Elucidation on the Interaction Between Transferrin and Tetrachlorobisphenol A Based on Multispectroscopic Analysis, Molecular Docking Technique, and Conformational Studies.

Tetrachlorobisphenol A (TCBPA) is a kind of fire retardant extensively used in our life, but it can accumulate in organisms and potentially have toxic effects. Transferrin (TF) is a glycoprotein predominantly present in the blood plasma, serving as an essential mediator for the transportation of iron and other small molecules. In our study, various techniques including multi-spectroscopic and molecular docking were employed to examine the interaction between TCBPA and TF. The TF-TCBPA complex was formed with the binding constant (K_a) in 2.181 ± 0.035 × 10⁴ M^-1 at 298 K. ΔH and ΔS were all negative, which means dominant driving forces were van der Waals forces and H-bonds. The secondary structure of TF was changed by TCBPA, resulting in a decline in the α-helix structure, and a corresponding increase in the β-sheet structure. The molecular docking revealed that TCBPA was positioned within a pocket of TF, and it engaged in interactions with some amino acid residues through different forces. Importantly, the interaction between Tyr426/Asp392/His585 and TCBPA implies that TCBPA potentially interferes with the transportation of iron ions in vivo. All of above results indicated the adverse effects of TCBPA on the TF structure and activity should be more attention.