Human milk lactoferrin binds two DNA molecules with different affinities

Evidence is presented that lactoferrin (LF), an Fe3+-binding glycoprotein, possesses two DNA-binding sites with different affinities for specific olig onucleotides (ODNs) (K-d1 = 8 nM; K-d2 similar to 0.1 mM), The high affinit y site became labeled after incubation with affinity probes for DNA-binding sites; like the antibacterial and polyanion-binding sites, this site was s hown to be located in the N-terminal domain of LF. Interaction of heparin w ith the polyanion-binding site inhibits the binding of ODNs to both sites. These data suggest that the DNA-binding sites of LF coincide or overlap wit h the known polyanion and antimicrobial domains of the protein. (C) 1999 Fe deration of European Biochemical Societies.