title: Activation mechanism of methanol:5-hydroxybenzimidazolylcobamide methyltransferase from Methanosarcina barkeri.
abstract: Methanol:5-hydroxybenzimidazolylcobamide methyltransferase (MT1) is the first of two enzymes involved in the transmethylation reaction from methanol to 2-mercaptoethanesulfonic acid in Methanosarcina barkeri. MT1 only binds the methyl group of methanol when the cobalt atom of its corrinoid prosthetic groups is present in the highly reduced Co(I) state. Formation of this redox state requires H2, hydrogenase, methyltransferase activation protein, and ATP. Optical and electron paramagnetic resonance spectroscopy studies were employed to determine the oxidation states and coordinating ligands of the corrinoids of MT1 during the activation process. Purified MT1 contained 1.7 corrinoids per enzyme with cobalt in the fully oxidized Co(III) state. Water and N-3 of the 5-hydroxybenzimidazolyl base served as the upper and lower ligands, respectively. Reduction to the Co(II) level was accomplished by H2 and hydrogenase. The cob(II)amide of MT1 had the base coordinated at this stage. Subsequent addition of methyltransferase activation protein and ATP resulted in the formation of base-uncoordinated Co(II) MT1. The activation mechanism is discussed within the context of a proposed model and compared to those described for other corrinoid-containing methyl group transferring proteins.
authors.affiliation: Department of Microbiology, Faculty of Science, University of Nijmegen, Toernooiveld, NL-6525 ED Nijmegen, The Netherlands.
authors.forename: P J
authors.initials: PJ
authors.lastname: Daas
authors.forename: W R
authors.initials: WR
authors.lastname: Hagen
authors.forename: J T
authors.initials: JT
authors.lastname: Keltjens
authors.forename: C
authors.initials: C
authors.lastname: van der Drift
authors.forename: G D
authors.initials: GD
authors.lastname: Vogels
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D019843:Archaeal Proteins; D003035:Cobalt / Q000378:metabolism; D045728:Corrinoids; D004578:Electron Spin Resonance Spectroscopy; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D017021:Methanosarcina barkeri / Q000201:enzymology*; D008780:Methyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011166:Porphyrins / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
chemical_list: D019843:Archaeal Proteins; D045728:Corrinoids; D011166:Porphyrins; D003035:Cobalt; D000255:Adenosine Triphosphate; D008780:Methyltransferases; C040528:methanol-5-hydroxybenzimidazolylcobamide methyltransferase; D011494:Protein Kinases; C101667:methyltransferase activation protein, Methanosarcina barkeri