Structure of the bc₁ Complex from Seculamonas ecuadoriensis, a Jakobid Flagellate with an Ancestral Mitochondrial Genome

authored by

Stefanie Marx, Maja Baumgärtner, Sivakumar Kunnan, Hans Peter Braun, B. Franz Lang, Gertraud Burger

Abstract

In eubacteria, the respiratory bc₁ complex (complex III) consists of three or four different subunits, whereas that of mitochondria, which have descended from an α-proteobacterial endosymbiont, contains about seven additional subunits. To understand better how mitochondrial protein complexes evolved from their simpler bacterial predecessors, we purified complex III of Seculamonas ecuadoriensis, a member of the jakobid protists, which possess the most bacteria-like mitochondrial genomes known. The S. ecuadoriensis complex III has an apparent molecular mass of 460 kDa and exhibits antimycin-sensitive quinol:cytochrome c oxidoreductase activity. It is composed of at least eight subunits between 6 and 46 kDa in size, including two large "core" subunits and the three "respiratory" subunits. The molecular mass of the S. ecuadoriensis bC₁ complex is slightly lower than that reported for other eukaryotes, but about 2× as large as complex III in bacteria. This indicates that the departure from the small bacteria-like complex III took place at an early stage in mitochondrial evolution, prior to the divergence of jakobids. We posit that the recruitment of additional subunits in mitochondrial respiratory complexes is a consequence of the migration of originally et α-proteobacterial genes to the nucleus.

Organisation(s)

Institute of Plant Genetics

External Organisation(s)

University of Montreal
Helmholtz Centre for Infection Research (HZI)

Type

Article

Journal

Molecular biology and evolution

Volume

20

Pages

145-153

No. of pages

9

ISSN

0737-4038

Publication date

01.01.2003

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Ecology, Evolution, Behavior and Systematics, Molecular Biology, Genetics

Electronic version(s)

https://doi.org/10.1093/molbev/msg016 (Access: Open)