Domain-specific binding of lactoferrin to plasminogen fragments

Aim.The aim of the study was to determine affinity of lactoferrin binding to Glu-plasminogen (Glu-Pg) and its fragments: kringles 1-3, 4 and 5 (K1-3, K4 and K5), and Val442-plasminogen (mini-Pg) in order to reveal plausible lactoferrin influence on the plasminogen/plasmin system.Methods.Glu-Pg, K1-3, K4, K5, and mini-Pg were tested for their ability to bind lactoferrin by ELISA using polyclonal antibodies to lactoferrin.Additionally, the complex formation between lactoferrin and K4, K5 and mini-Pg was confirmed by Far-western blotting technique.Results.We demonstrated lactoferrin binding to Glu-Pg, K1-3, K4, K5, and mini-Pg in a concentration-dependent manner.The calculated dissociation constants range from 2.09 × 10 -7 М to 7.29 × 10 -8 М, indicating a strong interaction between tested Glu-Pg/Glu-Pg domains and lactoferrin.Overall, lactoferrin exhibits the strongest affinity for K5, suggesting a potential preferential binding site within the whole plasminogen molecule.Conclusions.The obtained data support a previously reported potential inhibitory effect of lactoferrin on plasminogen/plasmin function.