Structure of mouse cytosolic sulfotransferase SULT2A8 provides insight into sulfonation of 7α-hydroxyl bile acids

Kai Wang,Yan-Chun Chan,Pui-Kin So,Xing Liu,Lu Feng,Wing-Tai Cheung,Susanna Sau-Tuen Lee,Shannon Wing-Ngor Au

doi:10.1016/j.jlr.2021.100074

Abstract

AbstractCytosolic sulfotransferases (SULTs) catalyze the transfer of a sulfonate group from the cofactor 3’-phosphoadenosine 5’-phosphosulfate to a hydroxyl (OH) containing substrate and play a critical role in the homeostasis of endogenous compounds, including hormones, neurotransmitters, and bile acids. In human, SULT2A1 sulfonates the 3-OH of bile acids; however, bile acid metabolism in mouse is dependent on a 7α-OH sulfonating SULT2A8 via unknown molecular mechanisms. In this study, the crystal structure of SULT2A8 in complex with adenosine 3’,5’-diphosphate and cholic acid was resolved at a resolution of 2.5 Å. Structural comparison with human SULT2A1 reveals different conformations of substrate binding loops. In addition, SULT2A8 possesses a unique substrate binding mode that positions the target 7α-OH of the bile acid close to the catalytic site. Furthermore, mapping of the critical residues by mutagenesis and enzyme activity assays further highlighted the importance of Lys44 and His48 for enzyme catalysis and Glu237 in loop 3 on substrate binding and stabilization. In addition, limited proteolysis and thermal shift assays suggested that the cofactor and substrates have protective roles in stabilizing SULT2A8 protein. Together, the findings unveil the structural basis of bile acid sulfonation targeting 7α-OH and shed light on the functional diversity of bile acid metabolism across species.

Highlights

IntroductionSulfonation involves the transfer of a sulfonate (SO3−) group from the universal cofactor 3’-phosphoadenosine-5’-phosphosulfate (PAPS) to a hydroxyl (OH) group of the substrate to generate a sulfonated product [18,19,20]
Supplementary key words bile acid metabolism protein structure homeostasis liver sulfotransferase mSULT2A8 X-ray crystallography 7-hydroxyl sulfonation
Full-length His-tagged SULT2A8 was cocrystallized with adenosine 3’ (PAP) or both PAP and Na sodium chenodeoxycholate (CDC); the crystals were only diffracted to resolutions of 3.6 and 7.9 Å, respectively

Summary

Introduction

Sulfonation involves the transfer of a sulfonate (SO3−) group from the universal cofactor 3’-phosphoadenosine-5’-phosphosulfate (PAPS) to a hydroxyl (OH) group of the substrate to generate a sulfonated product [18,19,20] Based on their amino acid sequence similarities, mammalian cytosolic SULTs are classified into six families (SULT1-SULT6), of which SULT1 and SULT2 are the largest and most important families for xenobiotic and endobiotic metabolism [21]. Previous investigation of the bile acid pool in mouse shows that 7-OH bile acidmonosulfates were the predominant forms, and their levels are higher in males than in females [35, 39, 40] This contradicts with the hepatic mRNA expression pattern of Sult2a1, which was exclusively detected in female mice [38], indicating that sulfonation of bile acids at 7-OH requires another SULT.

Methods

Results

Conclusion