A comparative binding mechanism between human serum albumin and alpha-1-acid glycoprotein with corilagin: biophysical and computational approach

作者：Yeggoni Daniel Pushparaju; Rachamallu Aparna; Subramanyam Rajagopal

来源：RSC Advances, 2016, 6(46): 40225-40237.

DOI：10.1039/c6ra06837e

The binding of corilagin with plasma serum proteins like human serum albumin (HSA) and alpha-1-acid glycoprotein (AGP) was investigated under physiological conditions. To understand the pharmacological importance of the corilagin molecule, anti-inflammatory activity on mouse macrophages (RAW 264.7) cell lines was studied. This study reveals that corilagin caused an increase in inhibition growth of inflamed macrophages in concentration-dependent manner with an IC50 value of 66 mu M. Further, intrinsic fluorescence of HSA and AGP was quenched upon titration of corilagin, and the binding constants obtained from fluorescence emission was found to be K-corilagin 4.2 +/- 0.02 x 10(5) M-1 which corresponds to the free energy of -7.6 kcal M-1 at 25 degrees C for a HSA-corilagin complex. Interestingly, corilagin showed binding with AGP, an acute phase protein, and the binding constant was found to be K-corilagin = 1.5 +/- 0.01 x 10(4) M-1 and its free energy was -5.6 kcal M-1 at 25 degrees C. Further, the average binding distance, r, between the donor (HSA) and acceptor (corilagin) was calculated and found to be 1.32 nm according to Forster's theory of non-radiation energy transfer. Later, circular dichroism studies emphasized that there are marginal changes in secondary structural conformation of HSA in the presence of corilagin. Corilagin is specifically bound to site I of HSA which was proved by site specific marker, phenylbutazone. Furthermore, the binding details between corilagin and HSA revealed that corilagin was bound to subdomain IIA through multiple interactions like hydrogen bonding and hydrophobic effects. Molecular dynamic studies (MD) also suggest that binding is very precise to site I (IIA domain) on HSA. Also, MD studies showed that HSA-corilagin complex reaches equilibration state at around 4 ns, which proves that the HSA-corilagin complex is stable in nature, hence the experimental and computational results are in agreement. Thus, examining the interaction mechanism of corilagin with plasma proteins may play a critical role in developing corilagin inspired drugs.

• 出版日期2016