas chromatography/mass spectrometry.ResultsCompared to other European populations, the human milk had high PCB concentrations, with pool concentrations of 2300 ng/g fat 1987, 1600 ng/g fat in 1994, and 1800 ng/g fat in 1999 (based on the sum of eleven major PCB congeners). The nine individual samples showed great variation in PCB concentrations. The OH-PCBs were present in trace amounts only, at levels of approximately 1% of the PCB concentrations. The PBDE concentrations showed a clear increase over time, and their concentrations in human milk from 1999 are among the highest reported so far from Europe, with results of individual samples ranging from 4.7 to 13 ng/g fat.ConclusionAlthough remote from pollution sources, the Faroe Islands show high concentrations of POPs in human milk, particularly PCBs, but also PBDEs. The PBDEs show increasing concentrations over time. The OH-PCB metabolites are poorly transferred to human milk, which likely is related to their acidic character.
|
|
| 5. |
- Fängström, Britta, et al.
(författare)
-
Analys av polybromerade difenyletrar (PBDE) och hexabromcyklododekan (HBCDD) i human mjölk från Stockholm : en tidstrends studie
- 2005
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the present study was to assess the temporal trends of polybrominated diphenyl ethers (PBDEs), including decaBDE, and hexabromocyclododecane (HBCDD) in mothers milk from the Stockholm area. The pooled samples were covering the time period 1980 to 2004, with emphasis on samples from the last ten years. The temporal trend of PBDEs must be expressed on a congener basis since the development of the individual PBDE congener concentrations differ. BDE-47, -99 and -100 concentrations reached a peak in the mid 1990’s and are now clearly showing decreasing levels. BDE-153 concentrations increased until year 2000 and thereafter the concentrations may level off but it is yet not clear how the concentrations of this PBDE congener will develop over the next few years. It is not possible to quantify decaBDE (BDE-209) in the human milk. This may be due to poor transfer to the milk lipids but most likely it is a result of the short half-life of this compound in human blood. HBCDD concentrations are 2004, approximately four times the concentration in 1980 showing an increasing temporal trend until the early 2000’s. It is too early to judge if the levels are decreasing or leveling off. The HBCDD concentrations are in a range between BDE-47 and BDE-99 and BDE-100.
|
|
| 6. |
- Fängström, Britta, et al.
(författare)
-
Rapport till Naturvårdsverket för projektet "Analys av polybromerade difenyletrar (PBDE) och hexabromcyklododekan (HBCDD) i human mjölk från Stockholm – en tidstrends studie [Dnr 721-2653-05Mm]
- 2005
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the present study was to assess the temporal trends of polybrominated diphenyl ethers (PBDEs), including decaBDE, and hexabromocyclododecane (HBCDD) in mothers milk from the Stockholm area. The pooled samples were covering the time period 1980 to 2004, with emphasis on samples from the last ten years. The temporal trend of PBDEs must be expressed on a congener basis since the development of the individual PBDE congener concentrations differ. BDE-47, -99 and -100 concentrations reached a peak in the mid 1990’s and are now clearly showing decreasing levels. BDE-153 concentrations increased until year 2000 and thereafter the concentrations may level off but it is yet not clear how the concentrations of this PBDE congener will develop over the next few years. It is not possible to quantify decaBDE (BDE-209) in the human milk. This may be due to poor transfer to the milk lipids but most likely it is a result of the short half-life of this compound in human blood. HBCDD concentrations are 2004, approximately four times the concentration in 1980 showing an increasing temporal trend until the early 2000’s. It is too early to judge if the levels are decreasing or leveling off. The HBCDD concentrations are in a range between BDE-47 and BDE-99 and BDE-100.
|
|
| 7. |
- Kalbin, Georgi, et al.
(författare)
-
Effects of UV-B in biological and chemical systems : equipment for wavelength dependence determination
- 2005
-
Ingår i: Journal of Biochemical and Biophysical Methods. - : Elsevier BV. - 0165-022X .- 1872-857X. ; 65:1, s. 1-12
-
Tidskriftsartikel (refereegranskat)abstract
- The thinning of the stratospheric ozone layer has prompted a large number of studies of UV-B-induced effects in biological and chemical systems. The wavelength dependency of such effects is of interest from mechanistic, physiological or economic points of view. Here, we describe an apparatus for determining the wavelength dependency of UV-B effects in biological and chemical systems. The apparatus consists of a high intensity UV radiation source and narrow bandpass filters to produce UV radiation in even intervals (between 280 and 360 nm). The usefulness of the equipment is demonstrated in two different systems: 1) Chalcone synthase (CHS) gene is up-regulated by UV-B radiation. Therefore quantitative analysis of the CHS gene expression was chosen in the present investigation for studies of the wavelength dependency of gene expression regulation in plants. Maximum induction of CHS expression was found at 300 nm with a 12-fold induction compared with the control; 2) The wavelength dependency of formation of dioxin-like photoproducts from the brominated flame retardant decabrominated diphenyl ether (DeBDE) is described. This is an example of UV-B-induced conversion of non-toxic species into a number of products of which some may be toxic in the environment. In the UV interval studied, the highest dioxin-like activity was found in the sample irradiated at 330 nm and therefore this wavelength is most important for the mechanism involved in photoconversion of DeBDE.
|
|
| 8. |
|
|
| 9. |
- Kalbina, Irina, et al.
(författare)
-
Supplementary ultraviolet-B irradiation reveals differences in stress responses between Arabidopsis thaliana ecotypes
- 2006
-
Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 29:5, s. 754-763
-
Tidskriftsartikel (refereegranskat)abstract
- Irradiation of Arabidopsis thaliana ecotypes C24, Wassilewskija (Ws) and Columbia-0 (Col-0) with supplementary ultraviolet-A+B (UV-A+B) radiation revealed ecotype-specific differences in expression of the gene for the pathogenesis-related protein PR-5. C24 showed an increased expression level of PR-5 (5- and 20-fold higher compared with Col-0 and Ws, respectively). Expression of other molecular markers such as CHS (encoding chalcone synthase), MEB5.2 [encoding a gene strongly up-regulated by ultraviolet-B (UV-B)] and PYROA [encoding a pyridoxine (Vitamin B6) biosynthesis enzyme] only showed slight differences between ecotypes. Oxidative stress during UVA+B exposure was monitored by staining for H2O2. This analysis also revealed important ecotype-specific differences. 'H2O2 hot spots' were found in C24, whereas an even distribution of H2O2 was found in Ws and Col-0. Necrotic lesions also appeared on C24 leaves after prolonged UV-B exposure. There was a reverse correlation between the H2O2 steady-state concentration and the PR-5 gene expression; Ws showed the highest level of H2O2 accumulation but the lowest expression level of the PR-5 gene. Furthermore, application of paraquat on the rosettes led to similar PR-5 expression and H2O2 accumulation patterns as were found after UV-A+B irradiation. The observed ecotypic differences were also reflected in a statistically significant UV-B-dependent decrease in biomass, rosette size and leaf area for Ws, but not for C24 and Col-0. Our results show that a significant ecotype-specific genetic variability in general UV-B responses in Arabidopsis exists. Moreover, the signal transduction or gene regulation pathway for PR-5 differs from the other molecular markers used in this study.
|
|
| 10. |
- Kalbina, Irina, 1961-
(författare)
-
The molecular mechanisms behind perception and signal transduction of UV-B irradiation in Arabidopsis thaliana
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Elevation of UV-B radiation (280-315 nm), occurring as a result of depletion of the stratospheric ozone, causes a number of physiological and biochemical changes in plants. Damage to the photosynthetic apparatus (including the bleaching of the pigments which trap the sun's energy), to the processes of cell division and growth regulation, and to the composition and replication of genetic material are just some of these changes. The consequences include reduction in growth yield, changes in levels and effects of plant hormones and secondary metabolites, and alteration of interactions between plants and other organisms.This thesis deals with several mechanistic questions related to regulation of responses during UV-B stress in plants. Our results show significant ecotype-specific variability in UV-B response in the model plant Arabidopsis thaliana. Differences at the molecular level (expression of PR-5 and steady-state concentration of H2O2) resulted in statistically significant differences in biomass, rosette size and leaf area. Therefore, it is of great importance to pay attention to the responses of the background ecotypes when for instance studying mechanisms of responses toward ultraviolet-B radiation in mutants.Using a DNA microarray approach, we found a number of novel genes to be differentially expressed under UV-B radiation. Two of the genes (PYROA and MEB5.2) were later used as molecular markers for monitoring of UV-B stress. Promoters of PYROA and MEB5.2 were compared with promoters of genes for the phenylpropanoid pathway. The comparisons indicated only few common elements with the UV-B-regulated promoters of CHS, PAL and CHI. In contrast, the genes identified as being UV-B regulated in this study (MEB5.2, PYROA and UBQ3), completely lacked elements required for the UV-B induction of CHS, indicating that these genes are regulated by different transcription factors. In addition, novel unidentified cis-elements are probably also present upstream of the transcription start.Reverse and forward genetics were used for searching novel genes responsive to UV-B and for examination of proposed candidates of the UV-B signal transduction chain. Screening of more than 2000 T-DNA mutants for differential response to UV-B resulted in the identification of a mutant displaying insensitivity to UV-B induced inhibition of hypocotyl growth. By using the corresponding knock-out mutants, the involvement of NADPH oxidase and MAPK phosphatase 1 in UV-B signalling was demonstrated.For the plant to be able to respond appropriately to UV-B irradiation, UV-B quanta have to be absorbed. There are indirect evidences for the existence of specific UV-B receptor(s), whereas the receptor itself still remains unknown. By the classical approach of action spectroscopy, we undertook an attempt to identify the absorption spectra of the chromophore(s) sensing UV-B radiation in plants. The investigated molecular markers revealed the presence of two potential chromophores absorbing in the UV-B region and peaking at 280-290 and 300 nm, respectively.
|
|
