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J Cell Biol. 2014 May 26;205(4):511-24. doi: 10.1083/jcb.201401009. Epub 2014 May 19.

Assembly factors monitor sequential hemylation of cytochrome b to regulate mitochondrial translation.

Author information

1
Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden.
2
Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824.
3
Centre de Génétique Moléculaire du Centre National de la Recherche Scientifique (CNRS), 91198 Gif-sur-Yvette, France.
4
Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden martin.ott@dbb.su.se.

Abstract

Mitochondrial respiratory chain complexes convert chemical energy into a membrane potential by connecting electron transport with charge separation. Electron transport relies on redox cofactors that occupy strategic positions in the complexes. How these redox cofactors are assembled into the complexes is not known. Cytochrome b, a central catalytic subunit of complex III, contains two heme bs. Here, we unravel the sequence of events in the mitochondrial inner membrane by which cytochrome b is hemylated. Heme incorporation occurs in a strict sequential process that involves interactions of the newly synthesized cytochrome b with assembly factors and structural complex III subunits. These interactions are functionally connected to cofactor acquisition that triggers the progression of cytochrome b through successive assembly intermediates. Failure to hemylate cytochrome b sequesters the Cbp3-Cbp6 complex in early assembly intermediates, thereby causing a reduction in cytochrome b synthesis via a feedback loop that senses hemylation of cytochrome b.

PMID:
24841564
PMCID:
PMC4033779
DOI:
10.1083/jcb.201401009
[Indexed for MEDLINE]
Free PMC Article

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