| 1. |
- Carlsson, Christina, 1968, et al.
(författare)
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Screening for genetic mutations
- 1996
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 380:6571, s. 207-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Ellouze, C., et al.
(författare)
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Difference between active and inactive nucleotide cofactors in the effect of DNA binding and the helical structure of RecA filament
- 1999
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 262:1, s. 88-94
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Tidskriftsartikel (refereegranskat)abstract
- The RecA protein requires ATP or dATP for its coprotease and strand exchange activities. Other natural nucleotides, such as ADP, CTP, GTP, UTP and TTP, have little or no activation effect on RecA for these activities. We have investigated the activation mechanism, and the selectivity for ATP, by studying the effect of various nucleotides on the DNA binding and the helical structure of the RecA filament. The interaction with DNA was investigated via fluorescence measurements with a fluorescent DNA analog and fluorescein-labeled oligonucleotides, assisted by linear dichroism. Filament structure was investigated via small-angle neutron scattering. There is no simple correlation between filament elongation, DNA binding affinity of RecA, and DNA structure in the RecA complex. There may be multiple conformations of RecA, Both coprotease and strand exchange activities require formation of a rigid and well organized complex. The triphosphate nucleotides which do not activate RecA, destabilize the RecA-DNA complex, indicating that the chemical nature of the nucleotide nucleobase is very important for the stability of RecA-DNA complex. Higher stability of the RecA-DNA complex in the presence of adenosine 5'-O-3-thiotriphosphate or guanosine 5'-O-3-thiotriphosphate than ATP or GTP indicates that contact between the protein and the chemical group at the gamma position of the nucleotide also affects the stability of the RecA-DNA complex. This contact appears also important for the rigid organization of DNA because ADP strongly decreases the rigidity of the complex.
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| 3. |
- Ellouze, C., et al.
(författare)
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Nucleotide Cofactor-Dependent Structural Change of Xenopus laevis Rad51 Protein Filament Detected by Small-Angle Neutron Scattering Measurements in Solution
- 1997
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 36:44, s. 13524-13529
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Tidskriftsartikel (refereegranskat)abstract
- Rad51 protein, a eukaryotic homologue of RecA protein, forms a filamentous complex with DNA and catalyzes homologous recombination. We have analyzed the structure of Xenopus Rad51 protein (XRad51.1) in solution by small-angle neutron scattering (SANS). The measurements showed that XRad51.1 forms a helical filament independently of DNA. The sizes of the cross-sectional and helical pitch of the filament could be determined, respectively, from a Guinier plot and the position of the subsidiary maximum of SANS data. We observed that the helical structure is modified by nucleotide binding as in the case of RecA. Upon ATP binding under high-salt conditions (600 mM NaCl), the helical pitch of XRad51.1 filament was increased from 8 to 10 nm and the cross-sectional diameter decreased from 7 to 6 nm. The pitch sizes of XRad51.1 are similar to, though slightly larger than, those of RecA filament under corresponding conditions. A similar helical pitch size was observed by electron microscopy for budding yeast Rad51 [Ogawa, T., et al. (1993) Science 259, 1896-1899]. In contrast to the RecA filament, the structure of XRad51.1 filament with ADP is not significantly different from that with ATP. Thus, the hydrolysis of ATP to ADP does not modify the helical filament of XRad51.1. Together with our recent observation that ADP does not weaken the XRad51.1/DNA interaction, the effect of ATP hydrolysis on XRad51.1 nucleofilament should be very different from that on RecA.
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| 4. |
- Eriksson, Svante, 1957, et al.
(författare)
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ROLE OF TYROSINE RESIDUE-264 OF RECA FOR THE BINDING OF COFACTOR AND DNA
- 1993
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 268:3, s. 1811-1816
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Tidskriftsartikel (refereegranskat)abstract
- The tyrosine fluorescence of the RecA protein is quenched by about 15% upon binding of the cofactor analog adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS). This quenching is not observed with a modified RecA in which the tyrosine residue at position 264 (Tyr-264) is replaced for alanine by site-directed mutagenesis, a modification which also results in a decrease of binding affinity of cofactor. This indicates that Tyr-264 is responsible for the fluorescence change and that the residue is close to or within the cofactor binding site. Upon DNA binding, a change of tyrosine fluorescence is observed both with the modified protein and with wild type RecA, indicating that DNA binding affects the environment of other tyrosine residues than Tyr-264. However, the change is significantly smaller in the modified protein, suggesting that both Tyr-264 as well as other residue(s) may be affected by the DNA binding. Changed fluorescence properties of the remaining tyrosine residues as a result of a slightly different DNA binding mode of the modified protein are also possible. Tyr-264 may be an important residue for the allosteric effect induced by the cofactor for the binding of DNA to RecA. In the recent crystal structure of RecA-ADP published by Story and Steitz (Story, R. M., and Steitz, T. A. (1992) Nature 355, 374-376), ADP is stacked with Tyr-103 and does not interact with Tyr-264. The fact that we observe no interaction of ATPgammaS with Tyr-103 (as evidenced from absence of fluorescence change) but instead with Tyr-264 may suggest an important conformational difference between the RecA complexes with, respectively, ADP and ATP.
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| 5. |
- Kim, S.K., et al.
(författare)
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Binding Geometries of Triple Helix Selective Benzopyrido [4,3-b]indole Ligands Complexed with Double- and Triple-Helical Polynucleotides
- 1997
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Ingår i: Biopolymers. - 0006-3525 .- 1097-0282. ; 42:1, s. 101-111
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Tidskriftsartikel (refereegranskat)abstract
- The binding modes of three benzopyrido[4,3-b]indole derivatives (and one benzo[f]pyrido[4-3b]quinoxaline derivative) with respect to double helical poly(dA) . poly(dT) and poly[d(A-T)](2) and triple-helical poly(dA) . 2poly(dT) have been investigated using linear dichroism (LD) and CD: (I) 3-methoxy-11-amino-BePI where BePI = {7H-8-methyl-benzo[e]pyrido[4,3-b]indole}, (II) 3-methoxy-11-[(3'-amino)propylamino]-BePI, (III) 3-methoxy-7-[(3'diethylamino)propylamino]BgPI where BgPI = {benzo[g]pyrido[4,3-b]indole}, and (IV) 3-methoxy-11-[(3'amino)propylamino]BfPQ where BfPQ = {benzo[f]pyrido[4-3b]quinoxaline}. The magnitudes of the reduced LD of the electronic transitions of the polynucleotide bases and of the bound ligands are generally very similar, suggesting an orientation of the plane of the ligands' fused-ring systems preferentially perpendicular to the helix axis. The LD results suggest that all of the ligands are intercalated for all three polynucleotides. The induced CD spectrum of the BePI chromophore in the (II-BePI)-poly[d(A-T)](2) complex is almost a mirror image of that for the (I-BePI)-poly(dA) . poly(dT) and (I-BePI)-poly(dA) . 2poly(dT) complexes, suggesting an antisymmetric orientation of the BePI moiety upon intercalation in poly[d(A-T)]2 compared to the other polynucleotides. The induced CD of I-BePI bound to poly(dA) . 2poly(dT) suggests a geometry that is intermediate between that of its other two complexes. The concluded intercalative binding as well as the conformational variations between the different BePI complexes are of interest in relation to the fact that BePI derivatives are triplex stabilizers.
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| 6. |
- Koch, T., et al.
(författare)
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PNA-Peptide Chimerae
- 1995
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1873-3581. ; 36:38, s. 6933-6936
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Tidskriftsartikel (refereegranskat)abstract
- Radioactive labelling of PNA has been performed try linking a peptide segment to the PNA which is substrate for protein kinase A. The enzymatic phosphorylation proceeds in almost quantitative yields.
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| 7. |
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| 8. |
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| 9. |
- Morimatsu, K., et al.
(författare)
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Roles of Tyr103 and Tyr264 in the regulation of RecA-DNA interactions by nucleotide cofactors
- 1996
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 240:1, s. 91-97
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Tidskriftsartikel (refereegranskat)abstract
- The DNA-binding mode of the RecA protein, in particular its dependence on nucleotide cofactor, has been investigated by monitoring the fluorescence and linear-dichroism signals of a tryptophan residue inserted in the RecA to replace tyrosine at position 103 or 264. These residues are important for cofactor and DNA binding, as evidenced from their fluorescence changes upon binding of cofactor and DNA [Morimatsu, K., Horii, T, & Takahashi, M. (1995) Eur. J. Biochem. 228, 779-785]. The substitution of these residues with tryptophan does not affect the structure or biological function of the complex and can therefore be exploited to gain structural information in terms of the orientation and environment of the inserted reporter chromophore. The fluorescence change upon formation of the ternary cofactor . RecA . DNA complex was much smaller than the sum of the changes induced by cofactor or DNA alone, This difference indicates that the cofactor and DNA interact with RecA via common components. The fluorescence change caused by DNA in the presence of cofactor was almost independent of the base composition of DNA, in contrast to the interaction in the absence of cofactor. Hence, the contact mode between the selected residues and DNA in the complex may depend significantly on the cofactor, Linear-dichroism measurements indicate that the cofactor does not markedly alter the organization of RecA filament. Linear dichroism shows that neither the aromatic moiety of residue 103 nor that of residue 264 is intercalated between the DNA bases. The textural changes reported for the helical pitch and contour length of RecA fiber upon interaction with cofactor and DNA may derive from a subtle change in orientation of the RecA subunits in the filament.
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| 10. |
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| 11. |
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| 12. |
- Nordén, Bengt, 1945, et al.
(författare)
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X-POLARIZED AND Y-POLARIZED SPECTRA OF CHLOROPHYLL-A AND PHEOPHYTIN-A IN THE RED REGION - RESOLUTION ENHANCEMENT AND GAUSSIAN DECONVOLUTION
- 1992
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Ingår i: Australian Journal of Chemistry. - : CSIRO Publishing. - 1445-0038 .- 0004-9425. ; 45:10, s. 1559-1570
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Tidskriftsartikel (refereegranskat)abstract
- The red region of the X- and Y-polarized spectra obtained from the measurement of linear dichroism of chlorophyll a and pheophytin a oriented in a liquid crystal1 has been reexamined. A combination of resolution enhancement of the spectra involving their Fourier transformation and manipulation in the Fourier domain, and deconvolution into Gaussian bands on the wavenumber scale has produced results conforming to previous conclusions that place the origin of the Q(X) transition in chlorophyll a some 800-900 cm-1 to the blue relative to the origin of the Q(Y) transition. In pheophytin a, however, the separation between the Q(X) and Q(Y) bands is much larger, about 3600 cm-1. The results also confirm previous reports of an angle near 70-degrees between the transition moment directions of the Q(Y) transitions and the molecular X-axis for both chlorophyll a and pheophytin a. The resolved vibronic bands in the case of the Q(Y) transition of chlorophyll a, at least, have their counterparts in both solution spectra and high-resolution low-temperature fluorescence excitation spectra.
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| 13. |
- Nordén, T, et al.
(författare)
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Mammographic screening for breast cancer : What cancers do we find?
- 1997
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Ingår i: European Journal of Cancer. - : Elsevier. - 0959-8049 .- 1879-0852. ; 33:4, s. 624-628
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare lymph node involvement of breast cancer cases detected at mammography screening with clinically-detected cases. During a 3-year period, 273 primary breast cancers were detected in a population-based screening programme, and 149 primary breast cancers were diagnosed clinically. Lymph node involvement was evaluated in univariate and multivariate logistic regression models correcting for tumour size, histological grade, steroid receptor status and DNA-ploidy. Patients with screen-detected cancers had a low relative risk of having lymph node metastases (univariate, OR = 0.31; 95% confidence interval = 0.19-0.52). In the multivariate logistic regression model, the relative risk was halved (OR = 0.47; 0.28-0.78). The reduced risk was more pronounced for women younger than 50 years of age compared to older women. The risk for screen-detected cases of having lymph node metastases at diagnosis was statistically significantly lower than for clinically-detected cases. The marked reduction, even when correcting for tumour size, makes it less likely that factors such as detection of clinically innocent tumours, length bias sampling or clinical symptoms related to axillary metastases can explain the whole difference. The results indicate at least part of the effect may be explained by tumour progression in the late preclinical detectable phase.
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| 14. |
- Norden, T, et al.
(författare)
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Mammographic screening for breast cancer. What cancers do we find?
- 1997
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Ingår i: EUROPEAN JOURNAL OF CANCER. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0959-8049. ; 33:4, s. 624-628
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare lymph node involvement of breast cancer cases detected at mammography screening with clinically-detected cases. During a 3-year period, 273 primary breast cancers were detected in a population-based screening programme
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| 15. |
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| 16. |
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| 17. |
- Saalman, Elisabeth, 1955, et al.
(författare)
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EFFECT OF 2.45 GHZ MICROWAVE-RADIATION ON PERMEABILITY OF UNILAMELLAR LIPOSOMES TO 5(6)-CARBOXYFLUORESCEIN - EVIDENCE OF NONTHERMAL LEAKAGE
- 1991
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Ingår i: Biochimica Et Biophysica Acta. - : Elsevier BV. - 0006-3002 .- 0005-2736. ; 1064:1, s. 124-130
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Tidskriftsartikel (refereegranskat)abstract
- The influence of 2.45 GHz microwave radiation on the membrane permeability of unilamellar liposomes was studied using the marker 5(6)-carboxyfluorescein trapped in phosphatidylcholine liposomes. The release of the fluorescent marker was followed by spectrofluorimetry after an exposure of 10 minutes to either microwave radiation or to heat alone of the liposome solutions. A significant increase of the permeability of carboxyfluorescein through the membrane was observed for the microwave-exposed samples compared to those exposed to normal heating only. Exposure to 2.45 GHz microwave radiation of liposomes has been previously found to produce increased membrane permeability as compared with heating. However, in contrast to previous studies, the observations reported here were made above the phase transition temperature of the lipid membrane. The experimental setup included monitoring of the temperature during microwave exposure simultaneously at several points in the solution volume using a fiberoptic thermometer. Possible mechanisms to explain the observations are discussed.
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| 18. |
- Selmane, T., et al.
(författare)
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The L2 Loop Peptide of recA Stiffens and restricts Base Motions of Single-stranded DNA Similar to Intact Protein
- 1999
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Ingår i: FEBS Letters. - 1873-3468 .- 0014-5793. ; 446:1, s. 30-34
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Tidskriftsartikel (refereegranskat)abstract
- The L2 loop in the RecA protein is the catalytic center for DNA strand exchange, Here we investigate the DMA binding properties of the L2 loop peptide using optical spectroscopy with polarized light. Both fluorescence intensity and anisotropy of an etheno-modified poly(dA) increase upon peptide binding, indicate that the base motions of single-stranded DNA are restricted in the complex. In agreement with this conclusion, the peptide-poly(dT) complex exhibits a significant linear dichroism signal. The peptide is also found to modify the structure of double-stranded DNA, but does not denature it. It is inferred that strand separation may not be required for the formation of a joint molecule.
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