On the structure of the nickel/iron/sulfur center of the carbon monoxide dehydrogenase from Rhodospirillum rubrum: an x-ray absorption spectroscopy study.
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.
Tan
G O
GO
Department of Chemistry, Stanford University, CA 94305.
Ensign
S A
SA
Ciurli
S
S
Scott
M J
MJ
Hedman
B
B
Holm
R H
RH
Ludden
P W
PW
Korszun
Z R
ZR
Stephens
P J
PJ
Hodgson
K O
KO
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
D009097:Multienzyme Complexes; D013455:Sulfur; D009532:Nickel; D007501:Iron; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase