Structural investigations by extended X-ray absorption fine structure spectroscopy of the iron center of mitochondrial aconitase in higher plant cells.
We have obtained iron K-edge extended x-ray absorption fine structure spectra of the plant mitochondrial aconitase in its active state, in the presence (aconitase (+)) and absence (aconitase (-)) of the substrate citrate. Analysis of the data indicates that oxygens are present in the first coordination shell, at an average Fe-O distance of 1.96/1.98 A (aconitase (+)/aconitase(-)). Part of these oxygens is provided by the citrate, which binds at 1.99 A from the iron in aconitase (+). The second shell (sulfur) contribution is split and is consistent with Fe-S distances of 2.30/2.29 and 2.56/2.59 A, and the third shell (iron) is consistent with an Fe-Fe distance of 2.83/2.84 A. Both Fe-S and Fe-Fe distances are longer than similar distances found in most Fe-S centers. A strong scattering at approximately 5 A has been identified as originating from an iron atom which is near to, but not part of, the Fe-S cluster. These data indicate that active plant mitochondrial aconitase contains a novel type of iron center.
Jordanov
J
J
Centre National de la Recherche Scientifique, URA 576, Département de Biologie Moléculaire et Structurale, Grenoble, France.
Courtois-Verniquet
F
F
Neuburger
M
M
Douce
R
R
D000154:Aconitate Hydratase / Q000737:chemistry*; D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000032:analysis; D008928:Mitochondria / Q000201:enzymology*; D011487:Protein Conformation; D011198:Solanum tuberosum / Q000201:enzymology*; D013057:Spectrum Analysis / Q000379:methods
D007501:Iron; D000154:Aconitate Hydratase