Sulfation is a major conjugation reaction for many endogenous sterols, catecholamines, bile acids and thyroid hormones as well as xenobiotics and therapeutic drugs. Structural changes in SULT2A1 elicited by the binding of PAPS, the obligate sulfonate donor, significantly regulate substrate selectivity. The binding of PAPS results in a structural rearrangement of loop3 (approx. 30 AA) that forms the outer surface of the PAPS and acceptor substrate binding pockets resulting a decrease of over 50% in the volume of the substrate binding pocket. Planar steroids such as dehydroepiandrosterone (DHEA) can bind in both the presence and absence of PAPS, whereas bulkier substrates such as raloxifene, can bind only if PAPS in not bound. Therefore, we hypothesize that interactions with PAPS in cells and tissues may be an important factor regulating substrate selectivity in the cytosolic SULT family. SULT2A1 is the only isoform for which well-resolved structures are available with and without PAP bound allowing for modeling of substrate binding in both these structural conformations of the enzyme. Also as observed within the SULT family, SULT2A1 is a dimer and shows substrate inhibition during the sulfation of increasing concentrations of DHEA. We have shown that monomeric SULT2A1 does not show substrate inhibition suggesting a role for subunit interactions in the regulation of SULT2A1 kinetics. Therefore, we propose to 1) investigate the role of structural remodeling on the substrate reactivity and kinetics of SULT2A1;2) analyze the role of dimerization on the kinetic properties of SULT2A1;3) characterize the role of PAPS- associated structural rearrangement in substrate recognition and kinetics for human SULT 1A1 and SULT1E1.

Public Health Relevance

Sulfotransferase (SULT) 2A1 is a major hepatic enzyme involved in the sulfation of endogenous sterols, bile acids as well as therapeutic drugs and many xenobiotics. SULT2A1 undergoes a structural rearrangement upon PAPS binding that regulates substrate selectivity as well as the kinetic properties of the enzyme. We propose to investigate the structural changes and interactions as well as the mechanistic features associated with substrate selectivity and kinetics in SULT2A1 both in vitro and in intact cultured cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM038953-25
Application #
8317669
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Okita, Richard T
Project Start
1987-07-01
Project End
2014-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
25
Fiscal Year
2012
Total Cost
$287,628
Indirect Cost
$52,008
Name
University of Alabama Birmingham
Department
Pharmacology
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
Tibbs, Zachary E; Falany, Charles N (2016) An engineered heterodimeric model to investigate SULT1B1 dependence on intersubunit communication. Biochem Pharmacol 115:123-33
Tibbs, Zachary E; Rohn-Glowacki, Katie Jo; Crittenden, Frank et al. (2015) Structural plasticity in the human cytosolic sulfotransferase dimer and its role in substrate selectivity and catalysis. Drug Metab Pharmacokinet 30:3-20
Wang, Ting; Cook, Ian; Falany, Charles N et al. (2014) Paradigms of sulfotransferase catalysis: the mechanism of SULT2A1. J Biol Chem 289:26474-80
Rohn-Glowacki, Katie Jo; Falany, Charles N (2014) The potent inhibition of human cytosolic sulfotransferase 1A1 by 17α-ethinylestradiol is due to interactions with isoleucine 89 on loop 1. Horm Mol Biol Clin Investig 20:81-90
Duniec-Dmuchowski, Zofia; Rondini, Elizabeth A; Tibbs, Zachary E et al. (2014) Expression of the orphan cytosolic sulfotransferase SULT1C3 in human intestine: characterization of the transcript variant and implications for function. Drug Metab Dispos 42:352-60
Cook, Ian; Wang, Ting; Almo, Steven C et al. (2013) The gate that governs sulfotransferase selectivity. Biochemistry 52:415-24
Runge-Morris, Melissa; Kocarek, Thomas A; Falany, Charles N (2013) Regulation of the cytosolic sulfotransferases by nuclear receptors. Drug Metab Rev 45:15-33
Leyh, Thomas S; Cook, Ian; Wang, Ting (2013) Structure, dynamics and selectivity in the sulfotransferase family. Drug Metab Rev 45:423-30
Cook, Ian; Wang, Ting; Falany, Charles N et al. (2013) High accuracy in silico sulfotransferase models. J Biol Chem 288:34494-501
Falany, Charles N; Rohn-Glowacki, Katie Jo (2013) SULT2B1: unique properties and characteristics of a hydroxysteroid sulfotransferase family. Drug Metab Rev 45:388-400

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