Multiple Mutations Modulate the Molecular Interaction between Steroid Sulfatases and Formylglycine Generating Enzyme: A Computational Study

Abstract Major naturally occurring estrogens are estrone, estradiol and estratriol. Sulfates of naturally occurring estrogen act as reservoirs of potent estrogen and are important at different stages of life among which estrone sulfate is found to be circulating ten times more than estradiol specifically in postmenopausal women. Sulfate esters of estrogen are hydrolyzed by steroid sulfatases (STS) only after it is activated by the enzyme formylglycine generating enzyme (FGE), which is encoded by the gene Sulfatase modifying factor 1 (SUMF1). SUMF1 mutation or dysfunction leads to several pathological consequences. Now identified as a prognostic marker, elevated expression and activity of STS has been observed in several human malignancies and has led to the identification of its inhibitors. Thirteen different sulfatases have been identified in human, all of which are activated by single enzyme FGE. Therefore, we asked the question, does FGE interacts with STS in a unique manner that differs from other group of sulfatases. To address our question, protein-protein molecular docking studies were performed using two docking softwares PyDock and HDOCK with special emphasis on STS and FGE interaction. The present study for the first time reports the basics of molecular interaction/ binding studies of the four major sulfatase groups of enzymes with FGE and reveals the amino acid residues involved for specific sulfatase groups. Interestingly, interaction of STS and FGE was found to be the most stable with highest binding energy and docking score with specific amino acid residues involved. Single or multiple site-directed mutagenesis provides invaluable tool for protein engineering that may be used to inhibit or enhance the function of a protein. To understand the effect of site-specific mutations in STS on its interaction with FGE, we performed mutational studies. Removal of specific amino acid residues significantly affected the interaction of STS with FGE increasing the electrostatic energy and reducing Van der Waal energy drastically. These findings suggest that targeting these specific amino acid residues can inhibit the interaction of FGE with STS leading to reduced activity of STS that in turn may inhibit the production of estradiol thereby reducing cancer progression.