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PMID:20628047

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Citation

Gabilly, ST, Dreyfuss, BW, Karamoko, M, Corvest, V, Kropat, J, Page, MD, Merchant, SS and Hamel, PP (2010) CCS5, a thioredoxin-like protein involved in the assembly of plastid c-type cytochromes. J. Biol. Chem. 285:29738-49

Abstract

The c-type cytochromes are metalloproteins with a heme molecule covalently linked to the sulfhydryls of a CXXCH heme-binding site. In plastids, at least six assembly factors are required for heme attachment to the apo-forms of cytochrome f and cytochrome c(6) in the thylakoid lumen. CCS5, controlling plastid cytochrome c assembly, was identified through insertional mutagenesis in the unicellular green alga Chlamydomonas reinhardtii. The complementing gene encodes a protein with similarity to Arabidopsis thaliana HCF164, which is a thylakoid membrane-anchored protein with a lumen-facing thioredoxin-like domain. HCF164 is required for cytochrome b(6)f biogenesis, but its activity and site of action in the assembly process has so far remained undeciphered. We show that CCS5 is a component of a trans-thylakoid redox pathway and operates by reducing the CXXCH heme-binding site of apocytochrome c prior to the heme ligation reaction. The proposal is based on the following findings: 1) the ccs5 mutant is rescued by exogenous thiols; 2) CCS5 interacts with apocytochrome f and c(6) in a yeast two-hybrid assay; and 3) recombinant CCS5 is able to reduce a disulfide in the CXXCH heme-binding site of apocytochrome f.

Links

PubMed PMC2943297 Online version:10.1074/jbc.M109.099069

Keywords

Animals; Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Binding Sites; Chlamydomonas reinhardtii/genetics; Chlamydomonas reinhardtii/metabolism; Cytochromes c/genetics; Cytochromes c/metabolism; Cytochromes c6/genetics; Cytochromes c6/metabolism; Cytochromes f/genetics; Cytochromes f/metabolism; Heme/genetics; Heme/metabolism; Mutation; Oxidation-Reduction; Protozoan Proteins/genetics; Protozoan Proteins/metabolism; Thioredoxins/genetics; Thioredoxins/metabolism; Thylakoids/genetics; Thylakoids/metabolism

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

CHLRE:D3K371

GO:0015036: disulfide oxidoreductase activity

ECO:0000315:

F

Figure 6

complete

CHLRE:D3K371

GO:0015979: photosynthesis

ECO:0000315:

P

Figure 2a, The mutant phenotype is photosynthetic deficient.

complete

CHLRE:D3K371

GO:0017004: cytochrome complex assembly

ECO:0000315:

P

Figure 5a

complete


See also

References

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