The distance between the two metal binding sites of human serum transferrin is calculated from measurements made of the paramagnetic broadening of the EPR spectrum of Cu2+ bound at the NH2-terminal (B) site from Fe3+ bound at the COOH-terminal (A) site. Complexes of monoferric(A)-monocupric(B) transferrin, monocupric(B) transferrin, and monogallium(A)-monocupric(B) transferrin were prepared under identical conditions. Computer simulation and direct measurement of the EPR spectra from these complexes demonstrate a paramagnetic broadening of 0.6 ± 0.1 G in the line width of the Cu2+ spectrum due to the paramagnetic Fe3+ bound at the other site. The distance between the two metal binding sites is calculated to be 41.6 ± 2.8 Å.
|Original language||English (US)|
|Number of pages||2|
|Journal||Journal of Biological Chemistry|
|State||Published - 1983|
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