A non-invasive NMR method based on histidine imidazoles to analyze the pH-modulation of protein-nucleic acid interfaces

Abstract

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A useful ²J(NH) coupling-based NMR spectroscopic approach is proposed to unveil, at the molecular level, the contribution of the imidazole groups of histidines from RNA/DNA-binding proteins on the modulation of binding to nucleic acids by pH. Such protonation/deprotonation events have been monitored on the single His96 located at the second RNA/DNA recognition motif (RRM2) of T-cell intracellular antigen-1 (TIA-1) protein. The pK<inf>a</inf> values of the His96 ionizable groups were substantially higher in the complexes with short U-rich RNA and T-rich DNA oligonucleotides than those of the isolated TIA-1 RRM2. Herein, the methodology applied to determine changes in pK<inf>a</inf> of histidine side chains upon DNA/RNA binding, gives valuable information to understand the pH effect on multidomain DNA/RNA-binding proteins that shuttle among different cellular compartments.