Human milk lactoferrin binds ATP and dissociates into monomers

The physiological role of lactoferrin (LF) is still unclear, but it has bee n suggested to be responsible for primary defence against microbial infecti ons. Many different unique functions have been attributed to LF, including DNA and RNA binding, and transport into the nucleus, where LF binds to spec ific DNA sequences and activates transcription. Here we present evidence th at in addition to the above (and below) mentioned functions LF binds ATP wi th a stoichiometry of 1 mole of nucleotide per mole of the protein and a K- d=0.3 mM. The ATP-binding site is localized in the C-terminal domain of LF, in contrast to the antibacterial and polyanion-binding sites, which are lo cated in the N-terminal domain. Binding of ATP by LF leads to dissociation of its oligomeric forms and to a change of the protein's interaction with p olysaccharides, DNA and proteins.