Transferrin C subtypes in US blacks and whites.

Transferrin C is genetically heterogeneous. Isoelectric focusing in a pH gradient of 4.0-6.5 reveals two subtypes of transferrin C, TfC1 and TfC2, that differ slightly in their isoelectric point. The three transferrin bands seen in homozygotes (double bands for heterozygotes) probably represent different degrees of iron saturation. The most cathodal band consists of apotransferrin and the anodal band is fully saturated diferric transferrin. Family data are consistent with a codominant allelic mode of inheritance. The allele frequencies in US whites were 0.8 for TfC1 and 0.19 for TfC2; in US blacks the frequencies were 0.84 and 0.11, respectively. The concentrations of transferrin are probably the same for the three common phenotypes.