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Tandem binding in crystals of a trp repressor/operator half-site complex
1Biology Department, Brookhaven National Laboratory, Upton, New York 11973.
Nature
|November 11, 1993
Summary
The trp repressor protein binds DNA in a tandem 2:1 complex, forming a structure crucial for gene regulation. This detailed structural analysis reveals conserved protein-DNA interactions and the role of specific protein regions in recognition.
Area of Science:
- Structural Biology
- Molecular Biology
- Genetics
Background:
- The trp repressor regulates gene expression by binding to specific DNA operator sequences.
- Previous structures revealed a 1:1 complex, but in vivo, tandem binding is observed.
Purpose of the Study:
- To determine the crystal structure of the trp repressor in a tandem 2:1 complex with its DNA operator.
- To elucidate the molecular basis of DNA recognition and protein-protein interactions in the tandem complex.
Main Methods:
- X-ray crystallography to determine the protein-DNA complex structure.
- Refinement of the crystal structure to 2.4 A resolution.
Main Results:
- The crystal structure of a 2:1 trp repressor-DNA complex was determined.
- The protein/DNA interface is highly conserved compared to the 1:1 complex.
- Water-mediated recognition and an end-on approach of helix E were observed.
- The tandem interaction, involving amino-terminal arms, explains operator mutational sensitivity.
Conclusions:
- The trp repressor utilizes a conserved interface for DNA binding, even in tandem complexes.
- Water molecules play a key role in sequence recognition.
- The amino-terminal arms are critical for the tandem protein-DNA interaction and gene regulation.