Transferrins structural aspects

A potentially confusing aspect of transferrin structure and function is that, prior to determination of the lactoferrin and transferrin structures, the N- and C-terminal halves of each molecule were often referred to as N- and C-domains. Given the clear subdivisions apparent in Fig. 4, however, the commonly accepted definition of protein domains (separately folded units see Ref. 83), and the functional importance of these units, it seems preferable to think of the transferrins as proteins comprising two lobes, but four domains. 

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