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Buchumschlag von Functional roles of amino acid residues involved in forming the α–helix‐turn–α–helix operator DNA binding motif of tet represser from Tn10
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Functional roles of amino acid residues involved in forming the α–helix‐turn–α–helix operator DNA binding motif of tet represser from Tn10

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Zeitschriftentitel: Proteins: Structure, Function, and Bioinformatics
Personen und Körperschaften: Baumeister, Ralf, Müller, Gerhard, Hecht, Brigitte, Hillen, Wolfgang
In: Proteins: Structure, Function, and Bioinformatics, 14, 1992, 2, S. 168-177
Medientyp: E-Article
Sprache: Englisch
veröffentlicht:
Wiley
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Zusammenfassung: <jats:title>Abstract</jats:title><jats:p>The Tn<jats:italic>10</jats:italic>derived 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 <jats:italic>tet</jats:italic> 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.</jats:p>
Umfang: 168-177
ISSN: 0887-3585
1097-0134
DOI: 10.1002/prot.340140204