Biochemical and spectroscopic studies of human melanotransferrin (MTf): electron-paramagnetic resonance evidence for a difference between the iron-binding site of MTf and other transferrins
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Authors
Farnaud, SébastienAmini, Maryam
Rapisarda, Chiara
Cammack, Richard
Bui, Tam
Drake, Alex F.
Evans, Robert W.
Rahmanto, Yohan Suryo
Richardson, Des R.
Issue Date
2008-01Subjects
melanotransferrintransferrin
iron
electron-paramagnetic resonance spectroscopy
circular dichroism (CD)
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Show full item recordAbstract
Melanotransferrin (MTf) is a member of the transferrin (Tf) family of iron (Fe)-binding proteins that was first identified as a cell-surface marker of melanoma. Although MTf has a high-affinity Fe-binding site that is practically identical to that of serum Tf, the protein does not play an essential role in Fe homeostasis and its precise molecular function remains unclear. A Zn(II)-binding motif, distinct from the Fe-binding site, has been proposed in human MTf based on computer modelling studies. However, little is known concerning the interaction of its proposed binding site(s) with metals and the consequences in terms of MTf conformation. For the first time, biochemical and spectroscopic techniques have been used in this study to characterise metal ion-binding to recombinant MTf. Initially, the binding of Fe to MTf was examined using 6 M urea gel electrophoresis. Although four different iron-loaded forms were observed with serum Tf, only two forms were found with MTf, the apo-form and the N-monoferric holo-protein, suggesting a single high-affinity site. The presence of a single Fe(III)-binding site was also supported by EPR results which indicated that the Fe(III)-binding characteristics of MTf were unique, but somewhat comparable to the N-lobes of human serum Tf and chicken ovo-Tf. Circular dichroism (CD) analysis indicated that, as for Tf, no changes in secondary structure could be observed upon Fe(III)-binding. The ability of MTf to bind Zn(II) was also investigated using CD which demonstrated that the single high-affinity Fe-binding site was distinct from a potential Zn(II)-binding site.Citation
Farnaud, S., Amini, M., Rapisarda, C., Cammack, R., Bui, T., Drake., A., Evans, R., Rahmanto, Y., Richardson, D. (2008) 'Biochemical and spectroscopic studies of human melanotransferrin (MTf): Electron-paramagnetic resonance evidence for a difference between the iron-binding site of MTf and other transferrins' The International Journal of Biochemistry & Cell Biology 40 (12):2739Publisher
ElsevierAdditional Links
http://linkinghub.elsevier.com/retrieve/pii/S1357272508003038Type
ArticleLanguage
enISSN
1357-2725ae974a485f413a2113503eed53cd6c53
10.1016/j.biocel.2008.07.003