FIG. 4.

Prosequence cleavage between the primary and internal sites. Krp1 (shown as Krp1[KR82][KR102] to emphasize the sequences at the primary and internal sites) and Krp1[IA82][KA102] mRNAs were translated in Xenopus egg extract for 1 h in the presence of [³H]leucine, and the products were separated by SDS-PAGE before being transferred to a PVDF membrane. The positions of proteins were identified by autoradiography, and the sections of the membrane corresponding to the proteins were excised and subjected to cycle sequencing. The amount of [³H]leucine in each cycle was determined by scintillation counting and compared to the protein sequences. The cleavage sites are indicated by black arrows, and shaded arrows indicate the positions of mutated sites in Krp1[IA82][KA102].