FIGURE 9.

Lipin 1β catalytic efficiency but not PA affinity is modified by c-Fos. PAP I activity was measured as a function of the indicated molar concentrations of PA (a) and as a function of the indicated surface concentrations of PA (b) with or without the addition of recombinant c-Fos. For the experiment shown in a, the molar ratio of PA to Triton X-100 was maintained at 9.1 mol %. For the experiment shown in b, the molar concentration of PA was maintained at 1 mm, and the Triton X-100 concentration was varied to obtain the indicated surface concentrations. In both types of experiments, c-Fos mol % was kept constant at 9.09 × 10⁻⁶ mol %, meaning that the ratio between c-Fos to total lipid remains constant. The c-Fos mol % used was the same as in Fig. 2b at 100 nm c-Fos, where the highest activation was achieved. The data shown are means ± S.D. from triplicate enzyme determinations. The best fit curves were derived from the kinetic analysis of the data.