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, Thomas C.; Paul, Ligi; Krzycki, Joseph A.

doi:10.1074/jbc.m007514200

Cited by 73 publications

(57 citation statements)

References 49 publications

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“…Corrinoid-carrying subunits from Methanosarcina species involved in methyl transfer to coenzyme M from monomethylamine, dimethylamine, and trimethylamine, respectively (31)(32)(33), lack this extension and are not purified in complex with the corresponding methyltransferases (29,31,34). In contrast, the corrinoid protein involved in methyl-coenzyme M formation from coenzyme M and dimethylsulfide contains an N-terminal extension and is purified in a tight complex with its methyltransferase (35).…”

Section: Resultsmentioning

confidence: 96%

Insight into the mechanism of biological methanol activation based on the crystal structure of the methanol-cobalamin methyltransferase complex

Hagemeier

Kr̈er

Thauer

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Some methanogenic and acetogenic microorganisms have the catalytic capability to cleave heterolytically the COO bond of methanol. To obtain insight into the elusive enzymatic mechanism of this challenging chemical reaction we have investigated the methanol-activating MtaBC complex from Methanosarcina barkeri composed of the zinc-containing MtaB and the 5-hydroxybenzimidazolylcobamide-carrying MtaC subunits. Here we report the 2.5-Å crystal structure of this complex organized as a (MtaBC) 2 heterotetramer. MtaB folds as a TIM barrel and contains a novel zinc-binding motif. Zinc(II) lies at the bottom of a funnel formed at the Cterminal ␤-barrel end and ligates to two cysteinyl sulfurs (Cys-220 and Cys-269) and one carboxylate oxygen (Glu-164). MtaC is structurally related to the cobalamin-binding domain of methionine synthase. Its corrinoid cofactor at the top of the Rossmann domain reaches deeply into the funnel of MtaB, defining a region between zinc(II) and the corrinoid cobalt that must be the binding site for methanol. The active site geometry supports a S N 2 reaction mechanism, in which the COO bond in methanol is activated by the strong electrophile zinc(II) and cleaved because of an attack of the supernucleophile cob(I)amide. The environment of zinc(II) is characterized by an acidic cluster that increases the charge density on the zinc(II), polarizes methanol, and disfavors deprotonation of the methanol hydroxyl group. Implications of the MtaBC structure for the second step of the reaction, in which the methyl group is transferred to coenzyme M, are discussed.conformational change ͉ methanol metabolism ͉ x-ray structure ͉ zinc M ethanol is an abundant C 1 -compound in nature. Its major source is probably the plant cell wall component pectin from which methanol is released upon hydrolytic degradation. In oxic environments methanol is rapidly metabolized to CO 2 by aerobic methylotrophic microorganisms, which thereby prevents autooxidation to the cytotoxic formaldehyde (1). Methanol also does not accumulate in anaerobic environments, where methanogenic archaea (2) and acetogenic bacteria (3) reduce the C 1 -compound to methane, carbonylate it to acetate, and/or oxidize it to CO 2 in their energy metabolism.Methanol metabolism is initiated in methanogenic archaea by its reaction with coenzyme M (HS-CoM) to form methyl-coenzyme M (CH 3 -S-CoM) (reaction 1) (4, 5). Methyl-coenzyme M is the central intermediate for reduction to methane and oxidation to CO 2 .

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Section: Resultsmentioning

confidence: 96%

Insight into the mechanism of biological methanol activation based on the crystal structure of the methanol-cobalamin methyltransferase complex

Hagemeier

Kr̈er

Thauer

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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“…One could imagine that this is simply a consequence of having the capacity to utilize methysulphides for methanogenesis. Transfer of methyl groups from methylsulphides to CoM is freely reversible (Tallant and Krzycki, 1997;Tallant et al, 2001). Thus, because CH 3-CoM is an intermediate in all known methanogenic pathways and because sulphide is ubiquitous in the anaerobic environments where these methanogens live, low levels of any of the Mts proteins could result in production of DMS, which in turn would trigger the positive feedback loop.…”

Section: Discussionmentioning

confidence: 99%

“…A methylthiol:CoM methyltransferase enzyme that allows M. barkeri MS to demethylate DMS has been characterized. It consists of a single methyltransferase (MtsA) and a corrinoid protein (MtsB) that catalyses the transfer of a methyl group from DMS to CoM (Tallant and Krzycki, 1997;Tallant et al, 2001). Although homologues for the MtsA/B system are present in M. barkeri Fusaro and Methanosarcina mazei Gö1, they are absent in M. acetivorans C2A.…”

Section: Introductionmentioning

confidence: 99%

Regulation of putative methyl‐sulphide methyltransferases in Methanosarcina acetivorans C2A

Bose

Kulkarni

Metcalf

2009

Molecular Microbiology

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SummaryThe regulation of the Methanosarcina acetivorans mtsD, mtsF and mtsH genes, which encode putative corrinoid/methyltransferase isozymes involved in methylsulphide metabolism, was examined by a variety of methods, suggesting that their expression is regulated at both the transcriptional and posttranscriptional levels. Transcripts of all three genes, measured by quantitative reverse transcription PCR, were shown to be most abundant during growth on methanol with dimethylsulphide (DMS). Transcript levels were also high in media with CO or methylamines, but much lower with methanol. In contrast, translational fusions to mtsD showed high expression levels on CO or methanol with DMS, while the mtsF translational fusion showed highest reporter gene activity on methylamines with much lower expression on CO or methanol with DMS. The activity of mtsD and mtsF fusions was very low when the strains were grown in methanol or acetate. Expression of the mtsH fusion was not detected on any substrate, despite the presence of an mRNA transcript. The transcription start sites of all three genes were determined by 5Ј-RACE revealing large leader sequences for each transcript. Characterization of deletion mutants lacking putative regulatory genes suggests that MA0862 (msrF), MA4383 (msrC) and MA4560 (msrG) act as transcriptional activators of mtsD, mtsF and mtsH respectively.

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“…Under the condition of DMS production, the methyl group is transferred from methyl-CoM to MT, a reaction that is the reverse of the CoM methylation step employed by DMS-consuming methanogens (Hedderich and Whitman, 2006). As Moran et al (2008) pointed out, such a shortcut to regenerate CoM-SH is feasible, owing to the low energy barrier in the activation step of methanogenic DMS consumption by methylthiol:CoM methyltransferase (Mts) ( G • = 0.35 kJ per reaction; Tallant et al, 2001). The overall energy yield for the methanogenic DMS production is theoretically lower than normal methanogenesis, as the H + -pumping step of heterodisulfide reduction is bypassed and energy conservation is restricted to the Na + -pumping Mtr complex (Hedderich and Whitman, 2006).…”

Section: Microbial Dms Formationmentioning

confidence: 99%

Microbial conversion of inorganic carbon to dimethyl sulfide in anoxic lake sediment (Plußsee, Germany)

et al. 2010

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Abstract. In anoxic environments, volatile methylated sulfides like methanethiol (MT) and dimethyl sulfide (DMS) link the pools of inorganic and organic carbon with the sulfur cycle. However, direct formation of methylated sulfides from reduction of dissolved inorganic carbon has previously not been demonstrated. When studying the effect of temperature on hydrogenotrophic microbial activity, we observed formation of DMS in anoxic sediment of Lake Plußsee at 55 • C. Subsequent experiments strongly suggested that the formation of DMS involves fixation of bicarbonate via a reductive pathway in analogy to methanogenesis and engages methylation of MT. DMS formation was enhanced by addition of bicarbonate and further increased when both bicarbonate and H 2 were supplemented. Inhibition of DMS formation by 2-bromoethanesulfonate points to the involvement of methanogens. Compared to the accumulation of DMS, MT showed the opposite trend but there was no apparent 1:1 stoichiometric ratio between both compounds. Both DMS and MT had negative δ 13 C values of −62‰ and −55‰, respectively. Labeling with NaH 13 CO 3 showed more rapid incorporation of bicarbonate into DMS than into MT. The stable carbon isotopic evidence implies that bicarbonate was fixed via a reductive pathway of methanogenesis, and the generated methyl coenzyme M became the methyl donor for MT methylation. Neither DMS nor MT accumulation were stimulated by addition of the methyl-group donors methanol and syringic acid or by the methyl-group acceptor hydrogen sulphide. The source of MT was further investigated in a H 35 2 S labeling experiment, which demonstrated a microbially-mediated process of hydrogen sulfide methyCorrespondence to: Y. S. Lin (yushih@uni-bremen.de) lation to MT that accounted for only <10% of the accumulation rates of DMS. Therefore, the major source of the 13 C-depleted MT was neither bicarbonate nor methoxylated aromatic compounds. Other possibilities for isotopically depleted MT, such as other organic precursors like methionine, are discussed. This DMS-forming pathway may be relevant for anoxic environments such as hydrothermally influenced sediments and fluids and sulfate-methane transition zones in marine sediments.

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The MtsA Subunit of the Methylthiol:Coenzyme M Methyltransferase of Methanosarcina barkeri Catalyses Both Half-reactions of Corrinoid-dependent Dimethylsulfide: Coenzyme M Methyl Transfer

Cited by 73 publications

References 49 publications

Insight into the mechanism of biological methanol activation based on the crystal structure of the methanol-cobalamin methyltransferase complex

Insight into the mechanism of biological methanol activation based on the crystal structure of the methanol-cobalamin methyltransferase complex

Regulation of putative methyl‐sulphide methyltransferases in Methanosarcina acetivorans C2A

Microbial conversion of inorganic carbon to dimethyl sulfide in anoxic lake sediment (Plußsee, Germany)

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