Journal Article

HCF208, a Homolog of <i>Chlamydomonas</i> CCB2, is Required for Accumulation of Native Cytochrome <i>b</i><sub>6</sub> in <i>Arabidopsis thaliana</i>

Dagmar Lyska, Susanne Paradies, Karin Meierhoff and Peter Westhoff

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 12, pages 1737-1746
Published in print December 2007 | ISSN: 0032-0781
Published online December 2007 | e-ISSN: 1471-9053 | DOI:
HCF208, a Homolog of Chlamydomonas CCB2, is Required for Accumulation of Native Cytochrome b6 in Arabidopsis thaliana

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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The cytochrome b6 subunit of the cytochrome b6f complex is a multiheme protein. Two b-type hemes are bound non-covalently to the protein, whereas the third heme (heme cn) is covalently attached via an atypical thioether bond. To understand the maturation of cytochrome b6 and to identify the assisting factors, we characterized the ethyl methanesulfonate-induced nuclear mutant hcf208. This Arabidopsis mutant shows a high chlorophyll fluorescence phenotype and does not accumulate the major cytochrome b6f complex subunits. Transcript levels and patterns of the four major polypeptides of the complex are equal to those of the wild type. The mutant cytochrome b6 polypeptide shows a faster migration behavior in SDS–PAGE compared with the wild type and it has no peroxidase activity. The HCF208 locus was mapped and the gene was cloned. Sequence analysis revealed that HCF208 is a homolog of the Chlamydomonas reinhardtii CCB2 protein, which is a factor mediating attachment of heme cn to the cytochrome b6 polypeptide as part of a novel heme biogenesis pathway, called system IV. Blue Native PAGE revealed residual amounts of the cytochrome b6f complex dimer in hcf208; however, this form is unable to participate in electron transport reactions.

Keywords: Arabidopsis; Chloroplast; Cytochrome b6f complex; Heme attachment; Heme cn

Journal Article.  5686 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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