Homology modeling and PAPS ligand (cofactor) binding study of bovine phenol sulfotransferase.

In order to understand the mechanisms of ligand binding and the interaction between the ligand and the bovine phenol sulfotransferase, (bSULT1A1, EC 2.8.2.1) a three-dimensional (3D) model of the bSULT1A1 is generated based on the crystal structure of the estrogen sulfotransferase (PDB code 1AQU) by using the InsightII/Homology module. With the aid of the molecular mechanics and molecular dynamics methods, the final refined model is obtained and is further assessed by Profile-3D and ProStat, which show that the refined model is reliable. With this model, a flexible docking study is performed and the results indicate that 3'-phosphoadenosine-5'- phosphosulfate (PAPS) is a more preferred ligand than coenzyme A (CoA), and that His108 forms hydrogen bond with PAPS, which is in good agreement with the experimental results. From these docking studies, we also suggest that Phe255, Phe24 and Tyr169 in bSULT1A1 are three important determinant residues in binding as they have strong van-der-Waals contacts with the ligand. The hydrogen-bonding interactions also play an important role for the stability of the complex. Our results may be helpful for further experimental investigations.