The Tmc complex from Desulfovibrio vulgaris Hildenborough is involved in transmembrane electron transfer from periplasmic hydrogen oxidation

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Abstract

Three membrane-bound redox complexes have been reported in Desulfovibrio spp., whose genes are not found in the genomes of other sulfate reducers such as Desulfotalea psycrophila and Archaeoglobus fulgidus. These complexes contain a periplasmic cytochrome c subunit of the cytochrome c3 family, and their presence in these organisms probably correlates with the presence of a pool of periplasmic cytochromes c3, also absent in the two other sulfate reducers. In this work we report the isolation and characterization of the first of such complexes, Tmc from D. vulgaris Hildenborough, which is associated with the tetraheme type II cytochrome c3. The isolated Tmc complex contains four subunits, including the TpIIc3 (TmcA), an integral membrane cytochrome b (TmcC), and two cytoplasmically predicted proteins, an iron-sulfur protein (TmcB) and a tryptophan-rich protein (TmcD). Spectroscopic studies indicate the presence of eight hemes c and two hemes b in the complex pointing to an α2βγδ composition (TmcA2BCD). EPR analysis reveals the presence of a [4Fe4S] 3+ center and up to three other iron-sulfur centers in the cytoplasmic subunit. Nearly full reduction of the redox centers in the Tmc complex could be obtained upon incubation with hydrogenase/TpIc3, supporting the role of this complex in transmembrane transfer of electrons resulting from periplasmic oxidation of hydrogen.

Original languageEnglish
Pages (from-to)10359-10367
Number of pages9
JournalBiochemistry
Volume45
Issue number34
DOIs
Publication statusPublished - 29 Aug 2006

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