ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P199. A Novel Respiratory Complex in Desulfovibrio vulgaris
Hildenborough
S. Venceslau, I. Cardoso Pereira
a Microbial Biochemistry, Instituto de Tecnologia Química e Tecnológica, U, Av. da República, EAN, 2780-157,
Oeiras, Portugal
e-mail: sofiav@itqb.unl.pt
Sulfate-reducing organisms are anaerobic prokaryotes found ubiquitously in nature. They use a respiratory
mechanism with sulfate as the terminal electron acceptor, but the intervenients in the respiratory chain have not
been fully elucidated. Here, we describe a novel multihemic cytochrome complex isolated from the membranes
of Desulfovibrio vulgaris Hildenborough, composed by four subunits (72, 48, 31 and 24 kDa). The 24 kDa
protein is a periplasmic penta or hexaheme c membrane anchored subunit, the 31 kDa protein is an FeS protein
that may also contain one heme c, and the 48 kDa subunit is an integral membrane protein. Although the
periplasmic 72 kDa subunit is annotated as a molybdopterin oxidoreductase subunit, no Mo was detected. This
complex is the first example described of the so-called MFIc complexes, proposed to be oxidoreductases of the
respiratory electron transfer chains. These complexes are related to the MFIcc class, which have already been
reported as an alternative complex III, when this one is absent: in the anoxigenic phototrophic bacterium
Chloroflexus aurentiacus, and in the aerobic non-phototrophic bacterium Rhodothermus marinus[1, 2]. The D.
vulgaris MFIc complex is present in large amounts suggesting an important role in the energy metabolism. This
is supported by expression studies, where the complex behaves similarly to other proteins directly involved in
the sulphate respiratory chain[3]. However, its electron donor and acceptor are still not known.
References:
[1] Yanyushin, M.F., et al., New class of bacterial membrane oxidoreductases. Biochemistry, 2005. 44(30):
p. 10037-45.
[2] Pereira, M.M., et al., The alternative complex III from Rhodothermus marinus - a prototype of a new family
of quinol:electron acceptor oxidoreductases. FEBS Lett, 2007. 581(25): p. 4831-5.
[3] Pereira, P.M., et al., Transcriptional response of Desulfovibrio vulgaris Hildenborough to oxidative stress
mimicking environmental conditions. Arch Microbiol, 2008. 189(5): p. 451-61.
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