Small-angle neutron scattering and dynamic light scattering studies of N- and C-terminal fragments of ovotransferrin.

In order to rationalize the physicochemical heterogeneities between the N- and C-lobes of ovotransferrin (OTf), we have analyzed the structural characteristics of the isolated fragments corresponding to the N- and C-terminal halves of OTf (OTf/2N and OTf/2C) with and without iron by means of small-angle neutron scattering (SANS) using the contrast variation method with solvents of various D2O/H2O mixtures, and dynamic light scattering (DLS) measurements. The analyses of the internal structural characteristics from SANS data revealed that the radius of gyration (Rg) for both fragments decreased to the same extent with iron binding, and the structural distortion of OTf/2C was smaller than that of OTf/2N, decreasing with iron uptake. The DLS studies showed that the change in the diffusion coefficient induced by iron binding to OTf/2C was greater than that to OTf/2N. It was inferred that the OTf/2C molecule tends to become more compact on the whole by iron binding as compared to the OTf/2N molecule.