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Plant Molecular Biology

, Volume 77, Issue 1–2, pp 105–115 | Cite as

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 AzemEmail author
Article

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.

Keywords

Chaperonin Chloroplast A. thaliana Cpn60 Cpn10 Protein folding 

Abbreviations

MDH

Malate dehydrogenase

TEV

Tobacco Etch virus

Mt

Mitochondrial

Ch

Chloroplast

cpn10

10 kDa co-chaperonin

cpn60

60 kDa chaperonin

β homo-oligomer

ch-cpn60 oligomer composed of identical β subunits

αβ hetero-oligomer

ch-cpn60 oligomer composed of a mixture of α and β subunits

CD

Circular dichroism

DTT

Dithiothreitol

Notes

Acknowledgments

This work was supported by the Binational Agricultural Research and Development Fund (BARD Project IS-3906-06). We would like to thank Avital Parnas for useful discussions and critical review of this manuscript.

Supplementary material

11103_2011_9797_MOESM1_ESM.ppt (152 kb)
Supplementary material 1 (PPT 152 kb)
11103_2011_9797_MOESM2_ESM.ppt (42 kb)
Supplementary material 2 (PPT 42 kb)

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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Anna Vitlin
    • 1
  • Celeste Weiss
    • 1
  • Keren Demishtein-Zohary
    • 1
  • Aviram Rasouly
    • 1
  • Doron Levin
    • 1
  • Odelia Pisanty-Farchi
    • 2
  • Adina Breiman
    • 2
  • Abdussalam Azem
    • 1
    Email author
  1. 1.Department of Biochemistry and Molecular BiologyTel Aviv UniversityTel AvivIsrael
  2. 2.Department of Molecular Biology and Ecology of PlantsTel Aviv UniversityTel AvivIsrael

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