FIG. 6.

Activation of Krp1 in Xenopus egg extract. Krp1 mRNA was translated in Xenopus egg extract for 1 h in the presence of [³H]leucine. Cycloheximide was added (final concentration, 2 mM) to inhibit any further translation, and incubation was continued for various times (as indicated) before samples were analyzed by SDS-PAGE. The amount of Krp1 in each sample was determined by using a PhosphorImager (Molecular Dynamics) with ImageQuant software, and equivalent amounts of protein were assayed for the ability to cleave the fluorogenic substrate Boc-Arg-Thr-Lys-Arg-MCA. Activity was determined under initial rate conditions and is expressed relative to the maximum activity observed in the experiment. The positions of molecular weight markers (in thousands) are shown to the left of the gel.