Table 1.

Stability of active conformation in MEK1 variants reported through differences in computed free energies between states: active–inactive; active–stable; inactive–stable

In order of least active to most active systems (reorder this)	Δ Free energy (kcal/mol)			Conformation most stabilized KE salt bridge: DFG flip: A-loop (Inactive = 0, Active = 1, anything intermediate = 0.5)
	Active-inactive	Active-stable	Inactive-stable
WT	12.85	12.85	0	[0:0:0]
SSDD	7.91	10.58	2.67	[0:0.5:0]
DP MEK	4.94	8.15	3.21	[0:0:0.5]
F53S	1.65	11.93	10.28	[0.5:0.5:0.5]
	−10.28	0	10.28	(if the most stable zone is kinase active)
E203K	1.05	2.53	1.48	[0.5:0.5:1]
	−1.48	0	1.48	(if the most stable zone is kinase active)

The third column lists the status of the [KE salt bridge: DFG flip: A-loop], each showing either Inactive = 0, Active = 1, or intermediate = 0.5 characteristics.