Publications

• The MtsA subunit of the methylthiol:coenzyme M methyltransferase of Methanosarcina barkeri catalyses both half-reactions of corrinoid-dependent dimethylsulfide: coenzyme M methyl transfer.

  Tallant T.C., Paul L., Krzycki J.A.

  Methanogenesis from dimethylsulfide requires the intermediate methylation of coenzyme M. This reaction is catalyzed by a methylthiol:coenzyme M methyltransferase composed of two polypeptides, MtsA (a methylcobalamin:coenzyme M methyltransferase) and MtsB (homologous to a class of corrinoid protein ... >> More

  Methanogenesis from dimethylsulfide requires the intermediate methylation of coenzyme M. This reaction is catalyzed by a methylthiol:coenzyme M methyltransferase composed of two polypeptides, MtsA (a methylcobalamin:coenzyme M methyltransferase) and MtsB (homologous to a class of corrinoid proteins involved in methanogenesis). Recombinant MtsA was purified and found to be a homodimer that bound one zinc atom per polypeptide, but no corrinoid cofactor. MtsA is an active methylcobalamin:coenzyme M methyltransferase, but also methylates cob(I)alamin with dimethylsulfide, yielding equimolar methylcobalamin and methanethiol in an endergonic reaction with a K(eq) of 5 x 10(-)(4). MtsA and cob(I)alamin mediate dimethylsulfide:coenzyme M methyl transfer in the complete absence of MtsB. Dimethylsulfide inhibited methylcobalamin:coenzyme methyl transfer by MtsA. Inhibition by dimethylsulfide was mixed with respect to methylcobalamin, but competitive with coenzyme M. MtbA, a MtsA homolog participating in coenzyme M methylation with methylamines, was not inhibited by dimethylsulfide and did not catalyze detectable dimethylsulfide:cob(I)alamin methyl transfer. These results are most consistent with a model for the native methylthiol:coenzyme M methyltransferase in which MtsA mediates the methylation of corrinoid bound to MtsB with dimethylsulfide and subsequently demethylates MtsB-bound corrinoid with coenzyme M, possibly employing elements of the same methyltransferase active site for both reactions. << Less

  J. Biol. Chem. 276:4485-4493(2001) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Sequence and transcript analysis of a novel Methanosarcina barkeri methyltransferase II homolog and its associated corrinoid protein homologous to methionine synthase.

  Paul L., Krzycki J.A.

  The sequence and transcript of the genes encoding a recently discovered coenzyme M methylase in Methanosarcina barkeri were analyzed. This 480-kDa protein is composed of two subunits in equimolar concentrations which bind one corrinoid cofactor per alphabeta dimer. The gene for the alphabeta polyp ... >> More

  The sequence and transcript of the genes encoding a recently discovered coenzyme M methylase in Methanosarcina barkeri were analyzed. This 480-kDa protein is composed of two subunits in equimolar concentrations which bind one corrinoid cofactor per alphabeta dimer. The gene for the alphabeta polypeptide, mtsA, is upstream of that encoding the beta polypeptide, mtsB. The two genes are contiguous and overlap by several nucleotides. A 1.9-kb mRNA species which reacted with probes specific for either mtsA or mtsB was detected. Three possible methanogen consensus BoxA sequences as well as two sets of direct repeats were found upstream of mtsA. The 5' end of the mts transcript was 19 nucleotides upstream of the translational start site of mtsA and was positioned 25 bp from the center of the proximal BoxA sequence. The transcript was most abundant in cells grown to the late log phase on acetate but barely detectable in cells grown on methanol or trimethylamine. The amino acid sequence of MtsB was homologous to the cobalamin-binding fragment of methionine synthase from Escherichia coli and possessed the signature residues involved in binding the corrinoid, including a histidyl residue which ligates cobalt. The sequence of MtsA is homologous to the "A" and "M" isozymes of methylcobamide:coenzyme M methyltransferases (methyltransferase II), indicating that the alpha polypeptide is a new member of the methyltransferase II family of coenzyme M methylases. All three methyltransferase II homolog sequences could be aligned with the sequences of uroporphyrinogen decarboxylase from various sources. The implications of these homologies for the mechanism of corrinoid binding by proteins involved in methylotrophic methanogenesis are discussed. << Less

  J. Bacteriol. 178:6599-6607(1996) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.