Conformational Changes of Human Serum Albumin and Bovine Serum Albumin Induced by 1-Naphthol

KeyWord:1-naphthol  fluorescence quenching  conformational change  human serum albumin  bovine serum albumin

Abstract:

      The typical polycyclic aromatic hydrocarbons(PAHs) metabolite 1-napthol(1-OHNap) is ubiquitously existing in smoker¥“s blood.It¥“s worth paying attention to the binding interaction between the most abundant transport albumin and 1-OHNap at molecular level.The crystal structures of human serum albumin(HSA) and bovine serum albumin(BSA) are different.There are still many studies using BSA as model protein to investigate the ligand-protein interactions.The main aim here was to explore the differences of binding mechanism between carrier protein HSA and BSA with 1-OHNap under the simulated physiological condition.The binding interactions between 1-OHNap and two serum albumin were investigated by steady-state fluorescence spectra,synchronous fluorescence spectra,CD spectra,fluorescence resonance energy transfer technique and molecular docking method.The fluorescence quenching experimental results showed that 1-OHNap interacted with both tryptophan(Trp) and tyrosine(Tyr) residues in HSA and BSA.The position and strength of characteristic fluorescence spectra of both HSA and BSA had been changed differently after binding with 1-OHNap.Meanwhile,the synchronous fluorescence spectra experimental results suggested that the binding interactions with 1-OHNap changed the polarity of the microenvironment of binding sites around the fluorophore in HSA.Besides,the binding interaction with 1-OHNap increased the polarity of the microenvironment around Trp residues in BSA.Then,the CD spectra were used to obtain the changes in the secondary structure of HSA and BSA after binding with 1-OHNap.The CD spectra experimental results indicated that the binding interaction with 1-OHNap caused the slight unfolding of polypeptide chains in both HSA and BSA.The amplitudes of the ¦Á-helical ratios of both HSA and BSA decreased after binding with 1-OHNap.Furthermore,the decreasing amplitude of the ¦Á-helical ratio of BSA was lower than that of HSA.The binding constants of 1-OHNap with HSA and BSA were calculated by using double logarithmic equation fitting.The binding constants of 1-OHNap with HSA and BSA were 1.49¡Á104 L/mol and 8.76¡Á103 L/mol,respectively.The molecular docking method was used to obtain the optimal binding sites of 1-OHNap in HSA and BSA,which were located at subdomain ¢òA and ¢ñB,respectively.Then the distances between 1-OHNap at the optimal binding site and Trp214 in HSA,Trp 134 and Trp213 in BSA were obtained by Pymol software.The energy transfer efficiencies and apparent distances between the receptor 1-OHNap and the donar Trp residues in HSA and BSA were calculated by using the fluorescence resonance energy transfer technique.The apparent distances from 1-OHNap to Trp residues in HSA and BSA were calculated to be 1.53 nm and 1.42 nm,respectively.The above experimental results confirmed that the conformational changes of HSA and BSA after binding with 1-OHNap were significantly different.