Conformational Studies of Two Non‐histone Chromosomal Proteins and Their Interactions with DNA

Abstract

The conformational properties of 2 [calf thymus] non-histone chromosomal proteins (high-mobility-group proteins 1 and 2) were studied by spectroscopic methods. The interaction of high-mobility-group protein 1 with DNA was also studied. Circular dichroism results indicate that in the presence of salt both proteins are 40-50% helical between pH 1-9. Above pH 9 denaturation takes place. In the absence of salt the proteins denature below pH 4. NMR spectra show the presence of ring-current shifted peaks and perturbed aromatic resonances, demonstrating that the helix formation is accompanied by specific tertiary folding. NMR spectra of complexes between high mobility group orotein 1 and DNA demonstrate that at low ionic strength a portion of the molecule rich in lysine and containing all the aromatic residues is bound to DNA, while a more acidic region of the chain remains free from the DNA.