Fig. 2.

PDE4B_cryst is dimeric, free of aggregates and fully active when reduced. (A) Superimposed UV absorption elution profiles of cross-linked and reduced PDE4B_cryst and unmutated PDE4B1 (122–736). The major peak elutes at a position corresponding to a PDE4 dimer. Michaelis–Menten kinetics plots for PDE4B_cryst (B) reduced (specific activity 5.0 ± 0.2 µmol⋅min⁻¹·mg⁻¹, K_m 4.3 ± 0.5 µM) and (C) directly after purification, without addition of reducing agent (specific activity 0.078 ± 0.002 µmol⋅min⁻¹·mg⁻¹, K_m 8.4 ± 0.8 µM). Data shown are mean ± SEM from three independent experiments.