The Mechanism of Action of Lactoferrin - Nucleoside Diphosphate Kinase Complex in Combating Biofilm Formation

Abstract

Background: The ESKAPE group of pathogens which comprise of multidrug resistant bacteria, namely Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species are the cause of deadly nosocomial infections all over the world. While these pathogens have developed robust strategies to resist most antibiotics, their ability to form biofilms is one of their most combative properties. Hence there is an urgent need to discover new antibacterial agents which could prevent or destroy the biofilms made by these bacteria. Though it has been established that lactoferrin (LF), a potent iron binding antibacterial, antifungal, and antiviral protein displays anti-biofilm properties, its mechanisms of action, in addition to its iron chelation property, still remains unclear. Objective: The binding and inhibition studies of LF with the enzyme Nucleoside diphosphate Kinase (NDK) and its elastase cleaved truncated 12 kDa fragment (12-NDK). Methods: The characterization studies of NDK and 12-NDK using florescence spectroscopy, dynamic light scattering, size exclusion chromatography and ADP-glo Kinase Assay. Inhibition studies of LF-NDK using ADP-glo kinase assay, Surface Plasmon Resonance and Biofilm inhibition studies. Results: NDK and 12-NDK were cloned, expressed and purified from Acinetobacter baumannii and Pseudomonas aeruginosa. The characterization studies revealed NDK and 12-NDK from both species are stable and functional. The inhibition studies of LF-NDK revealed stable binding and inhibition of kinase activity by LF. Conclusion: The binding and inhibition studies have shown that while LF binds with both the NDK and their truncated forms, it tends to have a higher binding affinity with the truncated 12 kDa fragments, resulting in their decreased kinase activity. This study essentially gives a new direction to the field of inhibition of biofilm formation, as it proves that LF has a novel mechanism of action in other than iron sequestration.