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- Almstedt, Karin, 1980-, et al.
(författare)
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Unfolding a folding disease: folding, misfolding and aggregation of the marble brain syndrome-associated mutant H107Y of human carbonic anhydrase II
- 2004
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Ingår i: Journal of Molecular Biology. - Oxford : Elsevier. - 0022-2836 .- 1089-8638. ; 342:2, s. 619-633
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Tidskriftsartikel (refereegranskat)abstract
- Most loss-of-function diseases are caused by aberrant folding of important proteins. These proteins often misfold due to mutations. The disease marble brain syndrome (MBS), known also as carbonic anhydrase II deficiency syndrome (CADS), can manifest in carriers of point mutations in the human carbonic anhydrase II (HCA II) gene. One mutation associated with MBS entails the His107Tyr substitution. Here, we demonstrate that this mutation is a remarkably destabilizing folding mutation. The loss-of-function is clearly a folding defect, since the mutant shows 64% of CO2 hydration activity compared to that of the wild-type at low temperature where the mutant is folded. On the contrary, its stability towards thermal and guanidine hydrochloride (GuHCl) denaturation is highly compromised. Using activity assays, CD, fluorescence, NMR, cross-linking, aggregation measurements and molecular modeling, we have mapped the properties of this remarkable mutant. Loss of enzymatic activity had a midpoint temperature of denaturation (Tm) of 16 °C for the mutant compared to 55 °C for the wild-type protein. GuHCl-denaturation (at 4 °C) showed that the native state of the mutant was destabilized by 9.2 kcal/mol. The mutant unfolds through at least two equilibrium intermediates; one novel intermediate that we have termed the molten globule light state and, after further denaturation, the classical molten globule state is populated. Under physiological conditions (neutral pH; 37 °C), the His107Tyr mutant will populate the molten globule light state, likely due to novel interactions between Tyr107 and the surroundings of the critical residue Ser29 that destabilize the native conformation. This intermediate binds the hydrophobic dye 8-anilino-1-naphthalene sulfonic acid (ANS) but not as strong as the molten globule state, and near-UV CD reveals the presence of significant tertiary structure. Notably, this intermediate is not as prone to aggregation as the classical molten globule. As a proof of concept for an intervention strategy with small molecules, we showed that binding of the CA inhibitor acetazolamide increases the stability of the native state of the mutant by 2.9 kcal/mol in accordance with its strong affinity. Acetazolamide shifts the Tm to 34 °C that protects from misfolding and will enable a substantial fraction of the enzyme pool to survive physiological conditions.
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| 2. |
- Hedenas, Henrik, et al.
(författare)
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Changes Versus Homeostasis in Alpine and Sub-Alpine Vegetation Over Three Decades in the Sub-Arctic
- 2012
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Ingår i: Ambio. - : Springer Verlag (Germany). - 0044-7447 .- 1654-7209. ; 41, s. 187-196
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Tidskriftsartikel (refereegranskat)abstract
- Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977–1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites.
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| 5. |
- Ericsson, Per, et al.
(författare)
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Characterization of particulate emissions and methodology for oxidation of particulates from non-diesel combustion systems
- 2008
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Ingår i: SAE Technical Paper. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- Tailpipe particulate emissions, i.e., particle number, size distribution and total mass, from a series of four-cylinder engines with 2L displacement and power output of approximately 150 hp have been measured. The engines were in their respective vehicle installation, all midsize vehicles from various manufacturers, and represented different combustion concepts, i.e., port- and direct-injected vehicles and E5 and E85 fuels. The results are compared to post-Euro V emission standards for gasoline and biofuels using diesel as reference. The results show that the type of combustion and fuel significantly affect the particulate formation. In general, direct-injected engines show high particle numbers and mass compared to port-injected engines. The particulate number and total mass can be reduced by using biofuels, e.g., ethanol mixes, instead of gasoline. Moreover, an experimental procedure and setup facilitating precise studies of oxidation of particulates in realistic filter structures by well-controlled gas flow (composition and temperature) and sample (particulate load and temperature) conditions has been developed. The results from this method have been verified by using commercial soot as reference.
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| 6. |
- Fadeel, Bengt, et al.
(författare)
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Kostmann disease and other forms of severe congenital neutropenia
- 2021
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Ingår i: Acta Paediatrica. - : John Wiley & Sons. - 0803-5253 .- 1651-2227. ; 110:11, s. 2912-2920
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Tidskriftsartikel (refereegranskat)abstract
- Congenital neutropenia with autosomal recessive inheritance was first described by the Swedish paediatrician Rolf Kostmann who coined the term ‘infantile genetic agranulocytosis’. The condition is now commonly referred to as Kostmann disease. These patients display a maturation arrest of the myelopoiesis in the bone marrow and reduced neutrophil numbers and suffer from recurrent, often life-threatening infections. The molecular mechanism underlying congenital neutropenia has been intensively investigated, and mutations in genes that impinge on programmed cell death have been identified. The present review provides an overview of these studies.
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| 8. |
- Lindehammer, Sabina, et al.
(författare)
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Temporal trends of HLA genotype frequencies of type 1 diabetes patients in Sweden from 1986 to 2005 suggest altered risk
- 2008
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Ingår i: Acta Diabetologica. - : Springer Science and Business Media LLC. - 0940-5429 .- 1432-5233. ; 45:4, s. 231-5
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare the frequency of human leukocyte antigen (HLA) genotypes in 1-18-year-old patients with type 1 diabetes newly diagnosed in 1986-1987 (n = 430), 1996-2000 (n = 342) and in 2003-2005 (n = 171). We tested the hypothesis that the HLA DQ genotype distribution changes over time. Swedish type 1 diabetes patients and controls were typed for HLA using polymerase chain reaction amplification and allele specific probes for DQ A1* and B1* alleles. The most common type 1 diabetes HLA DQA1*-B1*genotype 0501-0201/0301-0302 was 36% (153/430) in 1986-1987 and 37% (127/342) in 1996-2000, but decreased to 19% (33/171) in 2003-2005 (P \ 0.0001). The 0501-0201/0501-0201 genotype increased from 1% in 1986-1987 to 7% in 1996-2000 (P = 0.0047) and to 5% in 2003-2005 (P > 0.05). This study in 1-18-year-old Swedish type 1 diabetes patients supports the notion that there is a temporal change in HLA risk.
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| 10. |
- Ruiz-Pavon, Lorena, et al.
(författare)
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Functionally important amino acids in the Arabidopsis thylakoid phosphate transporter: Homology modeling and site-directed mutagenesis
- 2010
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Ingår i: Biochemistry. - : American Chemical Society. - 0006-2960 .- 1520-4995. ; 49:30, s. 6430-6439
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Tidskriftsartikel (refereegranskat)abstract
- The anion transporter 1 (ANTR1) from Arabidopsis thaliana, homologous to the mammalian members of the solute carrier 17 (SLC17) family, is located in the chloroplast thylakoid membrane. When expressed heterologously in Escherichia coli, ANTR1 mediates a Na+-dependent active transport of inorganic phosphate (Pi). The aim of this study was to identify amino acid residues involved in Pi binding and translocation by ANTR1 and in the Na+ dependence of its activity. A three-dimensional structural model of ANTR1 was constructed using the crystal structure of glycerol 3-phosphate/phosphate antiporter from E. coli as a template. Based on this model and multiple sequence alignments, five highly conserved residues in plant ANTRs and mammalian SLC17 homologues have been selected for site-directed mutagenesis, namely, Arg-120, Ser-124, and Arg-201 inside the putative translocation pathway and Arg-228 and Asp-382 exposed at the cytoplasmic surface of the protein. The activities of the wild-type and mutant proteins have been analyzed using expression in E. coli and radioactive Pi transport assays and compared with bacterial cells carrying an empty plasmid. The results from Pi- and Na+-dependent kinetics indicate the following: (i) Arg-120 and Arg-201 may be important for binding and translocation of the substrate; (ii) Ser-124 may function as a transient binding site for Na+ ions in close proximity to the periplasmic side; (iii) Arg-228 and Asp-382 may participate in interactions associated with protein conformational changes required for full transport activity. Functional characterization of ANTR1 should provide useful insights into the function of other plant and mammalian SLC17 homologous transporters.
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