Table 1.

Occupancy of Aurora A conformations under different conditions.

Ligand(s)	Ligand concentration [μm]	K m, K i, or IC50 [μm]	Inactive T‐loop [%][a]	Active T‐loop [%][a]	K eq [b]	ΔG inactive–active at 25 °C [kcal mol−1][c]
Apo	–	–	23	77	0.3	0.7
MLN8054	10	0.0003[d]	43	57	0.7	0.2
CD532	10	0.048[e]	64	36	1.8	−0.4
TPX2	5	0.01[f]	14	86	0.2	1.1
TPX2/MLN8054	5/10	0.01[f]/0.0003[d]	15	85	0.2	1.0
AMPPNP	1000	ND	22	78	0.3	0.7
ATP	1000	36[g]	32	68	0.5	0.5
Kemptide	3000	330[g]	21	79	0.3	0.8
AMPPNP/Kemptide	1000/3000	ND/330[h]	30	70	0.4	0.5
TPX2/AMPPNP/Kemptide	5/1000/3000	0.01[f]/ND/330[h]	12	88	0.1	1.2

[a] The error of the loop occupancy is propagated from the fitting error of the histograms and is ≤2. [b] K _eq=[inactive T‐loop]/[active T‐loop]. The error on K _eq is propagated from the fitting error of the histograms and is <0.1. [c] ΔG _{inactive–active}=−RT ln(K _eq). The error on ΔG _{inactive–active} is propagated from fitting errors of the histograms and is ≤0.1 kcal mol⁻¹. [d] K _i from Ref. 5b. [e] IC₅₀ from Ref. 5d. [f] EC₅₀ from Ref. 4b. [g] K _m from Ref. 4b. [h] K _m measured in this study (Figure S3) with an error of ±70 μm. ND=not determined.