On the oligomeric state of chloroplast chaperonin 10 and chaperonin 20

Rajach Sharkia, Anat L. Bonshtien, Itzhak Mizrahi, Celeste Weiss, Adina Niv, Ariel Lustig, Paul V. Viitanen, Abdussalam Azem

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Type I chaperonins are fundamental protein folding machineries that function in eubacteria, mitochondria and chloroplasts. Eubacteria and mitochondria contain chaperonin systems comprised of homo-oligomeric chaperonin 60 tetradecamers and co-chaperonin 10 heptamers. In contrast, the chloroplast chaperonins are heterooligomeric tetradecamers that are composed of two subunit types, α and β. Additionally, chloroplasts contain two structurally distinct co-chaperonins. One, ch-cpn10, is probably similar to the mitochondrial and bacterial co-chaperonins, and is composed of 10 kDa subunits. The other, termed ch-cpn20 is composed of two cpn10-like domains that are held together by a short linker. While the oligomeric structure of ch-cpn10 remains to be elucidated, it was previously suggested that ch-cpn20 forms tetramers in solution, and that this is the functional oligomer. In the present study, we investigated the properties of purified ch-cpn10 and ch-cpn20. Using bifunctional cross-linking reagents, gel filtration chromatography and analytical ultracentrifugation, we show that ch-cpn10 is a heptamer in solution. In contrast, ch-cpn20 forms multiple oligomers that are in dynamic equilibrium with each other and cover a broad spectrum of molecular weights in a concentration-dependent manner. However, upon association with GroEL, only one type of co-chaperonin-GroEL complex is formed.

Original languageEnglish
Pages (from-to)76-84
Number of pages9
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Issue number1-2
StatePublished - 23 Sep 2003
Externally publishedYes


  • Chaperonin
  • Chloroplast
  • Cpn10
  • Cpn20
  • Cpn60
  • GroES

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biophysics
  • Biochemistry
  • Molecular Biology


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