A protein structure from nuclear magnetic resonance data. lac repressor headpiece

Area of Science:

• Structural Biology
• Biophysics
• Molecular Modeling

Background:

• Determining the three-dimensional structure of biomolecules is crucial for understanding their function.
• Nuclear magnetic resonance (NMR) spectroscopy provides valuable distance information for structural elucidation.
• The N-terminal DNA-binding domain (headpiece) of the lac repressor is essential for gene regulation but lacks a crystal structure.

Purpose of the Study:

• To develop and apply a computational procedure for determining biomolecular 3D structures from NMR data.
• To elucidate the three-dimensional structure of the lac repressor headpiece.
• To compare the structural features of the lac repressor headpiece with homologous proteins.

Main Methods:

• A hybrid approach combining de novo model building with a restrained molecular dynamics algorithm.
• Incorporation of distance restraints derived from nuclear Overhauser effects (NOEs) as pseudo potentials.
• Application of the method to the N-terminal DNA-binding domain (residues 1-51) of the Escherichia coli lac repressor.

Main Results:

• The procedure successfully determined the three-dimensional structure of the lac repressor headpiece.
• The determined structure reveals the relative orientation of the three major helices within the headpiece.
• Structural comparison showed similarity between the lac repressor headpiece helices and those of the bacteriophage lambda cI repressor.

Conclusions:

• The described procedure is effective for determining the 3D structure of biomolecules using NMR data, especially when crystal structures are unavailable.
• The structural insights gained are valuable for understanding the DNA-binding mechanism of the lac repressor.
• The study highlights conserved structural motifs in DNA-binding proteins across different organisms.