Linked Life Data

11669645

Source:http://linkedlifedata.com/resource/pubmed/id/11669645

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
43
pubmed:dateCreated
2001-10-23
pubmed:abstractText
Methyl group transfer reactions are essential in methane-forming pathways in all methanogens. The involvement of zinc in catalysis of methyl group transfer was studied for the methyltransferase enzyme MT2-A important for methanogenesis in Methanosarcina barkeri growing on methylamines. Zinc was shown to be required for MT2-A activity and was tightly bound by the enzyme with an apparent stability constant of 10(13.7) at pH 7.2. Oxidation was a factor influencing activity and metal stoichiometry of purified MT2-A preparations. Methods were developed to produce inactive apo MT2-A and to restore full activity with stoichiometric reincorporation of Zn(2+). Reconstitution with Co(2+) yielded an enzyme with 16-fold higher specific activity. Cysteine thiolate coordination in Co(2+)-MT2-A was indicated by high absorptivity in the 300-400 nm charge transfer region, consistent with more than one thiolate ligand at the metal center. Approximate tetrahedral geometry was indicated by strong d-d transition absorbance centered at 622 nm. EXAFS analyses of Zn(2+)-MT2-A revealed 2S + 2N/O coordination with evidence for involvement of histidine. Interaction with the substrate CoM (2-mercaptoethanesulfonic acid) resulted in replacement of the second N/O group with S, indicating direct coordination of the CoM thiolate. UV-visible spectroscopy of Co(2+)-MT2-A in the presence of CoM also showed formation of an additional metal-thiolate bond. Binding of CoM over the range of pH 6.2-7.7 obeyed a model in which metal-thiolate formation occurs separately from H(+) release from the enzyme-substrate complex. Proton release to the solvent takes place from a group with apparent pK(a) of 6.4, and no evidence for metal-thiolate protonation was found. It was determined that substrate metal-thiolate bond formation occurs with a Delta G degrees ' of -6.7 kcal/mol and is a major thermodynamic driving force in the overall process of methyl group transfer.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
40
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
13068-78
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:11669645-Catalysis, pubmed-meshheading:11669645-Cobalt, pubmed-meshheading:11669645-Electrophoresis, Polyacrylamide Gel, pubmed-meshheading:11669645-Escherichia coli, pubmed-meshheading:11669645-Hydrogen Peroxide, pubmed-meshheading:11669645-Hydrogen-Ion Concentration, pubmed-meshheading:11669645-Kinetics, pubmed-meshheading:11669645-Mesna, pubmed-meshheading:11669645-Metals, pubmed-meshheading:11669645-Methanosarcina barkeri, pubmed-meshheading:11669645-Methyltransferases, pubmed-meshheading:11669645-Mutagenesis, Site-Directed, pubmed-meshheading:11669645-Protein Binding, pubmed-meshheading:11669645-Spectrophotometry, pubmed-meshheading:11669645-Sulfhydryl Compounds, pubmed-meshheading:11669645-Thermodynamics, pubmed-meshheading:11669645-Time Factors, pubmed-meshheading:11669645-X-Rays, pubmed-meshheading:11669645-Zinc
pubmed:year
2001
pubmed:articleTitle
Zinc-thiolate intermediate in catalysis of methyl group transfer in Methanosarcina barkeri.
pubmed:affiliation
Department of Biochemistry and Molecular Biology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814-4799, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.