A New Variant of Human Transferrin in a Venezuelan Family

THE most prolific of the hereditary variations among the human serum proteins is that of the iron-transport protein transferrin. The initial demonstration of genetically determined transferrin heterogeneity 1 has been followed by numerous reports of additional variants, until at the present time thirteen transferrins have been described: B 0 (ref. 2), B 0–1 (ref. 3), B 1 (ref. 4), B 2 (ref. 5), B 3 (ref. 6), C, D 0 (ref. 2), D 4 (ref. 7), D Montreal (ref. 8), D Chi (ref. 6), D 1 (ref 9), D 2 (ref. 4), and D 3 (ref. 2). Each of the molecular species of transferrin has been identified by its characteristic mobility in starch-gel electrophoresis. Transferrin C is common in all populations; variants of more rapid mobility than transferrin C have been named B, and slower-moving variants have been labelled D. Where convenient, subscripts have been chosen to define the relative electrophoretic mobilities of variants within the fast- and slow-moving categories. In certain cases, particular transferrins appear to be restricted to specific populations; thus, transferrin B 0–1 occurs in 8 per cent of Navajo Indians, B 2 in 1 per cent of Caucasians, D Chi in 6 per cent of Chinese, and D 1 in 10 per cent of American Negroes.