Figure 6.

Binding of hexyl isonicotinate to P450 2E1. P450 2E1 (2 μm) was mixed with hexyl isonicotinate concentrations of 1.0 (red), 2.0 (green), 5 (dark blue), 10 (light blue), and 20 (gold) μm. A, single exponential fits to traces of binding versus time. Linear regression analysis yielded k_on = 0.98 × 10⁶ m⁻¹ s⁻¹ and k_off = 1.3 s⁻¹ (results not shown). B, biexponential fit of data of A. C, fast (red points) and slow (green points) rates of binding as a function of substrate concentration. D, fits of binding data with a 2-state model (solid lines) for varying concentrations of hexyl isonicotinate, with k_on = 1.5 × 10⁶ m⁻¹ s⁻¹ and k_off = 1.2 s⁻¹. E, fits of data with an induced-fit model, with k₁ = 1.9 × 10⁶ m⁻¹ s⁻¹, k₋₁ = 5.5 s⁻¹, k₂ = 15 s⁻¹, and k₋₂ = 2.8 s⁻¹ (ϵ_430–410 19.5 mm⁻¹ cm⁻¹). F, fits of data with a conformational-selection model, with k₁ = 18 s⁻¹, and k₋₁ = 110 s⁻¹, k₂ = 10 × 10⁶ m⁻¹ s⁻¹, and k₋₂ 0.41 s⁻¹ (ϵ_430–410 15.5 mm⁻¹ cm⁻¹).