The complexity of chloroplast chaperonins

Gruber, Anna; Nisemblat, Shahar; Azem, Abdussalam; Weiss, Celeste

doi:10.1016/j.tplants.2013.08.001

Cited by 50 publications

(38 citation statements)

References 89 publications

(150 reference statements)

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“…As recently demonstrated by in vitro reconstitution 14 , folding of cyanobacterial RbcL requires the chaperonin GroEL and its cofactor GroES (Cpn60, Cpn10 and Cpn20 in chloroplasts 15 ). The spontaneous assembly of folded RbcL is inefficient and has been shown to be facilitated by a specific assembly chaperone, RbcX 14,16 .…”

mentioning

confidence: 84%

Structure and mechanism of the Rubisco-assembly chaperone Raf1

Hauser

Bhat

Miličić

et al. 2015

Nat Struct Mol Biol

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Biogenesis of the photosynthetic enzyme Rubisco, a complex of eight large (RbcL) and eight small (RbcS) subunits, requires assembly chaperones. Here we analyzed the role of Rubisco accumulation factor1 (Raf1), a dimer of ∼40-kDa subunits. We find that Raf1 from Synechococcus elongatus acts downstream of chaperonin-assisted RbcL folding by stabilizing RbcL antiparallel dimers for assembly into RbcL8 complexes with four Raf1 dimers bound. Raf1 displacement by RbcS results in holoenzyme formation. Crystal structures show that Raf1 from Arabidopsis thaliana consists of a β-sheet dimerization domain and a flexibly linked α-helical domain. Chemical cross-linking and EM reconstruction indicate that the β-domains bind along the equator of each RbcL2 unit, and the α-helical domains embrace the top and bottom edges of RbcL2. Raf1 fulfills a role similar to that of the assembly chaperone RbcX, thus suggesting that functionally redundant factors ensure efficient Rubisco biogenesis.

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mentioning

confidence: 84%

Structure and mechanism of the Rubisco-assembly chaperone Raf1

Hauser

Bhat

Miličić

et al. 2015

Nat Struct Mol Biol

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“…CPN20 is part of the family of Type I chaperonins that function in protein folding together with CPN60 proteins and CPN10 proteins (Koumoto et al, 1999;Sharkia et al, 2003;Vitlin Gruber et al, 2013). It remains to be determined if and how CPN20 has a functional relationship to ClpT1 and ClpT2.…”

Section: Interactions Between Clpt and Cpn20mentioning

confidence: 99%

Structures, Functions, and Interactions of ClpT1 and ClpT2 in the Clp Protease System of Arabidopsis Chloroplasts

et al. 2015

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“…3) Both chaperonin and co-chaperonin subunits can assemble into a variety of functional homo- and hetero-oligomeric complexes. Cpn60αβ hetero-oligomer is the most abundant oligomeric form in vivo (reviewed in [10]), although the Cpn60β subunits were shown to be functional as homo-oligomers in vitro [11]. In terms of co-chaperonins, Cpn10 and Cpn20 can function in vitro as heptameric and tetrameric homo-oligomers, respectively [12]–[15].…”

Section: Introductionmentioning

confidence: 99%

The Cpn10(1) Co-Chaperonin of A. thaliana Functions Only as a Hetero-Oligomer with Cpn20

et al. 2014

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The A. thaliana genome encodes five co-chaperonin homologs, three of which are destined to the chloroplast. Two of the proteins, Cpn10(2) and Cpn20, form functional homo-oligomers in vitro. In the current work, we present data on the structure and function of the third A. thaliana co-chaperonin, which exhibits unique properties. We found that purified recombinant Cpn10(1) forms inactive dimers in solution, in contrast to the active heptamers that are formed by canonical Cpn10s. Additionally, our data demonstrate that Cpn10(1) is capable of assembling into active hetero-oligomers together with Cpn20. This finding was reinforced by the formation of active co-chaperonin species upon mixing an inactive Cpn20 mutant with the inactive Cpn10(1). The present study constitutes the first report of a higher plant Cpn10 subunit that is able to function only upon formation of hetero-oligomers with other co-chaperonins.

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The complexity of chloroplast chaperonins

Cited by 50 publications

References 89 publications

Structure and mechanism of the Rubisco-assembly chaperone Raf1

Structure and mechanism of the Rubisco-assembly chaperone Raf1

Structures, Functions, and Interactions of ClpT1 and ClpT2 in the Clp Protease System of Arabidopsis Chloroplasts

The Cpn10(1) Co-Chaperonin of A. thaliana Functions Only as a Hetero-Oligomer with Cpn20

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