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- Behravan, G, et al.
(författare)
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Expression, purification and characterization of the homeodomain of rat ISL-1 protein.
- 1997
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Ingår i: Protein Engineering. - 0269-2139 .- 1460-213X. ; 10:11, s. 1327-31
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Tidskriftsartikel (refereegranskat)abstract
- Isl-1 is a member of a family of Homeodomains containing proteins that possess an N-terminal pair of zinc binding LIM domains. The Isl-1 gene in rat codes for a protein that binds to the insulin gene enhancer and is also involved in regulation of amylin and proglucagon genes. A DNA sequence coding for 66 amino acid residues containing the C-terminal homeodomain fragment of Isl-1 was expressed as a soluble protein in Escherichia coli. Here, we describe a procedure which allows the rapid native purification of recombinant homeodomain protein fused to an N-terminal tag of six histidines. The purified homeodomain showed DNA-binding activity to its cognate DNA sequence. An enhanced binding activity is observed in the presence of a reducing agent in electrophoretic mobility shift assays. The DNA binding was further characterized by circular dichroism spectroscopy. Addition of DNA to the homeodomain did not change the overall secondary structure content, but the thermal and chemical denaturing profiles were altered. A stabilization of the secondary structure was observed upon DNA binding. The free energy of unfolding at 23 degrees C was 7 kJ mol(-1) in absence of DNA and 29 kJ mol(-1) in the presence of DNA.
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- Lycksell, P O, et al.
(författare)
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Sequence specific 1H-NMR assignments and secondary structure of a carboxy-terminal functional fragment of apolipoprotein CII.
- 1992
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Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 205:1
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Tidskriftsartikel (refereegranskat)abstract
- The structural properties of a synthetic fragment of human apolipoprotein CII (apoCII) has been studied by circular dichroism and proton nuclear magnetic resonance. The fragment corresponds to the carboxy-terminal 30 amino acid residues and retains the ability of apoCII to activate lipoprotein lipase. Like native apoCII, the fragment has a tendency to self-associate in pure aqueous solution. Addition of 1,1,1,3,3,3-hexafluoro-2-isopropanol to aqueous solvent dissolves the aggregates and leads to an increase in the alpha-helical content of the peptide, probably by stabilizing transient helical structures. The resonances in the 1H-NMR spectrum of the fragment in 35% (CF3)2CHOH were assigned through standard procedures from nuclear Overhauser enhancement spectroscopy, correlated spectroscopy and total correlated spectroscopy experiments. The NMR data indicates the formation of a stable alpha helix spanning Ile66-Gly77. Another alpha helical turn may be formed between Lys55 and Ala59 and possibly span even further towards the carboxyl terminus. These structural elements are different from those previously predicted for this part of the sequence of apoCII.
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- Zegar, I., et al.
(författare)
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The B - Z Transition in Poly [d(G-C) d(G-C)] After Covalent Binding of Anti- Benzo(a)Pyrenediolepoxide
- 1987
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Ingår i: Structure, dynamics, and function of biomolecules : the first EBSA workshop, a Marcus Wallenberg symposium (Structure, dynamics, and function of biomolecules : the first EBSA workshop, a Marcus Wallenberg symposium /Structure, dynamics, and function of biomolecules : the first EBSA workshop, a Marcus Wallenberg symposium Structure, dynamics, and function of biomolecules : the first EBSA workshop, a Marcus Wallenberg symposium (A. Ehrenberg, R. Rigler, A. Gräslund and L. Nilsson, eds.). - 3540172793 ; , s. 238-241
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 17. |
- Öhman, Anders, et al.
(författare)
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A refined three-dimensional solution structure of a carboxy terminal fragment of apolipoprotein CII.
- 1993
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Ingår i: European Biophysics Journal. - 0175-7571 .- 1432-1017. ; 22:5
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Tidskriftsartikel (refereegranskat)abstract
- The three-dimensional structure of a synthetic fragment of human apolipoprotein CII (apo-CII) in 35%, 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) has been determined on the basis of distance and intensity constraints derived from two-dimensional proton nuclear magnetic resonance measurements. The NOE crosspeak build-up rates were converted to distance constraints which were used in the distance geometry program DI-ANA. A set of one hundred structures were generated and of these ten structures were used in molecular dynamics simulations using the program XPLOR. This program enabled a direct minimization between the difference of the two-dimensional NOE intensities and those calculated from the full relaxation matrix. In this way spin diffusion is fully taken into account, which can be seen from the considerable improvement of the R-factor after the relaxation matrix refinement. These calculations show that this fragment, which corresponds to the carboxy terminal 30 amino acids of intact apo-CII and which retains its ability to activate lipoprotein lipase, is essentially flexible, but has three defined secondary structural elements. The most significant one is an alpha-helix between residues 67 and 74. The following three residues adopt a turn-like structure. Another turn of alpha-helix is seen between residues 56 and 59. The effect of the solvent system on the secondary structure was studied by circular dichroism spectroscopy. The results show that the mixed aqueous 35% HFP solvent induces secondary structure of a very similar nature to the one induced by sodium dodecyl sulphate.
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| 18. |
- Öhman, Anders, et al.
(författare)
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NMR study of the conformation and localization of porcine galanin in SDS micelles. Comparison with an inactive analog and a galanin receptor antagonist.
- 1998
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 37:25
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Tidskriftsartikel (refereegranskat)abstract
- Galanin is a 29/30-residue neuro-endocrine peptide which performs its many important physiological functions via a membrane-bound receptor. By using two-dimensional proton NMR spectroscopy, complete relaxation matrix analysis, and simulated annealing, the conformation of porcine galanin was determined in a membrane-mimicking solvent containing sodium dodecyl sulfate (SDS) micelles. The final family of calculated structures displays three well-defined beta- or gamma-turn regions, comprising residues 1-5, 7-10, and 24-27, but has otherwise a random conformation. The receptor-interacting N-terminal part, residues 1-5, was found to be best defined with a backbone RMSD value of 0.12 A. The mode of association between galanin and the SDS micelle was determined by observing the broadening effect on proton resonances, when spin-labeled 5- and 12-doxyl stearate molecules were added. It was concluded that galanin is located close to the surface of the micelle with two regions, residues 6-9 and 24-29, as well as two single residues, 18 and 21, reaching out into the aqueous solvent. Additional NMR studies were carried out on an inactive analogue, Ala2-galanin, and an antagonist M40. The results show that the proton resonances of galanin and M40 have identical chemical shifts in the N-terminal receptor-interacting region, indicating similar solution structures in this region. For Ala2-galanin, the same region displays a spectral heterogeneity with chemical shifts clearly different from the other two peptides, indicative of different secondary structures. These results may provide a structural background for the antagonist activity of M40 and the hormonal inactivity of Ala2-galanin, as compared to galanin.
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| 19. |
- Öhman, Anders, et al.
(författare)
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Solvent stabilized solution structures of galanin and galanin analogs, studied by circular dichroism spectroscopy.
- 1995
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Ingår i: Biochimica et Biophysica Acta. - 0006-3002 .- 1878-2434. ; 1236:2
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Tidskriftsartikel (refereegranskat)abstract
- Circular dichroism spectroscopy has been used to study how different solvents stabilize secondary structure in the neuropeptide galanin (rat), two N-terminal fragments of galanin, galanin(1-12) and galanin(1-16), and six other differently charged analogs. Among these analogs, the peptide M40, galanin(1-13)-Pro-Pro-Ala-Leu-Ala-Leu-Ala amide, is a high affinity, receptor subtype specific galanin receptor antagonist. The different solvents include sodium dodecyl sulfate (SDS) micelle solutions, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphoglycerol (DOPG) vesicle solutions. 100% 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) and 100% 2,2,2-trifluoroethanol (TFE). DOPC vesicles did not change the structure of the peptides as compared to aqueous solvent. The negatively charged DOPG vesicles and SDS micelles induced similar changes towards alpha-helical structures in all peptides. The HFP and TFE solvents have an even stronger tendency to stabilize alpha-helical conformations in these peptides. Since DOPG vesicles can be considered as a model system for negatively charged biological membranes, the solution structures observed in the presence of DOPG or SDS may be the most relevant for the in vivo situation. Correlations between the binding affinity of the peptides to hippocampal galanin receptors and their observed structures in the DOPG solvent were investigated.
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