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Journal of Bacteriology, July 1999, p. 4076-4080, Vol. 181, No. 13
Institut für Mikrobiologie und Genetik,
Georg-August-Universität, 37077 Göttingen, Germany
Received 1 February 1999/Accepted 27 April 1999
The membrane-bound H2:heterodisulfide oxidoreductase
system of the methanogenic archaeon Methanosarcina mazei
Gö1 catalyzed the H2-dependent reduction of
2-hydroxyphenazine and the dihydro-2-hydroxyphenazine-dependent reduction of the heterodisulfide of HS-CoM and HS-CoB (CoM-S-S-CoB). Washed inverted vesicles of this organism were found to couple both
processes with the transfer of protons across the cytoplasmic membrane.
The maximal H+/2e
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Energy Conservation by the
H2:Heterodisulfide Oxidoreductase from Methanosarcina
mazei Gö1: Identification of Two Proton-Translocating
Segments
ratio was 0.9 for each
reaction. The electrochemical proton gradient (
µH+) thereby generated was shown to drive ATP synthesis from ADP plus Pi, exhibiting stoichiometries of
0.25 ATP synthesized per two electrons transported for both partial reactions. ATP synthesis and the generation of
µH+ were abolished by the uncoupler
3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF
6847). The ATP synthase inhibitor
N,N'-dicyclohexylcarbodiimide did not affect
H+ translocation but led to an almost complete inhibition
of ATP synthesis and decreased the electron transport rates. The latter effect was relieved by the addition of SF 6847. Thus, the
energy-conserving systems showed a stringent coupling which resembles
the phenomenon of respiratory control. The results indicate that two
different proton-translocating segments are present in the
H2:heterodisulfide oxidoreductase system; the first
involves the 2-hydroxyphenazine-dependent hydrogenase, and the second
involves the heterodisulfide reductase.
*
Corresponding author. Mailing address: Institut
für Mikrobiologie und Genetik, Universität Göttingen,
Grisebachstr. 8, 37077 Göttingen, Germany. Phone: (49) 551 393812. Fax: (49) 551 393793. E-mail: udeppen{at}gwdg.de.
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