Cpn20: Siamese twins of the chaperonin world

Celeste Weiss, Anat Bonshtien, Odelia Farchi-Pisanty, Anna Vitlin, Abdussalam Azem*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


The chloroplast cpn20 protein is a functional homolog of the cpn10 co-chaperonin, but its gene consists of two cpn10-like units joined head-to-tail by a short chain of amino acids. This double protein is unique to plastids and was shown to exist in plants as well plastid-containing parasites. In vitro assays showed that this cpn20 co-chaperonin is a functional homolog of cpn10. In terms of structure, existing data indicate that the oligomer is tetrameric, yet it interacts with a heptameric cpn60 partner. Thus, the functional oligomeric structure remains a mystery. In this review, we summarize what is known about this distinctive chaperonin and use a bioinformatics approach to examine the expression of cpn20 in Arabidopsis thaliana relative to other chaperonin genes in this species. In addition, we examine the primary structure of the two homologous domains for similarities and differences, in comparison with cpn10 from other species. Lastly, we hypothesize as to the oligomeric structure and raison d'être of this unusual co-chaperonin homolog.

Original languageEnglish
Pages (from-to)227-238
Number of pages12
JournalPlant Molecular Biology
Issue number3
StatePublished - Feb 2009


FundersFunder number
United States - Israel Binational Agricultural Research and Development FundIS-3906-06
Israel Science Foundation


    • Chaperonin
    • Cpn10
    • Cpn20
    • Cpn21
    • Protein folding


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