Figure 4. Perturbations of TIAR2^L chemical shifts upon RNA binding. (A) An overlay of the assigned (¹⁵N,¹H)-HSQC spectra of TIAR2^L alone and in complex with different concentrations of 6-nt AU-rich RNA (5′-UUAUUU-3′). The molar ratio of TIAR2^L to RNA is 1:0 (black), 1:0.4 (red), 1:0.8 (pink) and 1:1.2 (blue). (B) Chemical shift perturbation values for each residue were calculated at the TIAR2^L to RNA 1:1.2 ratio as Δδ = {[0.154 (δ¹⁵N)²+ 0.25 (δ¹³Cα)²+ 0.25 (δ¹³Cβ)²+ (δ¹H)²]/4}^1/2 and plotted against the amino acid sequence of TIAR2^L. The 20 residues showing the largest perturbations upon RNA-binding are colored (red > 0.20 ppm; orange > 0.14 ppm; yellow > 0.08 ppm). (C) Cartoon representation of the TIAR RRM2 structure (PDB ID: 2DH7) with residues affected by RNA-binding colored as in (B) with residues that showed lesser chemical shift perturbations upon RNA binding colored gray.