FIGURE 6.

Monitoring changes in the ¹H,¹³C HMQC spectra of Sos^Cat upon the addition of Ras. The Met methyl resonances of Sos^Cat (A–E) (red) and Sos^CatW729E (F) (red) were monitored upon the addition of Ras at a Ras:Sos stoichiometry of 0.5:1 (blue), 1:1 (green), 1.5:1 (orange), 2:1 (cyan), 3:1 (purple), and 4:1 (black) in the HMQC spectra. The titrated Ras form is H-Ras^NF (A), H-Ras·GDP (B), H-Ras·GTPγS (C), K-Ras·GTPγS (D), K-RasG12V·GTPγS (E), and H-Ras·GTPγS (F). Chemical shift perturbations and signal broadening are indicated as black boxes and dashed boxes, respectively. Characteristic states occurring for the M824^(c) signal upon addition of H-Ras·GTPγS are marked in C as I, II, and III.