Nucleic acids-protein interactions. Conformational changes induced by the binding of aromatic amines to polyadenylic acid

Interaction of aromatic residues of proteins with nucleic acids. Circular dichroism studies of the binding of oligopeptides to poly(adenylic acid)

“…As the concentration of peptide is increased, the relative change of the CD amplitude seems to tend toward a limit, but this limit is not reached in the concentration range allowed by the absorption of the peptide. As reported elsewhere for aromatic amines (Durand et al" 1975) the size of the ring is an important factor in determining the magnitude of the observed decrease. 5: pH dependence of </ , the relative decrease of the CD signal, of poIy(A) at 262.5 nm alone (3.9 X 10-4 m) ( ) and in the presence of Lys-Trp-Lys (4.25 X -4 ) (O).…”

“…One can conclude that the changes observed in the CD spectrum correspond to a conformational change induced in poly(A) by peptide binding. In a previous paper (Durand et al, 1975), we have attributed this conformational change to the unstacking of poly(A) bases induced by base stacking with the aromatic ring of the amines. Such an unstacking is probably induced by the binding of the aromatic peptides as well, but there is a second contribution to the conformational change which is due to electrostatic binding of the lysyl residues as shown in the case of Lys-Ala-Lys which gives only this second type of interaction.…”

“…Circular Dichroism of the Peptides. The investigated peptides have optical activity which may interfere with the CD of poly(A) in contrast to aromatic amines whose binding to poly(A) has been described elsewhere (Durand et al, 1975). The CD spectra of the peptides Lys-X-Lys are shown in Figure 1.…”

Interaction of aromatic residues of proteins with nucleic acids. Binding of oligopeptides to copolynucleotides of adenine and cytosine

“…The CD data are plotted in units of M_1 cm-1. The analysis of CD data was done as previously described (Durand et al, 1975(Durand et al, , 1976). The decrease of the CD signal of the polynucleotide upon addition of peptide is measured at various figure 1: CD spectra of the various poly(A,C) in a pH 7 buffer containing 1 mM NaCl, 1 mM sodium cacodylate, 0.2 mM EDTA.…”

“…The decrease of the CD signal of the polynucleotide upon addition of peptide is measured at various figure 1: CD spectra of the various poly(A,C) in a pH 7 buffer containing 1 mM NaCl, 1 mM sodium cacodylate, 0.2 mM EDTA. Tem- (Durand et al, 1975(Durand et al, , 1976), the values of r calculated by this method correspond to the sum of all complexes whatever their respective effects on the CD spectrum of the polymer, as far as the distribution of ligands between complex I and complex II is independent of [P]0.…”