AtCCMH, an essential component of the c-type cytochrome maturation pathway in Arabidopsis mitochondria, interacts with apocytochrome c

Etienne H. Meyer, Philippe Giegé, Eric Gelhaye, Naganand Rayapuram, Umesh Ahuja, Linda Thöny-Meyer, Jean Michel Grienenberger, Géraldine Bonnard*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

The maturation of c-type cytochromes requires the covalent ligation of the heme cofactor to reduced cysteines of the CXXCH motif of apocytochromes. In contrast to mitochondria of other eukaryotes, plant mitochondria follow a pathway close to that found in α- and γ-proteobacteria. We identified a nuclear-encoded protein, AtCCMH, the Arabidopsis thaliana ortholog of bacterial CcmH/CycL proteins. In bacteria, CcmH and the thioredoxin CcmG are components of a periplasmic thio-reduction pathway proposed to maintain the apocytochrome c cysteines in a reduced state. AtCCMH is located exclusively in mitochondria. AtCCMH is an integral protein of the inner membrane with the conserved RCXXC motif facing the intermembrane space. Reduction assays show that the cysteine thiols in the RCXXC motif of AtCCMM can form a disulfide bond that can be reduced by enzymatic thiol reductants. A reduced form of AtCCMH can reduce the intra-disulfide bridge of a model peptide of apocytochrome c. When expressed in Escherichia coli, AtCCMH coimmunoprecipitates with the bacterial CcmF, a proposed component of the heme lyase. Blue-native PAGE of mitochondrial membrane complexes reveals the colocalization of AtCCMM and AtCcmFN2 in a 500-kDa complex. Yeast two-hybrid assays show an interaction between the AtCCMH intermembrane space domain and A. thaliana apocytochrome c. A. thaliana ccmh/ ccmh knockout plants show lethality at the torpedo stage of embryogenesis. Our results show that AtCCMH is an essential mitochondrial protein with characteristics consistent with its proposed apocytochrome c-reducing and heme lyase function.

Original languageEnglish (US)
Pages (from-to)16113-16118
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number44
DOIs
StatePublished - Nov 1 2005

Keywords

  • Cytochrome c
  • Disulfide reductase
  • Embryo-lethal
  • Heme lyase
  • Plant mitochondria

ASJC Scopus subject areas

  • General

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