Abstract
Lactoferrin is a heme-binding multifunctional glycoprotein known for iron transportation in the blood and also contributes to innate immunity. In this study, the interaction of theaflavin monogallate, a polyphenolic component of black tea, with camel milk lactoferrin was studied using various biophysical and computational techniques. Fluorescence quenching at different temperatures suggests that theaflavin monogallate interacted with lactoferrin by forming a non-fluorescent complex, i.e., static quenching. Theaflavin monogallate shows a significant affinity towards lactoferrin with a binding constant of ∼104–105 M−1 at different temperatures. ANS binding shows that the binding of polyphenol resulted in the burial of hydrophobic domains of lactoferrin. Moreover, thermodynamic parameters (ΔH, ΔS and ΔG) suggested that the interaction between protein and polyphenol was entropically favored and spontaneous. Circular dichroism confirmed there was no alteration in the secondary structure of lactoferrin. The energy transfer efficiency (FRET) from lactoferrin to theaflavin was found to be approximately 50%, with a distance between protein and polyphenol of 2.44 nm. Molecular docking shows that the binding energy of lactoferrin–theaflavin monogallate interaction was −9.7 kcal mol−1. Theaflavin monogallate was bound at the central cavity of lactoferrin and formed hydrogen bonds with Gln89, Tyr192, Lys301, Ser303, Gln87, and Val250 of lactoferrin. Other residues, such as Tyr82, Tyr92, and Tyr192, were involved in hydrophobic interactions. The calculation of various molecular dynamics simulations parameters indicated the formation of a stable complex between protein and polyphenol. This study delineates the binding mechanism of polyphenol with milk protein and could be helpful in milk formulations and play a key role in the food industry.
Highlights
A simple polypeptide chain of lactoferrin is folded to form two symmetrical lobes
The results indicate that binding of thea avin monogallate competed for the binding site of ANS
The ndings of this study provide detailed insights into the interaction between thea avin monogallate and lactoferrin
Summary
A simple polypeptide chain of lactoferrin is folded to form two symmetrical lobes These two lobes (N and C) are highly homologous of approximately 33–41%.8. Thea avins are a class of polyphenols and is a major component of black tea They are regarded as ‘golden molecules’ owing to their therapeutic attributions.[17] They have been shown to have various physiological actions, including antioxidant,[18] anticancer,[19] anti-atherosclerotic,[20] anti-in ammatory,[21] antiviral,[22,23] anti-periodontitis[24] and the inhibition of osteoporosis.[25] these compounds have been shown to possess human health bene ts including glucose-lowering[26] anti-obesity[27] as a prevention of lifestyle-related diseases. Several biophysical and computational tools were performed to reveal the conformational changes and mechanism of binding between protein– polyphenols complex
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