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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biomolecular NMR 15 (1999), S. 39-53 
    ISSN: 1573-5001
    Keywords: asymmetry ; homotetramer ; inter-subunit NOE ; protein structure ; slow chemical exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The structure and dynamics of the chymotryptic tetramerization domain of the Mnt repressor of Salmonella bacteriophage P22 have been studied by NMR spectroscopy. Two sets of resonances (A and B) were found, representing the asymmetry within the homotetramer. Triple-resonance techniques were used to obtain unambiguous assignments of the A and B resonances. Intra-monomeric NOEs, which were distinguished from the inter-monomeric NOEs by exploiting 13C/15N-filtered NOE experiments, demonstrated a continuous α-helix of approximately seven turns for both the A and B monomers. The asymmetry facilitated the interpretation of inter-subunit NOEs, whereas the antiparallel alignment of the subunits allowed further discrimination of inter-monomeric NOEs. The three-dimensional structure revealed an unusual asymmetric packing of a dimer of two antiparallel right-handed intertwined coiled α-helices. The A and B forms exchange on a timescale of seconds by a mechanism that probably involves a relative sliding of the two coiled coils. The amide proton solvent exchange rates demonstrate a stable tetrameric structure. The essential role of Tyr 78 in oligomerization of Mnt, found by previous mutagenesis studies, can be explained by the many hydrophobic and hydrogen bonding interactions that this residue participates in with adjacent monomers.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 242 (1994), S. 237-240 
    ISSN: 1617-4623
    Keywords: Selective protein degradation ; prc (tsp) deletion strain ; Carboxyl terminus ; λ repressor ; Escherichia coli K-12
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Escherichia coli protease Prc (Tsp) exhibits specificity in vitro for proteins with nonpolar carboxyl termini. To determine whether Prc is responsible for the selective degradation in vivo of proteins with nonpolar carboxyl termini, we constructed a prc (tsp) deletion strain. Deletion of the prc gene did not prevent the rapid intracellular degradation of a variant of the amino-terminal domain of λ repressor with a nonpolar carboxyl terminus, even though this protein is a substrate for Prc in vitro. Our results indicate that at least one additional carboxy-terminal-specific proteolytic system must exist in E. coli.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: mutant proteins ; protein stability ; operator binding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We have isolated 64 different missense mutations at 36 out of 53 residue positions in the Arc repressor of bacteriophage P22. Many of the mutant proteins with substitutions in the C-terminal 40 residues of Arc have reduced intracellular levels and probably have altered structures or stabilities. Mutations in the N-terminal ten residues of Arc cause large decreases in operator DNA binding affinity without affecting the ability of Arc to fold into a stable three-dimensional structure. We argue that these N-terminal residues are important for operator recognition but that they are not part of a conventional helix-turn-helix DNA binding structure. These results suggest that Arc may use a new mechanism for sequence specific DNA binding.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural & molecular biology 12 (2005), S. 520-525 
    ISSN: 1545-9985
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Energy-dependent proteases often rely on adaptor proteins to modulate substrate recognition. The SspB adaptor binds peptide sequences in the stress-response regulator RseA and in ssrA-tagged proteins and delivers these molecules to the AAA+ ClpXP protease for degradation. The structure of SspB ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature structural & molecular biology 11 (2004), S. 800-802 
    ISSN: 1545-9985
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Cells use elaborate transcriptional and translational mechanisms to control the timing and fidelity of protein synthesis. It is becoming increasingly apparent that intricate mechanisms also control how and when specific proteins are removed by degradation. Energy-dependent proteolytic machines ...
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 29 (1985), S. 217-224 
    ISSN: 0730-2312
    Keywords: mutant repressors ; differential scanning calorimetry ; protein stability ; thermal denaturation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The thermal denaturations of five revertant λ repressors containing single amino acid substitutions in their N-terminal domains have been studied by differential scanning calorimetry. Two substitutions slightly decrease stability, and the remaining three render the protein more stable than wild type. The Gly48 → Asn and Gly48 → Ser proteins are 4°C more stable than wild type. These two substitutions replace an α helical residue, and in each case a poor helix forming residue, glycine, is replaced by a residue with a higher helical propensity. We also present data showing that one revertant, Tyr22 → Phe, has reduced operator DNA binding affinity despite its enhanced stability.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: enhanced stability ; λCro ; genetic suppression ; intracellular proteolysis ; antibody screen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A mutant Cro protein, which bears the Ile-30→ Leu substitution, is thermally unstable and degraded more rapidly than wildtype Cro in vivo. Using an antibody screen, we have isolated five different second site suppressor substitutions that reduce the proteolytic hypersensitivity of this mutant Cro protein. Two of the suppressor substitutions increase the thermal stability of Cro by 12°C to 14°C. These amino acid substitutions affect residues 16 and 26, which are substitutions affect residues 16 and 26, which are substantially exposed to solvent in the crystal structure of wild-type Cro.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: protein families ; structure prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Hydrophobic side chains often are buried in the interior of a protein, and evolutionarily related proteins usually maintain the hydrophobic character of buried position. In this paper we shown that a pattern of hydrophobicity values derived from a set of related protein sequences is well correlated with the linear pattern of side-chain solvent accessibility values, calculated from a known protein structure representative of the sequences. In several cases, information from aligned sequences can be used to select the correct tertiary fold from a large database of protein structures.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: neutral mutations ; random mutagenesis ; protein structure ; protein folding ; protein families ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method of targeted random mutagenesis has been used in investigate the informational content of 25 residue positions in two α-helical regions of the N-terminal domain of λ repressor. Examination of the functionally allowed sequences indicates that there is a wide range in tolerance to amino acid substitution at these position. At position that are buried in the structure, there are severe limitations on the number and type of residues allowed. At most surface positions, many different residues and residue types are tolerated. However, at several surface positions there is a string preference for hydrophilic amino acids, and at one surface position proline is absolutely conserved. The results reveal the high level of degeneracy in the information that specifies a particular protein fold.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: protein stability ; helix-coil ; mutant ; calorimetry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Oligonucleotide-directed mutagenesis has been used to replace α-helical glycines in the N-terminal domain of λ repressor with alanines. Since alanine is a significantly better helix-forming residue than glycine, these changes were predicted to have a stabilizing effect. We show that the Gly46→Ala substitution, the Gly48→Ala substitution, and the double substitution increase the melting temperature of the N-terminal domain by 3-6°.
    Additional Material: 2 Ill.
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