N^ω-arginine dimethylation modulates the interaction between a gly/arg-rich peptide from human nucleolin and nucleic acids

We studied the interaction between a synthetic peptide (sequence Ac-GXGGFGGXGGFXGGXGGNH₂, where X = arginine, N^ω,N^ω-dimethylarginine, DMA, or lysine) corresponding to residues 676-692 of human nucleolin and several DNA and RNA substrates using double filter binding, melting curve analysis and circular dichroism spectroscopy. We found that despite the reduced capability of DMA in forming hydrogen bonds, N^ω,N^ω-dimethylation does not affect the strength of the binding to nucleic acids nor does it have any effect on stabilization of a double-stranded DNA substrate. However, circular dichroism studies show that unmethylated peptide can perturb the helical structure, especially in RNA, to a much larger extent than the DMA peptide.