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  • 1
    Electronic Resource
    Electronic Resource
    Functional roles of amino acid residues involved in forming the α-helix-turn-α-helix operator DNA binding motif of tet represser from Tn10 (1992)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 168-177 
    Details
    ISSN: 0887-3585
    Keywords: protein structure ; helix-turn-helix motif ; Tet represser ; mutagenesis ; structure predictions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The Tn10derived Tet represser contains an amino acid segment with high homology to the α-helix-turn-α-helix motif (HTH) of other DNA binding proteins. The five most conserved amino acids in HTH are probably involved in structural formation of the motif. Their functional role was probed by saturation mutagenesis yielding 95 single amino acid replacement mutants of Tet repressor. Their binding efficiencies to tet operator were quantitatively determined in vivo. All functional mutants contain amino acid substitutions consistent with their proposed role in a HTH. In particular, only the two smallest amino acids (serine, glycine) can substitute a conserved alanine in the proposed first α-helix without loss of activity. The last position of the first α-helix, the second position in the turn, and the fourth position in the second α-helix require mostly hydrophobic residues. The proposed C-terminus of the first α-helix is supported by a more active asparagine compared to glutamine replacement mutant of the wt leucine residue. The turn is located close to the protein surface as indicated by functional lysine and arginine replacements for valine. A glycine residue at the first position in the turn can be replaced by any amino acid yielding mutants with at least residual tet operator affinity. A structural model of the HTH of Tet repressor is presented. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340140204
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  • 2
    Electronic Resource
    Electronic Resource
    βVI Turns in peptides and proteins: A model peptide mimicry (1993)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 15 (1993), S. 235-251 
    Details
    ISSN: 0887-3585
    Keywords: conformational analysis ; 2D NMR spectroscopy ; restrained molecular dynamics ; RGD peptides ; proline ; cis/trans isomerism ; peptide templates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: To investigate the role of proline in defining β turn conformations within cyclic hexa- and pentapeptides we synthesized and determined the conformations of a series of L- and D-proline-containing peptides by means of 2D NMR spectroscopy and restrained molecular dynamics simulations. Due to cis/trans isomerism the L-proline peptides adopt at least two different conformations that are analyzed and compared to the structures of the corresponding D-proline peptides. The cis conformations of the compounds cyclo(-Pro-Ala-Ala-Pro-Ala-Ala-), cyclo(-Arg-Gly-Asp-Phe-Pro-Gly-), cyclo(-Arg-Gly-Asp-Phe-Pro-Ala-), cyclo(-Pro-Ala-Ala-Ala-Ala--), and cyclo(-Pro-Ala-Pro-Ala-Ala-) form uncommon βVI turns that mimic the turn geometries found in crystallographically refined protein structures at such a detailed level that even preferred side chain orientations are reproduced. The ratios of the cis/trans isomers are analyzed in terms of the steric demand of the proline-following residue. The conformational details derived from this study illustrate the importance of the examination of small model compounds derived from protein loop regions, especially if bioactive recognition sequences, such as RGD (Arg-Gly-Asp), are incorporated. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340150303
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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