FIGURE 5.

The interaction of peptide (P₁₀) with OASS. A, the dissociation constant. Peptide binding to OASS was monitored via fluorescence changes at 510 nm (λ_ex 414 nm). Titrations were carried out in Hepes/K⁺ (50 mm, pH 7.0) at 25 ± 2 °C. The concentration of OASS_dimer was 0.50 μm. B, rate constants. Binding was initiated by rapidly mixing (1:1) OASS_dimer (6.25 nm, final) with P₁₀ (at the concentrations indicated). Solutions were buffered using Hepes/K⁺ (50 mm, pH 7.0) and equilibrated at 25 ± 2 °C prior to mixing. Reaction progress was monitored using fluorescence (λ_ex 414 nm, λ_em > 455 nm). k_obs values were determined in triplicate: each value was obtained by fitting the average of ten progress curves to a single-exponential decay. k_on (7.7 × 10⁶ m⁻¹ s⁻¹) and k_off (3.6 s⁻¹) were obtained by fitting the k_obs versus [P₁₀] data using the equation: k_obs = k_on · [pep] + k_off.