Figure 6.

Conformational exchange in GDP‐loaded K‐Ras. (A) Correlation between ¹⁵ N backbone chemical shift differences deduced from relaxation dispersion measurements (CPMG) on G12C K‐Ras ⋅ Mg²⁺ ⋅ GDP (|Δδ _EG|) and those detected between the Mg²⁺‐bound and Mg²⁺‐free form (|Δδ _Mg|) of the complex. (B) Residues exhibiting a linear correlation between |Δδ _EG| and |Δδ _Mg| are indicated in green in a ball‐and‐stick representation on the ribbon diagram of G12C K‐Ras ⋅ Mg²⁺ ⋅ GDP. (C) Plot of the fit of the ¹⁵ N‐CEST experiment for a representative residue at the beginning of the switch‐II region (β3) in wt K‐Ras ⋅ Mg²⁺ ⋅ GDP. Numerical parameters of the fit are shown in Table 2. (D) Correlation between ¹⁵ N backbone chemical shift differences deduced from CEST experiments on wt (star), G12C (circle), G12D (triangle), and G12V (square) K‐Ras ⋅ Mg²⁺ ⋅ GDP (Δδ _EG ^CEST) and those detected between the corresponding Mg²⁺‐bound and a Mg²⁺‐free forms (Δδ _Mg). Fitted and estimated (based on the difference between the two minima of the CEST‐curve) values of Δδ _EG ^CEST are depicted in darker and lighter color, respectively.