[Spatial structure of the cro-repressor in a solution. I. Identification of interaction in a hydrophobic cluster using the nuclear Overhauser effect].

The structure of a bacteriophage lambda cro repressor hydrophobic globule was studied by the technique of 1H NMR spectroscopy at 500 MHz. The analysis of NOE difference spectra and building of the molecular models for the most probable fragments of the secondary structure allowed us to assign many signals in the protein spectrum and to identify the intramolecular interactions which stabilized the hydrophobic globule and the tertiary structure of the molecule. The results suggest that the structure of the cro repressor hydrophobic globule in solution coincides with the crystal one, although there are some differences in the mutual arrangement of the alpha 1 helix and the three-fold beta-sheet. Resonance assignment has made it possible to study conformational changes and specific interactions of the cro repressor by using suitable reporter groups.