Methanococcus voltae

Niess UM, A Klein (2004) Dimethylselenide demethylation is an adaptaive response to selenium deprivation in the urchaeon Methanococcus voltae. J Bacterial 186 3640-3648. 

The importance of H2 metabolism to some organisms is highlighted by their possession of more than one hydrogenase system. Four hydrogenase systems are known in Escherichia coli and Methanococcus voltae, three in Desufovibrio vulgaris and... 

Berghofer, Y., Agha-Amiri, K. and Klein, A. (1994) Selenium is involved in the negative regulation of the expression of selenium-free [NiFe] hydrogenases in Methanococcus voltae. Mol. Gen. Genet., 242, 369-73. 

Halboth, S. (1991) Molekulargenetische Untersuchung der Hydrogenasen aus Methanococcus voltae. Ph.D., University of Marburg. 

Muth, E., Morschel, E. and Klein, A. (1987) Purification and characterization of an 8-hydroxy-5-deazaflavin- reducing hydrogenase from the archaebacterium Methanococcus voltae. Eur. J. Biochem., 169, 571-7. 

Sorgenfrei, O., Klein, A. and Albracht, S. P. J. (1993b) Influence of illumination on the electronic interaction between O2 and nickel in active F420-non-reducing hydrogenase from Methanococcus voltae. FEES Lett., 332, 291-7. 

Sorgenfrei, O., Muller, S., Pfeiffer, M., Sniezko, I. and Klein, A. (1997a) The [NiFe] hydrogenases of Methanococcus voltae. Genes, enzymes, and regulation. Arch. Microbiol., 167, 189-95. 

The sodium gradient in the methanogen Methanococcus voltae is exploited in the transport of isoleucine as a positively charged complex,74 where concentration gradients over 100 can be achieved. It is noteworthy that the methanogens represent one of the few cases where a growth requirement for Na+ can be shown.75,76... 

NiFeSe Methanococcus voltae, deazaflavin-reducing Soluble H2 consumption 48 + 33 + 80 Ni/Fe + n[4Fe-4S] F-420... 

P-type ATPase. Methanococcus voltae, a marine organism growing on H2/CO2, contains high activities of a membrane-bound ATPase, which was sensitive towards vanadate rather than to DCCD [147], suggesting the presence of a P-type ATPase (see ref [141]). Accordingly the purified enzyme, composed of one 74 kD subunit, could be phosphorylated in a vanadate-sensitive fashion [148], a characteristic property for P-type ATPases, which involve a phosphoprotein as intermediate in the catalytic cycle. 

H -translocating ATP synthase is most probably the same for all methanogens (for a controversial discussion of energy coupling in Methanococcus voltae see ref. [15]). 

The finding that in Methanococcus voltae protonophores did not affect ATP... 

The possibility that primary Na extrusion was driven by a Na -translocating ATPase was excluded The protonophore tetrachlorosalicylanilide was found to uncouple formaldehyde oxidation from ATP synthesis without affecting Na extrusion. Thus, ATP cannot be the driving force for Na extrusion in Methanosarcina barken. This situation may be different in Methanococcus voltae which appears to contain a Na -translocating ATPase (see above). 

Methanococcus voltae contains a membrane-bound vanadate-sensitive ATPase [48] that is inhibited by diethylstilbestrol, an inhibitor of eukaryotic P-type ATPases. The purified enzyme is composed of a single subunit (Mr 74 000), forms a covalent acyl-phosphate enzyme intermediate, and is not inhibited by nitrate or bafilomycin [49]. No such ATPase activity has been reported in other archaea. The presence of a second ATPase in M. voltae has been inferred since membranes react with antiserum prepared against the 3 subunit from the V-type ATPase of S. acidocaldarius [50]. Two peptides are detected whose Mr values (51 000 and 65 000) correspond to the masses for the two laigest subunits of the S. acidocaldarius ATPase [51]. There is evidence that ATP synthesis in the M. voltae enzyme is due to the operation of a sodium-translocating ATPase [50]. The relationship of the putative V-like ATPase to the sodium-translocating ATPase has not been established. 

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