title: On the structure of the nickel/iron/sulfur center of the carbon monoxide dehydrogenase from Rhodospirillum rubrum: an x-ray absorption spectroscopy study.
abstract: The nickel/iron/sulfur center of the carbon monoxide dehydrogenase (carbon monoxide:(acceptor)oxidoreductase; EC 1.2.99.2) enzyme from Rhodospirillum rubrum (Rr-CODH) was studied by x-ray absorption spectroscopy at the Ni K edge. Extended x-ray absorption fine structure data show that the first Ni coordination shell consists of 2 S atoms at 2.23 A and 2-3 N/O atoms at 1.87 A. The edge structure indicates a distorted tetrahedral or five-coordinate Ni environment in both oxidized and reduced Rr-CODH. By comparing second-shell extended x-ray absorption fine structure data of Rr-CODH to that of (Et4N)3[NiFe3S4(SEt)4], a cubane-type cluster, it was clearly established that Ni in the Rr-CODH center is not involved in the core of a NiFe3S4 cubane cluster. One model consistent with the results is a mononuclear Ni2+ site, bridged by S-Cys or sulfide to one or both of the Fe4S4 clusters of the enzyme, with the remaining coordination sites occupied by additional S-Cys or N/O-liganding amino acid residues.
authors.affiliation: Department of Chemistry, Stanford University, CA 94305.
authors.forename: G O
authors.initials: GO
authors.lastname: Tan
authors.forename: S A
authors.initials: SA
authors.lastname: Ensign
authors.forename: S
authors.initials: S
authors.lastname: Ciurli
authors.forename: M J
authors.initials: MJ
authors.lastname: Scott
authors.forename: B
authors.initials: B
authors.lastname: Hedman
authors.forename: R H
authors.initials: RH
authors.lastname: Holm
authors.forename: P W
authors.initials: PW
authors.lastname: Ludden
authors.forename: Z R
authors.initials: ZR
authors.lastname: Korszun
authors.forename: P J
authors.initials: PJ
authors.lastname: Stephens
authors.forename: K O
authors.initials: KO
authors.lastname: Hodgson
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000445:Aldehyde Oxidoreductases / Q000737:chemistry*; D001665:Binding Sites; D007501:Iron / Q000032:analysis; D009097:Multienzyme Complexes; D009532:Nickel / Q000032:analysis; D010084:Oxidation-Reduction; D011487:Protein Conformation; D012247:Rhodospirillum rubrum / Q000201:enzymology*; D013455:Sulfur / Q000032:analysis
chemical_list: D009097:Multienzyme Complexes; D013455:Sulfur; D009532:Nickel; D007501:Iron; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase