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  • 2000-2004  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Structure of rat transthyretin (rTTR) complex with thyroxine at 2.5 Å resolution: first non-biased insight into thyroxine binding reveals different hormone orientation in two binding sites (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1061-1070 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The first observation of the unique environment for thyroxine (T4) binding in tetrameric rat transthyretin (rTTR) is reported as determined by X-ray diffraction. These data revealed different modes of hormone binding in the two unique hormone-binding sites in the rat TTR tetramer channel. Differences in the orientation of thyroxine and the position of water molecules in the two binding sites further suggest a mechanism for the docking pathway of the hormone into the channel of TTR. Crystals of the rat transthyretin–thyroxine complex are isomorphous with those reported for apo rTTR and crystallized in the tetragonal space group P43212 with four independent TTR monomeric subunits in the asymmetric part of the crystal lattice. Data were collected to 2.5 Å resolution and the structure was refined to R = 20.9% for 15 384 data in the resolution range 12–2.5 Å. Similar to human TTR, the rat protein is also a 54 000 Da tetramer with four identical polypeptide chains of 127 amino-acid residues. Of the 22 amino-acid residues which differ between the human and rat sequences, none are in the thyroxine-binding domains. Analysis of these structural data reveals that the tertiary structure is similar to that of hTTR, with only small differences in the flexible loop regions on the surface of the structure. Conformational changes of the amino acids in the channel result in a hydrogen-bonded network that connects the two binding domains, in contrast to the hydrogen bonds formed along the tetramer interface in the apo transthyretin structure. These changes suggest a mechanism for the signal transmission between thyroxine-binding domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444901007235
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Structure of the insecticidal bacterial δ-endotoxin Cry3Bb1 of Bacillus thuringiensis (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1101-1109 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The coleopteran-active δ-endotoxin Cry3Bb1 from Bacillus thuringiensis (Bt) strain EG7231 is uniquely toxic to Diabrotica undecimpunctata, the Southern corn rootworm, while retaining activity against Leptinotarsa decemlineata, the Colorado potato beetle. The crystal structure of the δ-endotoxin Cry3Bb1 has been refined using data collected to 2.4 Å resolution, with a residual R factor of 17.5% and an Rfree of 25.3%. The structure is made up of three domains: I, a seven-helix bundle (residues 64–294); II, a three-sheet domain (residues 295–502); and III, a β-sandwich domain (residues 503–652). The monomers in the orthorhombic C2221 crystal lattice form a dimeric quaternary structure across a crystallographic twofold axis, with a channel formed involving interactions between domains I and III. There are 23 hydrogen bonds between the two monomers conferring structural stability on the dimer. It has been demonstrated that Cry3Bb1 and the similar toxin Cry3A form oligomers in solution. The structural results presented here indicate that the interactions between domains I and III could be responsible for the initial higher order structure and have implications for the biological activity of these toxins. There are seven additional single amino-acid residues in the sequence of Cry3Bb1 compared with that of Cry3A; one in domain I, two in domain II and four in domain III, which also shows the largest conformational difference between the two proteins. These changes can be implicated in the selectivity differences noted for these two δ-endotoxins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444901008186
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Structure of a new polymorphic monoclinic form of human transthyretin at 3 Å resolution reveals a mixed complex between unliganded and T4-bound tetramers of TTR (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 957-967 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of a new polymorphic form of human transthyretin (hTTR) with a lattice containing a unique assembly of apo hTTR and TTR–T4 complex has been determined to 3 Å resolution. The monoclinic form of human TTR reported here crystallizes in space group P21, with unit-cell parameters a = 76.7 (6), b = 96.7 (8), c = 81.7 (4) Å, β = 106.8 (4)°. The asymmetric unit contains two tetramers of transthyretin related by the non-crystallographic symmetry (NCS) operation of a 90.28° rotation between two hTTR molecules around an axis close to crystallographic z. The r.m.s. difference between the two tetramers calculated from their Cα positions is 0.48 Å. The structure was refined using 15.0–3.0 Å resolution data to R = 22.9% and Rfree = 28.9% for reflections F 〉 0.0σ(F), and R = 19.7% and Rfree = 25.8% for reflections F 〉 3.0σ(F). The intermolecular interactions involve the tips of α-helices and loops around Arg21, Glu61 and Ser100 of all monomers. The electron-density maps revealed residual thyroxine (T4) bound in only one of the two unique tetrameric TTR molecules, with an occupancy of 53%, while the second tetramer is unliganded. One thyroxine ligand is bound in a way similar to the orientations described for the orthorhombic form of the hTTR–T4 complex. The T4 bound in the second site is positioned similar to 3′,5′-dinitro-N-acetyl-L-thyronine in its hTTR complex. Differences in the size of the central channel defined by the D, A, G and H β-strands of two monomeric subunits are observed between the apo TTR and T4-bound tetramer. The averaged distances between Ala108 Cα and its equivalent measured across each binding site are 12.34 Å for the T4-bound and 10.96 Å for the unliganded TTR tetramer, respectively. The observed differences might reflect the mechanics of the ligand binding in the channel and possibly explain the observed negative cooperativity effect for ligand binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444901006047
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    Paper (German National Licenses)
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