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- Assarsson, Maria, et al.
(författare)
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Restoring proper radical generation by azide binding to the iron site of the E238A mutant R2 protein of ribonucleotide reductase from Escherichia coli.
- 2001
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 276:29, s. 26852-26859
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme activity of Escherichia coli ribonucleotide reductase requires the presence of a stable tyrosyl free radical and diiron center in its smaller R2 component. The iron/radical site is formed in a reconstitution reaction between ferrous iron and molecular oxygen in the protein. The reaction is known to proceed via a paramagnetic intermediate X, formally a Fe(III)-Fe(IV) state. We have used 9.6 GHz and 285 GHz EPR to investigate intermediates in the reconstitution reaction in the iron ligand mutant R2 E238A with or without azide, formate, or acetate present. Paramagnetic intermediates, i.e. a long-living X-like intermediate and a transient tyrosyl radical, were observed only with azide and under none of the other conditions. A crystal structure of the mutant protein R2 E238A/Y122F with a diferrous iron site complexed with azide was determined. Azide was found to be a bridging ligand and the absent Glu-238 ligand was compensated for by azide and an extra coordination from Glu-204. A general scheme for the reconstitution reaction is presented based on EPR and structure results. This indicates that tyrosyl radical generation requires a specific ligand coordination with 4-coordinate Fe1 and 6-coordinate Fe2 after oxygen binding to the diferrous site.
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| 4. |
- Cosquer, Guirec Y., Wang J., Naeslund C., Adams D.M., Ji W., Zhuo J-C., Anisuzzaman A.K.M.,Sjöberg S., Barth R.F., Eriksson S., Tjarks W.
(författare)
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Synthesis and biological evaluation of carboranyl thymidines for BNTC
- 2001
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Ingår i: 221st MEDI-151. - : Abstr Pap Am Chem Soc. ; , s. 151-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
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| 8. |
- Pan, M., et al.
(författare)
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An analysis of the Ethiopian Rift Valley GPS campaigns in 1994 and 1999
- 2002
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Ingår i: Journal of Geodynamics. - 0264-3707 .- 1879-1670. ; 33:3, s. 333-343
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Tidskriftsartikel (refereegranskat)abstract
- In cooperation with the Geophysical Observatory, Addis Ababa University, the Department of Geodesy and Photogrammetry of the Royal Institute of Technology carried out GPS measurements at three deformation networks in the Ethiopian Rift Valley in 1994 and 1999. For these campaigns the session-to-session repeatabilities were about 5 and 4 mm in the horizontal components and 50 and 10 mm in the vertical components using the IGS precise orbits, respectively. The results show, that the stations of the E3 network in the Rift Valley moved with a magnitude of 2.5 +/- 1.3 mm/a to the SE, and a magnitude of 21.3 +/- 1.4 mm/a to the ENE in the northeast (close to Assab of the Red Sea) relative to the station Addis Ababa on the African plate. The direction of movement is consistent with the local spreading vector of the Red Sea Rift with the N84degreesE slip direction estimated from seismic data. The sites of the E1 network moved by a rate of about 1-2 mm/a to the SE relative also to the station Addis Ababa. Further to the south there is an indication from our GPS data that the stations on the Somalian plate of the E2 network move by a rate of about 2.5 mm/a to the E or SE relative to the African plate. This motion can also be confirmed by geological and geodynamic data.
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| 10. |
- Brederlau, Anke, 1968, et al.
(författare)
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The bone morphogenetic protein type Ib receptor is a major mediator of glial differentiation and cell survival in adult hippocampal progenitor cell culture.
- 2004
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Ingår i: Molecular biology of the cell. - 1059-1524. ; 15:8, s. 3863-75
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Tidskriftsartikel (refereegranskat)abstract
- Bone morphogenetic proteins (BMPs) act as growth regulators and inducers of differentiation. They transduce their signal via three different type I receptors, termed activin receptor-like kinase 2 (Alk2), Alk3, or bone morphogenetic protein receptor Ia (BMPRIa) and Alk6 or BMPRIb. Little is known about functional differences between the three type I receptors. Here, we have investigated consequences of constitutively active (ca) and dominant negative (dn) type I receptor overexpression in adult-derived hippocampal progenitor cells (AHPs). The dn receptors have a nonfunctional intracellular but functional extracellular domain. They thus trap BMPs that are endogenously produced by AHPs. We found that effects obtained by overexpression of dnAlk2 and dnAlk6 were similar, suggesting similar ligand binding patterns for these receptors. Thus, cell survival was decreased, glial fibrillary acidic protein (GFAP) expression was reduced, whereas the number of oligodendrocytes increased. No effect on neuronal differentiation was seen. Whereas the expression of Alk2 and Alk3 mRNA remained unchanged, the Alk6 mRNA was induced after impaired BMP signaling. After dnAlk3 overexpression, cell survival and astroglial differentiation increased in parallel to augmented Alk6 receptor signaling. We conclude that endogenous BMPs mediate cell survival, astroglial differentiation and the suppression of oligodendrocytic cell fate mainly via the Alk6 receptor in AHP culture.
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