Conformations of denatured and renatured ovotransferrin

Abstract

Conformational properties of native, denatured, and renatured ovotransferrin were studied. The samples were denatured either in 7.2 M urea or in acidic (pH 3.0) conditions for periods up to a few hours. Combined data from quasielastic light scattering and transient electric birefringence were used to estimate the molecular dimensions under the various conditions. The native ovotransferrin is best described as a prolate ellipsoid with a major axis a = 68 A and a minor axis b = 21 A. Such an ellipsoidal shape is consistent with a globular particle where the solvation factor is approximately 0.28 mg/mg of solute. The urea-denatured sample was more expanded and more globular than the native sample. This observation was supported by a decrease in helical content, which was shown using circular dichroism data. Complete recovery of conformation and capacity to form a colored complex with Fe3+ seemed to occur with the simple dilution of urea or by adjustment of the low pH sample to pH 7.3.