JA Krzycki

The Ohio State University, Columbus, Ohio, United States

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Publications (39)151.52 Total impact

  • WT Li · A Mahapatra · DG Longstaff · J Bechtel · G Zhao · PT Kang · MK Chan · JA Krzycki
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    ABSTRACT: Pyrrolysine, the 22nd amino acid, is encoded by amber (TAG=UAG) codons in certain methanogenic archaea and bacteria. PylS, the pyrrolysyl-tRNA synthetase, ligates pyrrolysine to tRNA(Pyl) for amber decoding as pyrrolysine. PylS and tRNA(Pyl) have potential utility in making tailored recombinant proteins. Here, we probed interactions necessary for recognition of substrates by archaeal PylS via synthesis of close pyrrolysine analogs and testing their reactivity in amino acid activation assays. Replacement of the methylpyrroline ring of pyrrolysine with cyclopentane indicated that solely hydrophobic interactions with the ring-binding pocket of PylS are sufficient for substrate recognition. However, a 100-fold increase in the specificity constant of PylS was observed with an analog, 2-amino-6-((R)-tetrahydrofuran-2-carboxamido)hexanoic acid (2Thf-lys), in which tetrahydrofuran replaced the pyrrolysine methylpyrroline ring. Other analogs in which the electronegative atom was moved to different positions suggested PylS preference for a hydrogen-bond-accepting group at the imine nitrogen position in pyrrolysine. 2Thf-lys was a preferred substrate over a commonly employed pyrrolysine analog, but the specificity constant for 2Thf-lys was 10-fold lower than for pyrrolysine itself, largely due to the change in K(m). The in vivo activity of the analogs in supporting UAG suppression in Escherichia coli bearing genes for PylS and tRNA(Pyl) was similar to in vitro results, with L-pyrrolysine and 2Thf-lys supporting the highest amounts of UAG translation. Increasing concentrations of either PylS substrate resulted in a linear increase in UAG suppression, providing a facile method to assay bioactive pyrrolysine analogs. These results illustrate the relative importance of the H-bonding and hydrophobic interactions in the recognition of the methylpyrroline ring of pyrrolysine and provide a promising new series of easily synthesized pyrrolysine analogs that can serve as scaffolds for the introduction of novel functional groups into recombinant proteins.
    No preview · Article · Jan 2009
  • W. Gong · B. Hao · Z. Wei · D. J. Ferguson · T. Tallant · J. A. Krzycki · M. K. Chang
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    ABSTRACT: Ni-dependent carbon monoxide dehydrogenases (Ni-CODHs) are a diverse family of enzymes that catalyze reversible CO:CO oxidoreductase activity in acetogens, methanogens, and some CO-using bacteria. Crystallography of Ni-CODHs from CO-using bacteria and acetogens has revealed the overall fold of the Ni-CODH core and has suggested structures for the C cluster that mediates CO:CO interconversion. Despite these advances, the mechanism of CO oxidation has remained elusive. Herein, we report the structure of a distinct class of Ni-CODH from methanogenic archaea: the component from the CODH/acetyl-CoA decarbonylase/synthase complex, an enzyme responsible for the majority of biogenic methane production on Earth. The structure of this Ni-CODH component provides support for a hitherto unobserved state in which both CO and HO/OH bind to the Ni and the exogenous FCII iron of the C cluster, respectively, and offers insight into the structures and functional roles of the -subunit and FeS domain not present in nonmethanogenic Ni-CODHs.
    No preview · Article · Jan 2009 · Proceedings of the National Academy of Sciences
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    ABSTRACT: Pyrrolysine, the 22nd genetically-encoded amino acid, is charged onto its specific tRNA by PylS, a pyrrolysyl-tRNA synthetase. While PylS is found as a single protein in certain archaeal methanogens, in the gram-positive bacterium Desulfitobacterium hafniense, PylS is divided into two separate proteins, PylSn and PylSc, corresponding to the N-terminal and C-terminal domains of the single PylS protein found in methanogens. Previous crystallographic studies have provided the structure of a truncated C-terminal portion of the archaeal Methanosarcina mazei PylS associated with catalysis. Here, we report the apo 2.1A resolution structure of the intact D. hafniense PylSc protein and compare it to structures of the C-terminal truncated PylS from methanogenic species. In PylSc, the hydrophobic pocket binding the ring of pyrrolysine is more constrained than in the archaeal enzyme; other structural differences are also apparent.
    Preview · Article · Sep 2008 · Biochemical and Biophysical Research Communications

  • No preview · Article · Jun 2005

  • No preview · Article · Sep 2004 · Chemtracts
  • B Hao · W Gong · TK Ferguson · CM James · JA Krzycki · MK Chan
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    ABSTRACT: Genes encoding methanogenic methylamine methyltransferases all contain an in-frame amber (UAG) codon that is read through during translation. We have identified the UAG-encoded residue in a 1.55 angstrom resolution structure of the Methanosarcina barkeri monomethylamine methyltransferase (MtmB). This structure reveals a homohexamer comprised of individual subunits with a TIM barrel fold. The electron density for the UAG-encoded residue is distinct from any of the 21 natural amino acids. Instead it appears consistent with a lysine in amide-linkage to (4R,5R)-4-substituted-pyrroline-5-carboxylate. We suggest that this amino acid be named l-pyrrolysine.
    No preview · Article · Jan 2002
  • G Srinivasan · CM James · JA Krzycki
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    ABSTRACT: Pyrrolysine is a lysine derivative encoded by the UAG codon in methylamine methyltransferase genes of Methanosarcina barkeri. Near a methyltransferase gene cluster is the pylT gene, which encodes an unusual transfer RNA (tRNA) with a CUA anticodon. The adjacent pylS gene encodes a class II aminoacyl-tRNA synthetase that charges the pylT-derived tRNA with lysine but is not closely related to known lysyl-tRNA synthetases. Homologs of pylS and pylT are found in a Gram-positive bacterium. Charging a tRNA(CUA) with lysine is a likely first step in translating UAG amber codons as pyrrolysine in certain methanogens. Our results indicate that pyrrolysine is the 22nd genetically encoded natural amino acid.
    No preview · Article · Jan 2002
  • C M James · T K Ferguson · J F Leykam · JA Krzycki
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    ABSTRACT: Each of the genes encoding the methyltransferases initiating methanogenesis from trimethylamine, dimethylamine, or monomethylamine by various Methanosarcina species possesses one naturally occurring in-frame amber codon that does not appear to act as a translation stop during synthesis of the biochemically characterized methyltransferase. To investigate the means by which suppression of the amber codon within these genes occurs, MtmB, a methyltransferase initiating metabolism of monomethylamine, was examined. The C-terminal sequence of MtmB indicated that synthesis of this mtmB1 gene product did not cease at the internal amber codon, but at the following ochre codon. Antibody raised against MtmB revealed that Escherichia coli transformed with mtmB1 produced the amber termination product. The same antibody detected primarily a 50-kDa protein in Methanosarcina barkeri, which is the mass predicted for the amber readthrough product of the mtmB1 gene. Sequencing of peptide fragments from MtmB by Edman degradation and mass spectrometry revealed no change in the reading frame during mtmB1 expression. The amber codon position corresponded to a lysyl residue using either sequencing technique. The amber codon is thus read through during translation at apparently high efficiency and corresponds to lysine in tryptic fragments of MtmB even though canonical lysine codon usage is encountered in other Methanosarcina genes.
    No preview · Article · Oct 2001 · Journal of Biological Chemistry
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    Thomas C. Tallant · Ligi Paul · JA Krzycki
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    ABSTRACT: 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.
    Preview · Article · Mar 2001 · Journal of Biological Chemistry
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    ABSTRACT: Methyl transfer from dimethylamine to coenzyme M was reconstituted in vitro for the first time using only highly purified proteins. These proteins isolated from Methanosarcina barkeri included the previously unidentified corrinoid protein MtbC, which copurified with MtbA, the methylcorrinoid:Coenzyme M methyltransferase specific for methanogenesis from methylamines. MtbC binds 1.0 mol of corrinoid cofactor/mol of 24-kDa polypeptide and stimulated dimethylamine:coenzyme M methyl transfer 3.4-fold in a cell extract. Purified MtbC and MtbA were used to assay and purify a dimethylamine:corrinoid methyltransferase, MtbB1. MtbB1 is a 230-kDa protein composed of 51-kDa subunits that do not possess a corrinoid prosthetic group. Purified MtbB1, MtbC, and MtbA were the sole protein requirements for in vitro dimethylamine:coenzyme M methyl transfer. An MtbB1:MtbC ratio of 1 was optimal for coenzyme M methylation with dimethylamine. MtbB1 methylated either corrinoid bound to MtbC or free cob(I)alamin with dimethylamine, indicating MtbB1 carries an active site for dimethylamine demethylation and corrinoid methylation. Experiments in which different proteins of the resolved monomethylamine:coenzyme M methyl transfer reaction replaced proteins involved in dimethylamine:coenzyme M methyl transfer indicated high specificity of MtbB1 and MtbC in dimethylamine:coenzyme M methyl transfer activity. These results indicate MtbB1 demethylates dimethylamine and specifically methylates the corrinoid prosthetic group of MtbC, which is subsequently demethylated by MtbA to methylate coenzyme M during methanogenesis from dimethylamine.
    No preview · Article · Oct 2000 · Journal of Biological Chemistry
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    SA Burke · S L Lo · JA Krzycki
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    ABSTRACT: Coenzyme M (CoM) is methylated during methanogenesis from monomethyamine in a reaction catalyzed by three proteins. Using monomethylamine, a 52-kDa polypeptide termed monomethylamine methyltransferase (MMAMT) methylates the corrinoid cofactor bound to a second polypeptide, monomethylamine corrinoid protein (MMCP). Methylated MMCP then serves as a substrate for MT2-A, which methylates CoM. The genes for these proteins are clustered on 6.8 kb of DNA in Methanosarcina barkeri MS. The gene encoding MMCP (mtmC) is located directly upstream of the gene encoding MMAMT (mtmB). The gene encoding MT2-A (mtbA) was found 1.1 kb upstream of mtmC, but no obvious open reading frame was found in the intergenic region between mtbA and mtmC. A single monocistronic transcript was found for mtbA that initiated 76 bp from the translational start. Separate transcripts of 2.4 and 4.7 kb were detected, both of which carried mtmCB. The larger transcript also encoded mtmP, which is homologous to the APC family of cationic amine permeases and may therefore encode a methylamine permease. A single transcriptional start site was found 447 bp upstream of the translational start of mtmC. MtmC possesses the corrinoid binding motif found in corrinoid proteins involved in dimethylsulfide- and methanol-dependent methanogenesis, as well as in methionine synthase. The open reading frame of mtmB was interrupted by a single in-frame, midframe, UAG codon which was also found in mtmB from M. barkeri NIH. A mechanism that circumvents UAG-directed termination of translation must operate during expression of mtmB in this methanogen.
    Preview · Article · Aug 1998 · Journal of Bacteriology
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    T C Tallant · J A Krzycki
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    ABSTRACT: During growth on acetate, Methanosarcina barkeri expresses catabolic enzymes for other methanogenic substrates such as monomethylamine. The range of substrates used by cells grown on acetate was further explored, and it was found that cells grown on acetate also converted dimethylsulfide (DMS) and methylmercaptopropionate (MMPA) to methane. Cells or extracts of cells grown on trimethylamine or methanol did not utilize either DMS or MMPA. During growth on acetate, cultures demethylated MMPA, producing methane and mercaptopropionate. Extracts of acetate-grown cells possessed DMS- and MMPA-dependent coenzyme M (CoM) methylation activities. The activity peaks of CoM methylation with either DMS or MMPA coeluted upon gel permeation chromatography of extracts of acetate-grown cells consistent with an apparent molecular mass of 470 kDa. A 480-kDa corrinoid protein, previously demonstrated to be a CoM methylase but otherwise of unknown physiological function, was found to methylate CoM with either DMS or MMPA. MMPA was demethylated by the purified 480-kDa CoM methylase, consuming 1 mol of CoM and producing 1 mol of mercaptopropionate. DMS was demethylated by the purified protein, consuming 1 mol of CoM and producing 1 mol of methanethiol. The methylthiol:CoM methyltransferase reaction could be initiated only with the enzyme-bound corrinoid in the methylated state. CoM could demethylate, and DMS and MMPA could remethylate, the corrinoid cofactor. The monomethylamine corrinoid protein and the A isozyme of methylcobamide:CoM methyltransferase (proteins homologous to the two subunits comprising the 480-kDa CoM methylase) did not catalyze CoM methylation with methylated thiols. These results indicate that the 480-kDa corrinoid protein functions as a CoM methylase during methanogenesis from DMS or MMPA.
    Preview · Article · Dec 1997 · Journal of Bacteriology
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    D. J. Jr Ferguson · JA Krzycki
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    ABSTRACT: Reconstitution of trimethylamine-dependent coenzyme M (CoM) methylation was achieved with three purified polypeptides. Two of these polypeptides copurified as a trimethylamine methyl transfer (TMA-MT) activity detected by stimulation of the TMA:CoM methyl transfer reaction in cell extracts. The purified TMA-MT fraction stimulated the rate of methyl-CoM formation sevenfold, up to 1.7 micromol/min/mg of TMA-MT protein. The TMA-MT polypeptides had molecular masses of 52 and 26 kDa. Gel permeation of the TMA-MT fraction demonstrated that the 52-kDa polypeptide eluted with an apparent molecular mass of 280 kDa. The 26-kDa protein eluted primarily as a monomer, but some 26-kDa polypeptides also eluted with the 280-kDa peak, indicating that the two proteins weakly associate. The two polypeptides could be completely separated using gel permeation in the presence of sodium dodecyl sulfate. The corrinoid remained associated with the 26-kDa polypeptide at a molar ratio of 1.1 corrin/26-kDa polypeptide. This polypeptide was therefore designated the TMA corrinoid protein, or TCP. The TMA-MT polypeptides, when supplemented with purified methylcorrinoid:CoM methyltransferase (MT2), could effect the demethylation of TMA with the subsequent methylation of CoM and the production of dimethylamine at specific activities of up to 600 nmol/min/mg of TMA-MT protein. Neither dimethylamine nor monomethylamine served as the substrate, and the activity required Ti(III) citrate and methyl viologen. TMA-MT could interact with either isozyme of MT2 but had the greatest affinity for the A isozyme. These results suggest that TCP is uniquely involved in TMA-dependent methanogenesis, that this corrinoid protein is methylated by the substrate and demethylated by either isozyme of MT2, and that the predominant isozyme of MT2 found in TMA-grown cells is the favored participant in the TMA:CoM methyl transfer reaction.
    Full-text · Article · Mar 1997 · Journal of Bacteriology
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    L Paul · J A Krzycki
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    ABSTRACT: 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.
    Preview · Article · Dec 1996 · Journal of Bacteriology
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    D. J. Jr Ferguson · JA Krzycki · DA Grahame
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    ABSTRACT: An immunochemical approach was employed as a direct test for functional activities of isozymes of methylcobamide:coenzyme M methyltransferase (MT2-M and MT2-A) in the metabolic pathways of methane formation from: methanol, acetate, monomethylamine, dimethylamine, and trimethylamine. Specific removal of the MT2 isozymes from buffer soluble cell extracts of Methanosarcina barkeri was accomplished by use of immobilized, affinity-purified, ovine polyclonal antibodies. Extracts of methanol-grown cells depleted of MT2-M lost entirely the ability to carry out conversion of methanol to 2-(methylthio)ethanesulfonate (methyl-CoM). Methanol:CoM methyl transfer activity was completely restored by addition of purified MT2-M, but no activity was recovered by addition of MT2-A. In contrast, the activity of trimethylamine-grown cell extracts to convert monomethylamine and dimethylamine to methyl-CoM was lost almost entirely by immunosorptive removal of MT2-A. Addition of purified MT2-A, but not MT2-M, to the MT2-A-depleted extract fully reconstituted methyl-CoM formation from both mono- and dimethylamine. Interestingly, in extracts resolved of MT2-A, trimethylamine-dependent methylation of coenzyme M was observed at approximately 20% of the rate of controls not treated with antibody. Furthermore, both isozymes were effective in full restoration of trimethylamine conversion. Tests indicated that neither of the two MT2 isozymes are involved in methane formation from acetate. The results establish that MT2-A plays a specific role in metabolism of methylated amine substrates, whereas, MT2-M functions in methane formation from trimethylamine and methanol.
    Full-text · Article · Apr 1996 · Journal of Biological Chemistry
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    T C Tallant · JA Krzycki
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    ABSTRACT: Activity staining of extracts of Methanosarcina barkeri electrophoresed in polyacrylamide gels revealed an additional methylcobalamin:coenzyme M (methylcobalamin:CoM) methyltransferase present in cells grown on acetate but not in those grown on trimethylamine. This methyltransferase is the 480-kDa corrinoid protein previously identified by its methylation following inhibition of methyl-CoM reductase in otherwise methanogenic cell extracts. The methylcobalamin:CoM methyltransferase activity of the purified 480-kDa protein increased from 0.4 to 3.8 micromol/min/mg after incubation with sodium dodecyl sulfate (SDS). Following SDS-polyacrylamide gel electrophoresis analysis of unheated protein samples, a polypeptide with an apparent molecular mass of 48 kDa which possessed methylcobalamin:CoM methyltransferase activity was detected. This polypeptide migrated with an apparent mass of 41 kDa when the 480-kDa protein was heated before electrophoresis, indicating that the alpha subunit is responsible for the activity. The N-terminal sequence of this subunit was 47% similar to the N termini of the A and M isozymes of methylcobalamin:CoM methyltransferase (methyltransferase II). The endogenous methylated corrinoid bound to the beta subunit of the 480-kDa protein could be demethylated by CoM, but not by homocysteine or dithiothreitol, resulting in a Co(I) corrinoid. The Co(I) corrinoid could be remethylated by methyl iodide, and the protein catalyzed a methyl iodide:CoM transmethylation reaction at a rate of 2.3 micromol/min/mg. Methyl-CoM was stoichiometrically produced from CoM, as demonstrated by high-pressure liquid chromatography with indirect photometric detection. Two thiols, 2-mercaptoethanol and mercapto-2-propanol, were poorer substrates than CoM, while several others tested (including 3-mercaptopropanesulfonate) did not serve as methyl acceptors. These data indicate that the 480-kDa corrinoid protein is composed of a novel isozyme of methyltransferase II which remains firmly bound to a corrinoid cofactor binding subunit during isolation.
    Preview · Article · Apr 1996 · Journal of Bacteriology
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    SA Burke · JA Krzycki
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    ABSTRACT: An assay which allowed detection of proteins involved in the trimethylamine- or monomethylamine (MMA)-dependent methylation of coenzyme M (CoM) was developed. The two activities could be separated by anion-exchange chromatography. The unresolved activity responsible for MMA:CoM methyl transfer eluted from a gel permeation column in the molecular mass range of 32 kDa. The activity was purified to two monomeric proteins of 40 and 29 kDa. The preparation contained protein-bound corrinoid in a mixture of Co(II) and Co(III) states, as well as methyl-B12:CoM methyltransferase (MT2) activity. N-terminal sequence analysis demonstrated that the polypeptides were two previously identified proteins of undefined physiological function. The smaller polypeptide was the monomeric 29-kDa corrinoid protein. The larger polypeptide was the "A" isozyme of MT2. Individually purified preparations of both proteins increased the rate of MMA-dependent CoM methylation by approximately 1.7 mumol/min/mg of purified protein above background activity in the extract of methanol-grown cells. These results indicate that the 29-kDa corrinoid protein and the "A" isozyme of MT2 function in methanogenesis from MMA. A likely mechanism is that the 29-kDa corrinoid is methylated by MMA and the methyl group is then transferred by the "A" isozyme of MT2 to CoM.
    Preview · Article · Sep 1995 · Journal of Bacteriology
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    J Kremer · S Burchfield · C Frazier · J Krzycki
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    ABSTRACT: The 480-kDa corrinoid protein was significantly methylated in extracts of acetate- but not methanol-grown cells incubated with 14CH3OH, in part because of its decreased synthesis in cells grown on substrates other than acetate. In addition, a 200-kDa corrinoid protein was methylated in extracts of methanol- but not acetate-grown cells.
    Preview · Article · Feb 1994 · Journal of Bacteriology
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    J D Kremer · X Cao · J Krzycki
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    ABSTRACT: Two corrinoid proteins with molecular sizes of 480 and 29 kDa are stably methylated by [2-14C]acetate-derived intermediates in cell extracts of aceticlastic Methanosarcina barkeri when methylreductase is inhibited by the addition of bromoethanesulfonic acid. Both 14CH3-proteins have been isolated to near homogeneity and found to be abundant soluble proteins. The larger protein possesses two subunits, of 41.4 and 30.4 kDa, in an equimolar ratio, suggesting an alpha 6 beta 6 conformation with six bound methylated corrinoids per 480-kDa molecule. The 29-kDa protein is a monomer in solution and possesses only one methylated corrinoid. All methyl groups on both proteins are photolabile, but the methylated corrinoid bound to the 29-kDa protein undergoes photolysis at a higher rate than that bound to the 480-kDa protein. The two proteins possess discrete N termini and do not appear to be forms of the same protein in equilibrium. Neither protein has an Fe4S4 cluster, and both have UV-visible spectra most similar to that of a base-on methylated corrinoid. A previously identified methylated protein, designated the unknown A 14CH3-protein, copurifies with the 480-kDa protein and has the same subunit composition. The methyl groups of both isolated 14CH3-proteins are converted to methane in cell extracts. The methylated proteins that accumulate in extracts in the presence of bromoethanesulfonic acid are demethylated by the addition of coenzyme M. Both isolated proteins are abundant novel corrinoid proteins that can methylate and be methylated by intermediates of the methanogenic pathway.
    Preview · Article · Sep 1993 · Journal of Bacteriology
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    X J Cao · J A Krzycki
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    ABSTRACT: Corrinoid proteins have been implicated as methyl carriers in methane formation from acetate, yet specific corrinoid proteins methylated by acetate-derived intermediates have not been identified. In the presence of ATP, H2, and bromoethanesulfonic acid, label from 3H- or 2-14C-labeled acetate was incorporated into the protein fraction of cell extracts of Methanosarcina barkeri. Incorporated label was susceptible to photolysis, yielding labeled methane as the anaerobic photolysis product. Size exclusion high-pressure liquid chromatography (HPLC) demonstrated the presence of at least three labeled proteins with native molecular sizes of 480, 200, and 29 kDa, while electrophoresis indicated that four major labeled proteins were present. Dual-label experiments demonstrated that these four proteins were methylated rather than acetylated. Two of the proteins (480 and 29 kDa) contained the majority of radiolabel and were stably methylated. After labeling with [2-14C]acetate, the stable 14CH3-proteins were partially purified, and 14CH3-cofactors were isolated from each protein. UV-visible spectroscopy and HPLC demonstrated these to be methylated corrinoids. When the 480-kDa corrinoid protein was purified to 70% homogeneity, the preparation was found to have subunits of 40 and 30 kDa. The 480-kDa protein but not the 29-kDa protein was methylated during in vitro methanogenesis from acetate and demethylated as methanogenesis ceased, consistent with the involvement of this protein in methane formation.
    Preview · Article · Oct 1991 · Journal of Bacteriology

Publication Stats

2k Citations
151.52 Total Impact Points


  • 1989-2008
    • The Ohio State University
      • Department of Microbiology
      Columbus, Ohio, United States
  • 1987
    • Michigan State University
      East Lansing, Michigan, United States
  • 1980-1987
    • University of Wisconsin, Madison
      • Department of Bacteriology
      Mississippi, United States