tailieunhanh - Báo cáo khoa học: Involvement of Ech hydrogenase in energy conservation of Methanosarcina mazei

Methanosarcina mazeibelongs to the group of aceticlastic methanogens and converts acetate into the potent greenhouse gases CO2 and CH4. The aceticlastic respiratory chain involved in methane formation comprises the three transmembrane proteins Ech hydrogenase, F420 nonreducing hydroge-nase and heterodisulfide reductase. | Involvement of Ech hydrogenase in energy conservation of Methanosarcina mazei Cornelia Welte Christian Kratzer and Uwe Deppenmeier Institute of Microbiology and Biotechnology University of Bonn Germany Keywords archaea electron transport electron transport phosphorylation methane methanogenesis proton motive force proton pump Correspondence U. Deppenmeier Institut fur Mikrobiologie und Biotechnologie University of Bonn Meckenheimer Allee 168 53115 Bonn Germany Fax 49 228 737576 Tel 49 228 735590 E-mail udeppen@ Received 27 April 2010 revised 16 June 2010 accepted 17 June 2010 doi Methanosarcina mazei belongs to the group of aceticlastic methanogens and converts acetate into the potent greenhouse gases CO2 and CH4. The aceticlastic respiratory chain involved in methane formation comprises the three transmembrane proteins Ech hydrogenase F420 nonreducing hydrogenase and heterodisulfide reductase. It has been shown that the latter two contribute to the proton motive force. The data presented here clearly demonstrate that Ech hydrogenase is also involved in energy conservation. ATP synthesis was observed in a cytoplasm-free vesicular system of Ms. mazei that was dependent on the oxidation of reduced ferredoxin and the formation of molecular hydrogen as catalysed by Ech hydrogenase . Such an ATP formation was not observed in a Dech mutant strain. The protonophore 3 5-di-tert-butyl-4-hydroxybenzylidene-malononitrile SF6847 led to complete inhibition of ATP formation in the Ms. mazei wild-type without inhibiting hydrogen production by Ech hydrogenase whereas the sodium ion ionophore ETH157 did not affect ATP formation in this system. Thus we conclude that Ech hydrogenase acts as primary proton pump in a ferredoxin-dependent electron transport system. Introduction Biological methanogenesis from acetate is one of the most important processes for the maintenance of the carbon cycle on Earth. The products of methanogenesis from .