The assembly of cytochrome b6/f complexes: an approach using genetic transformation of the green alga Chlamydomonas reinhardtii.

Kuras, Richard; Wollman, Françis Andrè

doi:10.1002/j.1460-2075.1994.tb06350.x

Cited by 197 publications

(250 citation statements)

References 31 publications

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“…The defect in cytochrome b 6 f biogenesis in the absence of CCDA is most likely the result of compromised assembly of the complex, consistent with the observation that holocytochrome f is required for the assembly of the b 6 f complex in Chlamydomonas (53). A definite placement of CCDA in the plastid c-type cytochrome assembly pathway also relies on the examination of the assembly of cytochrome c X , the other c-type cytochrome occurring in the thylakoid lumen in Arabidopsis (54).…”

Section: Discussionsupporting

confidence: 84%

A Homolog of Prokaryotic Thiol Disulfide Transporter CcdA Is Required for the Assembly of the Cytochrome bf Complex in Arabidopsis Chloroplasts

Page¹,

Hamel²,

Gabilly³

et al. 2004

Journal of Biological Chemistry

101

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The c-type cytochromes are defined by the occurrence of heme covalently linked to the polypeptide via thioether bonds between heme and the cysteine sulfhydryls in the CXXCH motif of apocytochrome. Maintenance of apocytochrome sulfhydryls in a reduced state is a prerequisite for covalent ligation of heme to the CXXCH motif. In bacteria, a thiol disulfide transporter and a thioredoxin are two components in a thio-reduction pathway involved in c-type cytochrome assembly. We have identified in photosynthetic eukaryotes nucleus-encoded homologs of a prokaryotic thiol disulfide transporter, CcdA, which all display an N-terminal extension with respect to their bacterial counterparts. The extension of Arabidopsis CCDA functions as a targeting sequence, suggesting a plastid site of action for CCDA in eukaryotes. Using PhoA and LacZ as topological reporters, we established that Arabidopsis CCDA is a polytopic protein with within-membrane strictly conserved cysteine residues. Insertional mutants in the Arabidopsis CCDA gene were identified, and loss-of-function alleles were shown to impair photosynthesis because of a defect in cytochrome b 6 f accumulation, which we attribute to a block in the maturation of holocytochrome f, whose heme binding domain resides in the thylakoid lumen. We postulate that plastid cytochrome c maturation requires CCDA, thioredoxin HCF164, and other molecules in a membrane-associated trans-thylakoid thiol-reducing pathway.The c-type cytochromes are a virtually ubiquitous yet rather structurally diverse group of hemoproteins that reside on the so-called p-side 1 of the energy-transducing membrane systems where they function typically as electron carriers (1, 2). The c-type cytochromes are defined by the occurrence of heme covalently attached to the polypeptide via two thioether linkages between the vinyl groups of heme and the cysteine sulfhydryls in the apocytochrome (1, 3). A CXXCH 2 sequence in the apocytochrome provides the thiols for formation of the thioether bonds, and the imidazole of the histidine residue serves as one of the axial ligands of the heme. Remarkably, three distinct assembly pathways, referred to as systems I, II, and III, have emerged through genetic analysis of c-type cytochrome maturation in bacteria, chloroplasts, and mitochondria (for review, see Refs. 1 and 4 -7), an unexpected finding for what appears on the surface to be a rather simple chemical reaction (i.e. the addition of apocytochrome cysteine thiols to the vinyls of heme). Each system can be distinguished on the basis of a sequence relationship of specific assembly factors. Yet, there is an underlying assumption that the three systems are united by common biochemical requirements for holocytochrome c biogenesis (for review, see Refs. 2, 4, and 8). For instance, the need for reducing conditions appears to be inherent to the chemistry of thioether bond formation (4). Both substrates, apocytochrome c sulfhydryls and heme, need to be maintained reduced prior to the ligation of heme as indicated from in vitro and in o...

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Section: Discussionsupporting

confidence: 84%

A Homolog of Prokaryotic Thiol Disulfide Transporter CcdA Is Required for the Assembly of the Cytochrome bf Complex in Arabidopsis Chloroplasts

Page¹,

Hamel²,

Gabilly³

et al. 2004

Journal of Biological Chemistry

101

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“…f showed no significant changes, because preexisting cyt. b 6 f complexes are stable over this time period (18). In contrast, the petA transcript decreased in parallel with the loss in MCA1-HA, whereas 16S rRNA remained unaffected.…”

mentioning

confidence: 80%

“…Unassembled cyt. f down-regulates its translation (18,27), most probably by trapping TCA1 by way of its C-terminal regulatory region (34). In tca1 transformants displaying high expression of cyt.…”

Section: Major Traits For the Nuclear Regulation Of Cytochrome F Exprmentioning

confidence: 99%

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Evidence for regulatory function of nucleus-encoded factors on mRNA stabilization and translation in the chloroplast

Raynaud

Loiselay

Wostrikoff

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

104

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A salient feature of organelle gene expression is the requirement for nucleus-encoded factors that act posttranscriptionally in a gene-specific manner. A central issue is to understand whether these factors are merely constitutive or have a regulatory function. In the unicellular alga Chlamydomonas reinhardtii, expression of the chloroplast petA gene-encoding cytochrome f, a major subunit of the cytochrome b 6f complex, depends on two specific nucleusencoded factors: MCA1, required for stable accumulation of the petA transcript, and TCA1, required for its translation. We cloned the TCA1 gene, encoding a pioneer protein, and transformed appropriate mutant strains with tagged versions of MCA1 and TCA1. In transformed strains expressing decreasing amounts of MCA1 or TCA1, the concentration of these factors proved limiting for petA mRNA accumulation and cytochrome f translation, respectively. This observation suggests that in exponentially growing cells, the abundance of MCA1 sets the pool of petA transcripts, some of which are TCA1-selected for an assembly-dependent translation of cytochrome f. We show that MCA1 is a short-lived protein. Its abundance varies rapidly with physiological conditions that deeply affect expression of the petA gene in vivo, for instance in aging cultures or upon changes in nitrogen availability. We observed similar but more limited changes in the abundance of TCA1. We conclude that in conditions where de novo biogenesis of cytochrome b 6f complexes is not required, a rapid drop in MCA1 exhausts the pool of petA transcripts, and the progressive loss of TCA1 further prevents translation of cytochrome f.

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“…Numerous studies have highlighted diverse mechanisms that coordinate expression of nuclear and plastidial genes involved in an identical process (Barkan and Goldschmidt-Clermont, 2000;Choquet and Wollman, 2002;Gray et al, 2003). Moreover, unassembled subunits of the same complex can be degraded as a consequence of their biochemical instability in the absence of their partners (Kuras and Wollman, 1994). Even though such a phenomenon has only been described for the subunits of multimeric enzymes or photosynthesis complexes until now, it could also exist for components of the plastid division machinery.…”

Section: Discussionmentioning

confidence: 99%

An Arabidopsis Homolog of the Bacterial Cell Division Inhibitor SulA Is Involved in Plastid Division[W]

et al. 2004

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Plastids have evolved from an endosymbiosis between a cyanobacterial symbiont and a eukaryotic host cell. Their division is mediated both by proteins of the host cell and conserved bacterial division proteins. Here, we identified a new component of the plastid division machinery, Arabidopsis thaliana SulA. Disruption of its cyanobacterial homolog (SSulA) in Synechocystis and overexpression of an AtSulA-green fluorescent protein fusion in Arabidopsis demonstrate that these genes are involved in cell and plastid division, respectively. Overexpression of AtSulA inhibits plastid division in planta but rescues plastid division defects caused by overexpression of AtFtsZ1-1 and AtFtsZ2-1, demonstrating that its role in plastid division may involve an interaction with AtFtsZ1-1 and AtFtsZ2-1.

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The assembly of cytochrome b6/f complexes: an approach using genetic transformation of the green alga Chlamydomonas reinhardtii.

Cited by 197 publications

References 31 publications

A Homolog of Prokaryotic Thiol Disulfide Transporter CcdA Is Required for the Assembly of the Cytochrome bf Complex in Arabidopsis Chloroplasts

A Homolog of Prokaryotic Thiol Disulfide Transporter CcdA Is Required for the Assembly of the Cytochrome bf Complex in Arabidopsis Chloroplasts

Evidence for regulatory function of nucleus-encoded factors on mRNA stabilization and translation in the chloroplast

An Arabidopsis Homolog of the Bacterial Cell Division Inhibitor SulA Is Involved in Plastid Division[W]

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