Figure 2.

Posttranslational uptake of in vitro synthesized precursor proteins. ³⁵S-labeled precursor of protoporphyrinogen IX oxidases I (PPX I) and II (PPX II) were synthesized by in vitro transcription/translation (TLS) and offered to intact pea chloroplasts (Left) or mitochondria (Right). (Left) Following the import reaction, plastids were either analyzed directly (PL) or after treatment with proteases (PL_P). Plastids were reisolated and fractionated into stroma (S) and membrane (M). (Right) Aliquots of the translation products (TLS) and of mitochondria after the import assay were incubated with (+) and without (−) proteinase K (PK) and applied to polyacrylamide gels. In both experiments, coproporphyrinogen oxidase (CPO) as a plastidal marker and a nuclear-encoded mitochondrial subunit of NADH:ubiquinone oxidoreductase (76 kDa) was included as a reference.