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A1Ao-ATP synthase of Methanobrevibacter ruminantium couples sodium ions for ATP synthesis under physiological conditions.

ABSTRACT: An unresolved question in the bioenergetics of methanogenic archaea is how the generation of proton-motive and sodium-motive forces during methane production is used to synthesize ATP by the membrane-bound A(1)A(o)-ATP synthase, with both proton- and sodium-coupled enzymes being reported in methanogens. To address this question, we investigated the biochemical characteristics of the A(1)A(o)-ATP synthase (MbbrA(1)A(o)) of Methanobrevibacter ruminantium M1, a predominant methanogen in the rumen. Growth of M. ruminantium M1 was inhibited by protonophores and sodium ionophores, demonstrating that both ion gradients were essential for growth. To study the role of these ions in ATP synthesis, the ahaHIKECFABD operon encoding the MbbrA(1)A(o) was expressed in Escherichia coli strain DK8 (?atp) and purified yielding a 9-subunit protein with an SDS-stable c oligomer. Analysis of the c subunit amino acid sequence revealed that it consisted of four transmembrane helices, and each hairpin displayed a complete Na(+)-binding signature made up of identical amino acid residues. The purified MbbrA(1)A(o) was stimulated by sodium ions, and Na(+) provided pH-dependent protection against inhibition by dicyclohexylcarbodiimide but not tributyltin chloride. ATP synthesis in inverted membrane vesicles lacking sodium ions was driven by a membrane potential that was sensitive to cyanide m-chlorophenylhydrazone but not to monensin. ATP synthesis could not be driven by a chemical gradient of sodium ions unless a membrane potential was imposed. ATP synthesis under these conditions was sensitive to monensin but not cyanide m-chlorophenylhydrazone. These data suggest that the M. ruminantium M1 A(1)A(o)-ATP synthase exhibits all the properties of a sodium-coupled enzyme, but it is also able to use protons to drive ATP synthesis under conditions that favor proton coupling, such as low pH and low levels of sodium ions.

SUBMITTER: McMillan DG

PROVIDER: S-EPMC3220524 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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A1Ao-ATP synthase of Methanobrevibacter ruminantium couples sodium ions for ATP synthesis under physiological conditions.

McMillan Duncan G G DG Ferguson Scott A SA Dey Debjit D Schröder Katja K Aung Htin Lin HL Carbone Vincenzo V Attwood Graeme T GT Ronimus Ron S RS Meier Thomas T Janssen Peter H PH Cook Gregory M GM

The Journal of biological chemistry 20110927 46

An unresolved question in the bioenergetics of methanogenic archaea is how the generation of proton-motive and sodium-motive forces during methane production is used to synthesize ATP by the membrane-bound A(1)A(o)-ATP synthase, with both proton- and sodium-coupled enzymes being reported in methanogens. To address this question, we investigated the biochemical characteristics of the A(1)A(o)-ATP synthase (MbbrA(1)A(o)) of Methanobrevibacter ruminantium M1, a predominant methanogen in the rumen. ...[more]

PMID: 21953465

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Project description:Medium chain fatty acids (MCFA) have been shown to inhibit methanogenesis, disrupt the cell envelope, and decrease survival of Methanobrevibacter ruminantium M1 in a dose-, time-, and protonation level dependent way. However, the exact mechanisms behind these observations are still unknown. Although the biochemistry of the metabolic processes of M. ruminantium has been well studied and its genome sequence is now available, little is known about the overall transcriptome regulation of M. ruminantium in response to inhibitors like MCFA. In the present study, we used RNA Sequencing to evaluate the effects of lauric acid (C12) on M. ruminantium. Pure M. ruminantium cell cultures in the mid-exponential growth phase were exposed to C12 in concentrations of 0.4 mg/mL, dissolved in DMSO for 1 h, and the transcriptomic changes compared to DMSO-only treated control samples (final DMSO concentration 0.2 %), were investigated. Gene expression changes upon exposure to C12 were not dramatic in magnitude (log2 fold change mostly below +/- 3) and in gene number (214 genes). However, the observed expression changes affected mostly genes which encoded cell-surface associated proteins (adhesion-like proteins, membrane-associated transporters and hydrogenases), or proteins, which were involved in detoxification or DNA repair processes. The transcriptional response of M. ruminantium M1 to C12 did not specifically inhibit methanogenesis. Instead, the data indicated a non-specific antimicrobial action by lauric acid, which involves destruction of the cell membrane and interferences with cellular energetics in M. ruminantium. To date, there has been no systematic characterization of a ruminal methanogen transcriptome by deep sequencing. Our results give first hints on the molecular inhibitory mechanism of C12 on M. ruminantium. RNA profiles of M. ruminantium treated in vitro (lauric acid disolved in DMSO), non-treated=controls (DMSO supplementation) and non-treated=blanks (no supplementation) were generated by deep sequencing, in triplicates, by using Illumina HiSeq2500

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A1Ao-ATP synthase of Methanobrevibacter ruminantium couples sodium ions for ATP synthesis under physiological conditions.

Publications

A1Ao-ATP synthase of Methanobrevibacter ruminantium couples sodium ions for ATP synthesis under physiological conditions.

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