Chloroplast Import of Four Carotenoid Biosynthetic Enzymes In Vitro Reveals Differential Fates Prior to Membrane Binding and Oligomeric Assembly

摘要: The precursor proteins of the carotenogenic enzymes geranylgeranyl diphosphate synthase, phytoene desaturase and lycopene cyclase were imported into isolated pea chloroplasts. Geranylgeranyl synthase remained soluble in stroma a free form associated to thylakoid membranes upon import, both as expected. Surprisingly, cyclase, which strongly depend on membrane association for enzymatic activity, also chloroplast stroma. forms these were, however, still competent membrane-association, e.g. with protein-free liposomal membranes. Indeed occurred ATP- cold-sensitive high-molecular-mass complexes. Gel-filtration experiments blue native-PAGE plus autoradiography western blot analysis indicated participation 60-kDa chaperonin (Cpn60) complexes enzymes. Finally, it was inferred that membrane-bound regulatory factor plays decisive role membrane-binding.