Supplementary Figure 5: Mg²⁺ concentration dependence of the J-K–HEAT-1 interaction.

(a) Results of ITC experiments in which the HEAT-1 domain was titrated to the J-K region at 2, 1, 0.5, and 0 mM of Mg²⁺. The interaction between the J-K region and the HEAT-1 domain requires divalent ions as seen by the lack of heat of interaction in the absence Mg²⁺ ions. (b) NMR spectral overlay. Left: Overlay of the ¹H-¹³C HMQC spectra of [¹³C,¹⁵N-Ade] J-K in the absence (black) and presence of 1 mM Mg²⁺ (red). Right: Overlay of the ¹H-¹H NOESY spectra of [u-²H, {H1′,H2′,H2,H8}-Ade] J-K in the absence (black) and presence of 1 mM Mg²⁺ (red). (c) SAXS profiles of the J-K region in the absence (black) and presence of excess (2 mM) Mg²⁺ (red). (d) Results of the ITC experiment in which Mg²⁺ was titrated to the J-K region.