Chloroplast import of four carotenoid biosynthetic enzymes in vitro reveals differential fates prior to membrane binding and oligomeric assembly

Michael Bonk, Benedikt Hoffmann, Johannes Von Lintig, Michael Schledz, Salim Al-Babili, Elias Hobeika, Hans Kleinig, Peter Beyer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

72 Scopus citations

Abstract

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

Original languageEnglish (US)
Pages (from-to)942-950
Number of pages9
JournalEuropean Journal of Biochemistry
Volume247
Issue number3
DOIs
StatePublished - Jan 1 1997

Keywords

  • Carotenoid
  • Chaperone]
  • Chloroplast import
  • Daffodil
  • Membrane binding

ASJC Scopus subject areas

  • Biochemistry

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