Influence of amino acid and peptide counterions on the conformation of DNA.
We describe fibre diffraction studies on the interaction of DNA with different amino acids and peptides. The B form of DNA, with ten base-pairs per turn, is always found at high levels of humidity. We suggest that this pitch is observed because the DNA molecules are maintained in a straight position. In solution, the DNA molecules are bent and may have a larger pitch. The A form of DNA is never found upon dehydration. Instead, the B form may be either stabilized by the counterions or altered so that the number of base-pairs per helical turn decreases upon dehydration. Alteration is favoured either by small counterions that have a single charge or by large basic polypeptides and proteins. Stabilization is favoured by small counterions that have several charged groups. A third type of behaviour is found with some amino acids that contain hydrophobic groups, which destabilize the secondary structure of DNA, probably due to a modification of its intramolecular interactions. We have not detected any specific effect of amino acid side-chains, although the amino acid sequence has a clear influence on the interaction. We think that these observations are of interest in the pursuit of more detailed crystallographic studies on protein-DNA interactions.
J L
JL
Campos
J
J
Portugal
J A
JA
Subirana
R
R
Mayer
D000596:Amino Acids; D000818:Animals; D002417:Cattle; D004247:DNA; D009690:Nucleic Acid Conformation; D010455:Peptides; D011487:Protein Conformation; D014961:X-Ray Diffraction
D000596:Amino Acids; D010455:Peptides; D004247:DNA