title: Reduction and methyl transfer kinetics of the alpha subunit from acetyl coenzyme a synthase.
abstract: Stopped-flow was used to evaluate the methylation and reduction kinetics of the isolated alpha subunit of acetyl-Coenzyme A synthase from Moorella thermoacetica. This catalytically active subunit contains a novel Ni-X-Fe4S4 cluster and a putative unidentified n = 2 redox site called D. The D-site must be reduced for a methyl group to transfer from a corrinoid-iron-sulfur protein, a key step in the catalytic synthesis of acetyl-CoA. The Fe4S4 component of this cluster is also redox active, raising the possibility that it is the D-site or a portion thereof. Results presented demonstrate that the D-site reduces far faster than the Fe4S4 component, effectively eliminating this possibility. Rather, this component may alter catalytically important properties of the Ni center. The D-site is reduced through a pathway that probably does not involve the Fe4S4 component of this active-site cluster.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station 77843, USA.
authors.forename: Xiangshi
authors.initials: X
authors.lastname: Tan
authors.forename: Christopher
authors.initials: C
authors.lastname: Sewell
authors.forename: Qingwu
authors.initials: Q
authors.lastname: Yang
authors.forename: Paul A
authors.initials: PA
authors.lastname: Lindahl
mesh_terms: D000106:Acetate-CoA Ligase / Q000737:chemistry* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D003001:Cloning, Molecular; D003013:Clostridium / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008745:Methylation; D008780:Methyltransferases / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D008780:Methyltransferases; D000106:Acetate-CoA Ligase