Environment-dependent long-range structural distortion in a temperature-sensitive point mutant

Jannette Carey, Brian Benoff, Balasubramanian Harish, Lara Yuan, Catherine L. Lawson

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Extensive environment-dependent rearrangement of the helix-turn-helix DNA recognition region and adjacent L-tryptophan binding pocket is reported in the crystal structure of dimeric E. coli trp aporepressor with point mutation Leu75Phe. In one of two subunits, the eight residues immediately C-terminal to the mutation are shifted forward in helical register by three positions, and the five following residues form an extrahelical loop accommodating the register shift. In contrast, the second subunit has wildtype-like conformation, as do both subunits in an isomorphous wildtype control structure. Treated together as an ensemble pair, the distorted and wildtype-like conformations of the mutant apoprotein agree more fully than either conformation alone with previously reported NOE measurements, and account more completely for its diverse biochemical and biophysical properties. The register-shifted segment Ile79-Ala80-Thr81-Ile82-Thr83 is helical in both conformations despite low helical propensity, suggesting an important structural role for the steric constraints imposed by β-branched residues in helical conformation. Published by Wiley-Blackwell.

Original languageEnglish (US)
Pages (from-to)63-74
Number of pages12
JournalProtein Science
Issue number1
StatePublished - Jan 2012

All Science Journal Classification (ASJC) codes

  • Molecular Biology
  • Biochemistry


  • Cooperativity
  • Crystal packing
  • Hydrophobic brace
  • ILV cluster
  • Rotamer


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