Figure 6. 2D-HMQC NMR confirms R-state selection by ERK inhibitors.

2D(¹H,¹³C)-HMQC NMR spectra were collected on 2P-ERK2 at 25°C and 5°C. Effects on [methyl ¹H,¹³C] peaks of residues (A) I72, (B) L220 and (C) L242 are shown for the representative set of inhibitors in Fig. 4. Inhibitors #5, #6, #8 and #16 (shown in blue) shifted the R⇌L equilibrium to 100% R at all temperatures, confirming R-state selection as suggested by their HDX behaviors in Figs. 4 and 5. Inhibitors #4 and #15 (in grey) retained R:L populations comparable to those with GDC0994. Inhibitor #1 (in cyan) showed partial selection for the R state but retained conformational exchange, as evidenced by an L state population present at 5°C.