The Fe-heme structure of met-indoleamine 2,3-dioxygenase-2 determined by X-ray absorption fine structure
Jade B Aitken1, Christopher J D Austin2, Nicholas H Hunt3
1School of Chemistry, The University of Sydney, NSW 2006, Australia; Australian Synchrotron, Clayton, Victoria 3168, Australia; Institute of Materials Structure Science, KEK, Tsukuba, Ibaraki 305-0801, Japan.
Abstract:
Multiple-scattering (MS) analysis of EXAFS data on met-indoleamine 2,3-dioxygenase-2 (IDO2) and analysis of XANES have provided the first direct structural information about the axial donor ligands of the iron center for this recently discovered protein. At 10K, it exists in a low-spin bis(His) form with Fe-Np(av)=1.97Å, the Fe-NIm bond lengths of 2.11Å and 2.05Å, which is in equilibrium with a high-spin form at room temperature. The bond distances in the low-spin form are consistent with other low-spin hemeproteins, as is the XANES spectrum, which is closer to that of the low-spin met-Lb than that of the high-spin met-Mb. The potential physiological role of this spin equilibrium is discussed.
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