Chloroplast β chaperonins from A. thaliana function with endogenous cpn10 homologs in vitro

Anna Vitlin, Celeste Weiss, Keren Demishtein-Zohary, Aviram Rasouly, Doron Levin, Odelia Pisanty-Farchi, Adina Breiman, Abdussalam Azem

Research output: Contribution to journalArticlepeer-review

Abstract

The involvement of type I chaperonins in bacterial and organellar protein folding has been well-documented. In E. coli and mitochondria, these ubiquitous and highly conserved proteins form chaperonin oligomers of identical 60 kDa subunits (cpn60), while in chloroplasts, two distinct cpn60 α and β subunit types co-exist together. The primary sequence of α and β subunits is ~50% identical, similar to their respective homologies to the bacterial GroEL. Moreover, the A. thaliana genome contains two α and four β genes. The functional significance of this variability in plant chaperonin proteins has not yet been elucidated. In order to gain insight into the functional variety of the chloroplast chaperonin family members, we reconstituted β homo-oligomers from A. thaliana following their expression in bacteria and subjected them to a structure-function analysis. Our results show for the first time, that A. thaliana β homo-oligomers can function in vitro with authentic chloroplast co-chaperonins (ch-cpn10 and ch-cpn20). We also show that oligomers made up of different β subunit types have unique properties and different preferences for co-chaperonin partners. We propose that chloroplasts may contain active β homo-oligomers in addition to hetero-oligomers, possibly reflecting a variety of cellular roles.

Original languageEnglish
Pages (from-to)105-115
Number of pages11
JournalPlant Molecular Biology
Volume77
Issue number1
DOIs
StatePublished - Sep 2011

Keywords

  • A. thaliana
  • Chaperonin
  • Chloroplast
  • Cpn10
  • Cpn60
  • Protein folding

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