title: Methanol:coenzyme M methyltransferase from Methanosarcina barkeri. Zinc dependence and thermodynamics of the methanol:cob(I)alamin methyltransferase reaction.
abstract: In Methanosarcina barkeri, methanogenesis from methanol is initiated by the formation of methyl-coenzyme M from methanol and coenzyme M. This methyl transfer reaction is catalyzed by two enzymes, designated methyltransferases 1 (MT1) and 2 (MT2). Transferase MT1, which is composed of a 50-kDa subunit, MtaB, and a 27-kDa corrinoid-harbouring subunit, MtaC, has been shown recently to catalyze the methylation of free cob(I)alamin with methanol [Sauer, K., Harms, U. & Thauer, R. K. (1997) Eur. J. Biochem. 243, 670-677]. We report here that this reaction is catalyzed by subunit MtaB overproduced in Escherichia coli. MtaB also catalyzed the formation of methanol from methylcobalamin and H2O, the hydrolysis being associated with a free-energy change deltaG(o)' of approximately +7.0 kJ/mol. MtaB was found to contain 1 mol zinc, and its activity to be zinc dependent (pK(Zn2+) = 9.3). The zinc dependence of the MT2 (MtaA)-catalyzed reaction is also described (pK(Zn2+) = 9.6).
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie and Laboratorium für Mikrobiologie des Fachbereichs Biologie der Philipps-Universität, Marburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Sauer
authors.forename: R K
authors.initials: RK
authors.lastname: Thauer
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D019766:Genes, Archaeal; D007700:Kinetics; D000432:Methanol / Q000378:metabolism; D017021:Methanosarcina barkeri / Q000201:enzymology* / Q000235:genetics; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics; D014805:Vitamin B 12 / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D017931:DNA Primers; D011994:Recombinant Proteins; C019476:mecobalamin; D008780:Methyltransferases; C036890:methanol-2-mercaptoethanesulfonic acid methyltransferase; D015032:Zinc; D014805:Vitamin B 12; D000432:Methanol