Stimulation of the methyltetrahydromethanopterin: coenzyme M methyltransferase reaction in cell-free extracts of Methanobacterium thermoautotrophicum by the heterodisulfide of coenzyme M and 7-mercaptoheptanoylthreonine phosphate

The conversion of formaldehyde to methylcoenzyme M in cell-free extracts of Methanobacterium thermoautotrophicum was stimulated up to 10-fold by catalytic amounts of the heterodisulfide (CoM-S-S-HTP) of coenzyme M and 7-mercaptoheptanoylthreonine phosphate. The stimulation required the additional presence of ATP, also in catalytic concentrations. ATP and CoM-S-S-HTP were mutually stimulatory on the methylcoenzyme M formation and it was concluded that the compounds were both involved in the reductive activation of the methyltetrahydromethanopterin: coenzyme M methyltransferase. Micromolar concentrations of benzyl viologen or cyanocobalamin inhibited the formaldehyde conversion; these compounds, however, strongly stimulated the reduction of CoM-S-S-HTP. The results described here closely resemble observations made on the activation and reduction of CO₂ to formylmethanofuran indicating that this step and the reductive activation of the methyltransferase are controlled by some common mechanism.Abbreviations HS-CoM Coenzyme M, 2-mercaptoethanesulfonate - CH₃S-CoM methylcoenzyme M, 2-(methylthio)ethanesulfonate - H₄MPT 5,6,7,8-tetrahydromethanopterin - MFR methanofuran - HS-HTP 7-mercaptoheptanoylthreonine phosphate - CoM-S-S-HTP the heterodisulfide of HS-CoM and HS-HTP - BES 2-bromoethanesulfonate - TES N-tris(hydroxymethyl)methyl-2-aminoethanesulfonate - CN-Cbl cyanocobalamin - HO-Cbl hydroxycobalamin - HBI 5-hydroxybenzimidazole - DMBI 5,6-dimethylbenzimidazole     

Glyceraldehyde-3-Phosphate Dehydrogenases from Archaea: Objects for Studying Protein Thermoadaptation

Functional and structural properties of the glyceraldehyde-3-phosphate dehydrogenases from the mesophilic archaeum Methanobacterium bryantii and from the hyperthermophilic archaea Methan-othermus fervidus, Pyrococcus woesei and Thermoproteus tenax were compared to characterize the thermophilic phenotype. Site dierected mutagenesis with the M. fervidus enzyme were performed to analyse the structural background of the thermoadaptive features of the archaeal glyceraldehyde-3-phosphate dehydrogenase.     

Conservation of primary structure in prokaryotic hydrogenases

Abstract All prokaryotic (NiFe)-hydrogenases so far studied at the primary sequence level appear to have evolved from a common ancestral sequence. Highly conserved cysteinyl and histidinyl residues indicate regions likely to be essential for enzyme activity, ligand and co-factor binding. There is a very highly conserved sequence over 100 basepairs (bp) in length within the intergenic region upstream of the methyl-viologen hydrogenase encoding genes in several different strains of Methanobacterium thermoautotrophicum , indicating that a sequence of this length is needed to direct and regulate the expression of these genes.     

ATP synthesis driven by a potassium diffusion potential in Methanobacterium thermoautotrophicum is stimulated by sodium

Abstract ATP synthesis driven by a potassium diffusion potential was studied in cell suspensions of Methanobacterium thermoautotrophicum (Marburg). This transient increase in the intracellular ATP content was stimulated five-fold by the addition of sodium ions, from about 2 nmol ATP/min × mg cells (dry weight) at 0.07 mM Na⁺ to about 10 nmol ATP/min × mg cells at 25 mM Na⁺.     

Isolation of lipid activated pseudomurein precursors from Methanobacterium thermoautotrophicum

From cell extracts of the pseudomurein possessing methanogen Methanobacterium thermoautotrophicum two putative pseudomurein precursors were isolated and characterized: (1) an undecaprenyl pyrophosphate activated disaccharide pentapeptide composed of N-acetylglucosamine, N-acetyltalosaminuronic acid, alanine, glutamic acid and lysine in a molar ratio of 1:1:2:2:1 and (2) the corresponding undecaprenyl pyrophosphate activated tetrapeptide lacking one alanine residue. The isolation of these precursors show that the biosynthesis of the eubacterial murein and the methano-bacterial pseudomurein differs not only in the cytoplasmic step, as recently described, but also in the lipid stage.Abbreviations GlcNitol glucosaminitol - NAcTalNUA N-acetyltalosaminuronic acid - Udp undecaprenol - TLC thin layer chromatography