INTERACTION OF HUMAN-MILK LACTOFERRIN WITH ATP

Human lactoferrin exhibits many unique properties. It is known as one of the most important factors that provide nonspecific defense of cell s against bacteria, viruses, and carcinogenesis, as well as an importa nt component of a specific system responsible for the passive immunity of newborns. As a compound with extremely broad spectrum of functions many of which were not elucidated so far, lactoferrin is intensely st udied. In this study we obtained electrophoretically and immunological ly homogenous preparations of lactoferrin from human milk. Using vario us methods, we were the first to show that the fraction of lactoferrin , which displays an increased affinity for Sepharose Blue, forms compl exes with ATP with a stoichiometry of 1 mole ATP per mole protein. It is shown that the ATP-binding site is located in the C-terminal domain of the lactoferrin molecule. The binding of ATP results in the dissoc iation of tetrameric forms of the protein and a change in the mode of interaction of lactoferrin with polysaccharides and other proteins. Th e data may be used in analysis of the possible reasons for multifuncti onal properties of lactoferrin and possible ways of regulation of its functions.