The iron ligand sphere geometry of mammalian 15-lipoxygenases.
We investigated the geometry of the iron ligand sphere of the native rabbit 15-lipoxygenase (15-LOX) by X-ray absorption spectroscopy using synchrotron radiation. The soybean LOX-1 was used as a reference compound because its iron ligand sphere is well characterized. For structural information the X-ray absorption spectra were evaluated using the Excurve Program (CCLRC Daresbury Laboratory, Warrington, U.K.). From the positions of the absorption edges and from the intensities of the 1s-3d pre-edge transition peaks a six-coordinate ferrous iron was concluded for the rabbit 15-LOX. Evaluation of the extended region of the absorption spectra suggested six nitrogen and/or oxygen atoms as direct iron ligands, and the following binding distances were determined (means+/-S.D.; estimated accuracy is +/-0.001nm for bond distances, on the basis of more than 22 X-ray absorption spectra): 0.213+/-0.001nm, 0.213+/-0. 001 nm, 0.236+/-0.001 nm, 0.293+/-0.001 nm, 0.189+/-0.001 nm and 0. 242+/-0.001. Lyophilization of the LOX altered the binding distances but did not destroy the octahedral iron ligand sphere. For construction of a structural model of the iron ligand sphere the binding distances extracted from the X-ray spectra were assigned to specific amino acids (His-360, -365, -540, -544 and the C-terminal Ile-662) by molecular modelling using the crystal coordinates of the soybean LOX-1 and of a rabbit 15-LOX-inhibitor complex.
Kuban
R J
RJ
Institute of Biochemistry, University Clinics Charité, Humboldt University, Hessische Str. 3-4, D-10115 Berlin, Germany.
Wiesner
R
R
Rathman
J
J
Veldink
G
G
Nolting
H
H
Solé
V A
VA
Kühn
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011817:Rabbits; D016415:Sequence Alignment; D013025:Glycine max / Q000201:enzymology; D017356:Synchrotrons; D014965:X-Rays
D007501:Iron; D001093:Arachidonate 15-Lipoxygenase