Figure 3.

Chemical shift mapping of Mg²⁺ binding to the SL1m internal loop. (A) Overlay of 2D ¹H–¹³C and ¹H–¹⁵N HSQC spectra of SL1m recorded in the absence (in black) and presence (in red) of 5 mM Mg²⁺. (B) Residues undergoing the largest Mg²⁺-induced chemical shift perturbations (top 20% for a given type of resonance) and that yield the tightest binding (K_d < 2.0 mM) are highlighted on the SL1m secondary structure in red and using a black box, respectively. (C) Representative titration curves as a function of total Mg²⁺ concentration with apparent K_d values shown at the end of each curve.