Isolation and characterization of methanophenazine and function of phenazines in membrane-bound electron transport of Methanosarcina mazei Gö1.
A hydrophobic, redox-active component with a molecular mass of 538 Da was isolated from lyophilized membranes of Methanosarcina mazei Gö1 by extraction with isooctane. After purification on a high-performance liquid chromatography column, the chemical structure was analyzed by mass spectroscopy and nuclear magnetic resonance studies. The component was called methanophenazine and represents a 2-hydroxyphenazine derivative which is connected via an ether bridge to a polyisoprenoid side chain. Since methanophenazine was almost insoluble in aqueous buffers, water-soluble phenazine derivatives were tested for their ability to interact with membrane-bound enzymes involved in electron transport and energy conservation. The purified F42OH2 dehydrogenase from M. mazei Gö1 showed highest activity with 2-hydroxyphenazine and 2-bromophenazine as electron acceptors when F420H2 was added. Phenazine-1-carboxylic acid and phenazine proved to be less effective. The Km values for 2-hydroxyphenazine and phenazine were 35 and 250 microM, respectively. 2-Hydroxyphenazine was also reduced by molecular hydrogen catalyzed by an F420-nonreactive hydrogenase which is present in washed membrane preparations. Furthermore, the membrane-bound heterodisulfide reductase was able to use reduced 2-hydroxyphenazine as an electron donor for the reduction of CoB-S-S-CoM. Considering all these results, it is reasonable to assume that methanophenazine plays an important role in vivo in membrane-bound electron transport of M. mazei Gö1.
Abken
H J
HJ
Institut für Mikrobiologie und Genetik, Georg-August-Universität, Göttingen, Germany.
Tietze
M
M
Brodersen
J
J
Bäumer
S
S
Beifuss
U
U
Deppenmeier
U
U
D002462:Cell Membrane / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004579:Electron Transport; D007700:Kinetics; D013058:Mass Spectrometry; D017020:Methanosarcina / Q000378:metabolism*; D008956:Models, Chemical; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010088:Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D010619:Phenazines / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity
D010619:Phenazines; C111939:methanophenazine; C072742:F420H2 dehydrogenase; D010088:Oxidoreductases