Plant Molecular Biology

, 68:505 | Cite as

Import of preproteins into the chloroplast inner envelope membrane

  • Ewa Firlej-Kwoka
  • Penelope Strittmatter
  • Jürgen Soll
  • Bettina BölterEmail author


The chloroplast inner envelope membrane contains many integral proteins which differ in the number of α-helices that anchor the protein into the bilayer. For most of these proteins it is not known which pathway they engage to reach their final localisation within the membrane. In yeast mitochondria, two distinct sorting/insertion pathways have been described for integral inner membrane proteins, involving the Tim22 and Tim23 translocases. These routes involve on the one hand a conservative sorting, on the other hand a stop-transfer pathway. In this study we performed a systematic characterisation of the import behaviour of seven inner envelope proteins representing different numbers of predicted α-helices. We investigated their energy dependence, import rate, involvement of components of the chloroplast general import pathway and distribution between soluble and membrane fractions. Our results show the existence of at least two different families of inner envelope proteins that can be classified due to the occurrence of an intermediate processing form. Each of the proteins we investigated seems to use a stop-transfer pathway for insertion into the inner envelope.


Chloroplast Protein import Inner envelope membrane Stop-transfer 





Essential for respiration and vegetative growth 1


Hypothetical protein


Inner envelope protein


Leader peptidase


Mitochondrial IMS import and assembly protein of 40 kDa


Mature form of the oxygen evolving complex protein of 33 kDa


Permease in chloroplasts 1


Plastidic signal peptidase type I protease 1


Precursor of the oxygen evolving complex protein of 33 kDa


Phosphoenolpyruvate translocator


Precursor of the small subunit of the Ribulosebisphosphatecarboxylase/oxygenase


Sorting and assembly machinery


Stromal processing peptidase


Translocon at the inner envelope of chloroplasts


Translocation intermediate 4


Translocase of the inner mitochondrial membrane


Translation product


Translocon at the outer envelope of chloroplasts



We acknowledge funding by the DFG (P. S., J. S. and B. B.) and Bayhost (E. F.-K.) and we thank Prof. Bob Buchanan for critical reading of the manuscript.


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Ewa Firlej-Kwoka
    • 1
    • 2
  • Penelope Strittmatter
    • 1
    • 2
  • Jürgen Soll
    • 1
    • 2
  • Bettina Bölter
    • 1
    • 2
    Email author
  1. 1.Department Biology I, Plant BiochemistryLudwig-Maximilians-Universität MünchenPlanegg-MartinsriedGermany
  2. 2.Munich Center for Integrated Protein Science CiPSMLudwig-Maximilians-Universität MünchenMunichGermany

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