title: Chloroplast β chaperonins from A. thaliana function with endogenous cpn10 homologs in vitro.
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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Tel Aviv University, 69978 Tel Aviv, Israel.
authors.forename: Anna
authors.initials: A
authors.lastname: Vitlin
authors.forename: Celeste
authors.initials: C
authors.lastname: Weiss
authors.forename: Keren
authors.initials: K
authors.lastname: Demishtein-Zohary
authors.forename: Aviram
authors.initials: A
authors.lastname: Rasouly
authors.forename: Doron
authors.initials: D
authors.lastname: Levin
authors.forename: Odelia
authors.initials: O
authors.lastname: Pisanty-Farchi
authors.forename: Adina
authors.initials: A
authors.lastname: Breiman
authors.forename: Abdussalam
authors.initials: A
authors.lastname: Azem
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D018745:Genome, Plant; D056384:Group I Chaperonins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D020033:Protein Isoforms; D021122:Protein Subunits; D056384:Group I Chaperonins