The C2 variant of human serum transferrin retains the iron binding properties of the native protein

The tryptic digests of blood samples obtained from transferrin C1 and C2 (TfC1 and TfC2 hereafter) genotypes were analysed by Liquid Chromatography coupled to Electrospray Mass Spectrometry (LC/ESI-MS/MS). The analytical results confirmed the single base change in exon 15 of the Tf gene. The solution behaviour and the iron binding properties of the two Tf variants were studied by UV-visible spectrophotometry and by circular dichroism. It appears that TfC2 globally manifests the same spectral features as the native protein. The local conformation of the two iron binding sites is conserved in the two Tf variants as evidenced by the visible absorption and CD spectra. Also, the iron binding capacities and their pH-dependent profiles are essentially the same. Overall, our investigation points out that the single amino acid substitution in TfC2 (Pro570Ser) does not affect the general conformation of the protein nor the local structure of the iron binding sites. The implications of these results for the etiopathogenesis of Alzheimer's disease are discussed.