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Related Concept Videos

Protein Denaturation01:28

Protein Denaturation

The function of proteins depends on their native three-dimensional structure, which is dictated by the amino acid sequence of the specific protein. Folding of the polypeptide chain takes place under specific conditions that energetically favor the folded conformation. In contrast, protein denaturation occurs spontaneously under unfavorable conditions that disrupt the integrity of the folded conformation. Thus, the chemical and physical environment of a protein, such as significant changes in pH...
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Point and Frameshift Mutations01:30

Point and Frameshift Mutations

Point mutations are genetic alterations involving the change of a single nucleotide base pair in DNA. Depending on how the alteration affects protein synthesis, they can lead to various consequences.Point mutations fall into the following types:Silent mutations occur when a nucleotide change does not alter the amino acid sequence due to the redundancy of the genetic code. For instance, changing ACC to ACA still encodes threonine, leaving the protein function unaffected. This occurs because...
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Environment-dependent long-range structural distortion in a temperature-sensitive point mutant.

Jannette Carey1, Brian Benoff, Balasubramanian Harish

  • 1Chemistry Department, Princeton University, Princeton, New Jersey 08544, USA. jcarey@princeton.edu

Protein Science : a Publication of the Protein Society
|November 8, 2011
PubMed
Summary
This summary is machine-generated.

The E. coli trp aporepressor undergoes significant structural changes near its DNA binding site and L-tryptophan pocket. These rearrangements, observed in crystal structures, explain its varied biochemical properties.

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Area of Science:

  • Structural Biology
  • Biochemistry
  • Molecular Biology

Background:

  • The E. coli trp aporepressor regulates tryptophan biosynthesis by binding to DNA.
  • Understanding its conformational flexibility is crucial for deciphering gene regulation mechanisms.

Purpose of the Study:

  • To elucidate the structural consequences of a specific point mutation (Leu75Phe) in the E. coli trp aporepressor.
  • To investigate the environment-dependent rearrangements within the aporepressor's DNA recognition and ligand-binding regions.

Main Methods:

  • X-ray crystallography was used to determine the crystal structure of the mutant dimeric E. coli trp aporepressor.
  • Comparison with an isomorphous wildtype control structure was performed.

Main Results:

  • A point mutation (Leu75Phe) induced extensive, environment-dependent rearrangements in one subunit, shifting helical regions and forming an extrahelical loop.
  • The second subunit maintained a wildtype-like conformation, indicating differential conformational states within the dimer.
  • The ensemble of distorted and wildtype-like conformations better explained previously observed NOE measurements and apoprotein properties.

Conclusions:

  • The study reveals significant structural plasticity in the trp aporepressor, influenced by mutations and potentially the cellular environment.
  • Steric constraints from beta-branched residues may play a key role in maintaining helical conformation in specific segments.
  • The findings provide insights into the dynamic nature of transcription regulation at a molecular level.