THE IRON BINDING-SITES OF CHICKEN OVOTRANSFERRIN

Abstract

We have shown previously that the EXAFS spectrum of diferric chicken ovotransferrin (Fe2COT) can only be adequately simulated assuming a split first shell co-ordination [1]. EXAFS and XANES spectra of Fe2COT measured in solution and as a freeze-dried powder provide evidence for perturbation of the iron-binding sites on freeze-drying which involves the loss of one of the long (~2.04 A) first shell ligands (presumably water). Measurement of the XANES of the C-terminal monoferric COT and a C-terminal domain fragment suggests that the metal binding site remains largely unperturbed by the fragmentation process. The possibility of site interaction is briefly discussed.