A novel pathway of cytochrome c biogenesis is involved in the assembly of the cytochrome b6f complex in arabidopsis chloroplasts.
We recently characterized a novel heme biogenesis pathway required for heme c(i)' covalent binding to cytochrome b6 in Chlamydomonas named system IV or CCB (cofactor assembly, complex C (b6f), subunit B (PetB)). To find out whether this CCB pathway also operates in higher plants and extend the knowledge of the c-type cytochrome biogenesis, we studied Arabidopsis insertion mutants in the orthologs of the CCB genes. The ccb1, ccb2, and ccb4 mutants show a phenotype characterized by a deficiency in the accumulation of the subunits of the cytochrome b6f complex and lack covalent heme binding to cytochrome b6. These mutants were functionally complemented with the corresponding wild type cDNAs. Using fluorescent protein reporters, we demonstrated that the CCB1, CCB2, CCB3, and CCB4 proteins are targeted to the chloroplast compartment of Arabidopsis. We have extended our study to the YGGT family, to which CCB3 belongs, by studying insertion mutants of two additional members of this family for which no mutants were previously characterized, and we showed that they are not functionally involved in the CCB system. Thus, we demonstrate the ubiquity of the CCB proteins in chloroplast heme c(i)' binding.
Lezhneva
Lina
L
CNRS, UMR 7141, Laboratoire de Physiologie Membranaire et Moléculaire du Chloroplaste, Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France.
Kuras
Richard
R
Ephritikhine
Geneviève
G
de Vitry
Catherine
C
D020418:Algal Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002696:Chlamydomonas / Q000201:enzymology / Q000235:genetics; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics; D045346:Cytochrome b6f Complex / Q000235:genetics / Q000378:metabolism*; D045304:Cytochromes c / Q000235:genetics* / Q000378:metabolism; D006418:Heme / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism
D020418:Algal Proteins; D029681:Arabidopsis Proteins; C104657:PetB protein, plant; D010940:Plant Proteins; D015800:Protozoan Proteins; D006418:Heme; D045304:Cytochromes c; D045346:Cytochrome b6f Complex