Table 2.
Case 1: SOS functions as both a RacGEF and an adaptora
| Reaction | kon (1/s) | koff (1/s) | kcat (1/s) |
|---|---|---|---|
| Gads binding to and unbinding from LAT without cooperativity | 0.1 | 5 | |
| Grb2-SOS binding to and unbinding from LAT | 0.12 | 0.8 | |
| PLCγ-RasGRP binding to and unbinding from LAT | 0.16 | 0.5 | |
| Gads unbinding from LAT bound with SOS and RasGRP | 0.01 | ||
| SOS activating Rac | 0.008 | ||
| Gads activating Rac without cooperativity | 0.005 | ||
| Gads activating Rac with cooperativity | 0.1 | ||
| Rac self-decaying to inactive form | 80 | ||
| Rac activating p38 | 1 | ||
| p38 self-decaying to inactive form | 35 |
a
When both Grb2-SOS and PLCγ-RasGRP bind to LAT, the LAT signalosome complex is more stable and more effective in activating Rac. Grb2-SOS, when bound to LAT, activates Rac directly.