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Dimer-to-tetramer assembly of Lac repressor involves a leucine heptad repeat
S Alberti1, S Oehler, B von Wilcken-Bergmann
1Institut für Genetik der Universität zu Köln, FRG.
The New Biologist
|January 1, 1991
Summary
The C-terminus of the Lac repressor protein facilitates the formation of tetramers from dimers. This region, similar to leucine zippers, relies on hydrophobic residues for protein interactions.
Area of Science:
- Molecular biology
- Protein structure and function
- Genetics
Background:
- The C-terminus of the Lac repressor is crucial for forming repressor tetramers from active dimers.
- The Lac repressor's C-terminal domain (amino acids 331-360) can convert Gal repressor dimers into tetramers when grafted.
Purpose of the Study:
- To investigate the role of specific amino acids in the Lac repressor's C-terminus in mediating protein-protein interactions.
- To determine the structural basis for tetramer formation in Lac repressor.
Main Methods:
- Systematic amino acid replacements within residues 342-356 of the Lac repressor.
- Analysis of protein-protein interactions and tetramer formation.
- Comparison with leucine zipper motifs in eukaryotic transcription factors.
Main Results:
- The 4-3 hydrophobic repeat (four leucines and one valine) within amino acids 342-356 is essential for repressor dimer-dimer interaction.
- Hydrophobic residues within this repeat are critical for constitutive coiled-coil formation.
- The tetramerization site of Lac repressor shares similarities with eukaryotic leucine zipper motifs.
Conclusions:
- The C-terminal region of Lac repressor, particularly its hydrophobic repeat, is a key determinant of tetramer formation.
- This tetramerization mechanism resembles the leucine zipper motif found in eukaryotic transcription factors, suggesting conserved protein interaction strategies.