Crystal Structure of the Human Estrogen Sulfotransferase-PAPS Complex

Fuda

Journal of Biological Chemistry

et al. 2003

Self Cite

The gene for human hydroxysteroid sulfotransferase (SULT2B1) encodes two peptides, SULT2B1a and SULT2B1b, that differ only at their amino termini. SULT2B1b has a predilection for cholesterol but is also capable of sulfonating pregnenolone, whereas SULT2B1a preferentially sulfonates pregnenolone and only minimally sulfonates cholesterol. We have determined the crystal structure of SULT2B1a and SULT2B1b bound to the substrate donor product 3 -phosphoadenosine 5 -phosphate at 2.9 and 2.4 Å, respectively, as well as SULT2B1b in the presence of the acceptor substrate pregnenolone at 2.3 Å. These structures reveal a different catalytic binding orientation for the substrate from a previously determined structure of hydroxysteroid sulfotransferase (SULT2A1) binding dehydroepiandrosterone. In addition, the amino-terminal helix comprising residues Asp 19 to Lys 26 , which determines the specificity difference between the SULT2B1 isoforms, becomes ordered upon pregnenolone binding, covering the substrate binding pocket.

Section: Discussionmentioning

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Crystal Structure of Human Cholesterol Sulfotransferase (SULT2B1b) in the Presence of Pregnenolone and 3′-Phosphoadenosine 5′-Phosphate

Fuda

Journal of Biological Chemistry

et al. 2003

Self Cite

Journal of Biological Chemistry

“…SULT crystal structures have been determined for mouse estrogen SULT1E1 complexed with PAP/E2 (Protein Data Bank (PDB) codes in parentheses) (1AQU), PAP (1AQY), or PAP/vanadate (1BO6) (14); human estrogen SULT1E1 complexed with PAPS (1HY3) (15); human dopamine SULT1A3 complexed with SO 4 2Ϫ (1CJM) (16) or PAP (10); human hydroxysteroid SULT2A3 complexed with PAP (1EFH) (17); the SULT domain of heparin sulfate-N-deacetylase complexed with PAP (1NST) (18); and human dehydroepiandrosterone sulfotransferase (DEA-SULT) complexed with substrate (1J99) (19). All of these structures incorporate a common PAPS binding region and a variable substrate binding region.…”

mentioning

confidence: 99%

Structure of a Human Carcinogen-converting Enzyme, SULT1A1

Gamage

Duggleby

Barnett

et al. 2003

148

Sulfonation catalyzed by sulfotransferase enzymes plays an important role in chemical defense mechanisms against various xenobiotics but also bioactivates carcinogens. A major human sulfotransferase, SULT1A1, metabolizes and/or bioactivates many endogenous compounds and is implicated in a range of cancers because of its ability to modify diverse promutagen and procarcinogen xenobiotics. The crystal structure of human SULT1A1 reported here is the first sulfotransferase structure complexed with a xenobiotic substrate. An unexpected finding is that the enzyme accommodates not one but two molecules of the xenobiotic model substrate p-nitrophenol in the active site. This result is supported by kinetic data for SULT1A1 that show substrate inhibition for this small xenobiotic. The extended active site of SULT1A1 is consistent with binding of diiodothyronine but cannot easily accommodate ␤-estradiol, although both are known substrates. This observation, together with evidence for a disorder-order transition in SULT1A1, suggests that the active site is flexible and can adapt its architecture to accept diverse hydrophobic substrates with varying sizes, shapes and flexibility. Thus the crystal structure of SULT1A1 provides the molecular basis for substrate inhibition and reveals the first clues as to how the enzyme sulfonates a wide variety of lipophilic compounds.Sulfonation is a widely distributed biological reaction catalyzed by members of the supergene family of enzymes called sulfotransferases (SULTs).1 SULTs utilize the sulfonate donor 3Ј-phosphoadenosine 5Ј-phosphosulfate (PAPS) to catalyze sulfonation, yielding PAP as the desulfonated product of the reaction. These enzymes modify the biological activities of a diverse range of compounds including neurotransmitters, hormones, and drugs. The reaction aids excretion of foreign chemicals but, in some cases, causes bioactivation of carcinogens and mutagens (1-3). SULTs are the focus of intense research in the fields of cancer, drug metabolism, and pharmacogenetics because genetic variation, particularly in isoenzyme SULT1A1, may predispose to lung cancers (4), protect against colorectal cancers (5), and affect the age of onset in breast cancer (6).To date, five distinct mammalian gene families for cytosolic SULTs (SULTs 1-5) have been identified (7), although SULT3 and SULT5 have not been found in humans (8). The most extensive group of the human cytosolic SULTs is the SULT1 family, which includes SULTs 1A1, 1A2, 1A3, 1B1, 1C1, 1C2, and 1E1. Each SULT has distinct substrate preferences but may also exhibit broad and overlapping substrate specificity to span the diversity of chemicals requiring sulfonation. For example, SULT1A3 catalyzes dopamine sulfonation but also accepts p-nitrophenol (pNP) with lower affinity (9, 10). SULT1A1, which shares 93% identity with SULT1A3, also sulfonates dopamine and pNP but with the reverse preference, and in addition it can sulfonate a wide range of hydrophobic molecules (Fig. 1) including xenobiotics and endogenous substrates 3,3Ј-diio...

Encyclopedia of Drug Metabolism and Interactions

Sulfotransferases

Ma¹,

Schrag²

2012

The sulfotransferases (SULTs) are a family of phase II enzymes that catalyze the transfer of a sulfonate group (‐SO 3− ) from the cofactor 3′‐phosphoadenosine‐5′‐phosphosulfate (PAPS) to an acceptor molecule or substrate. Since these enzymes can conjugate with a wide variety of xenobiotics and endogenous substrates, they function not only as drug‐metabolizing enzymes but also modulators of physiological activities through conjugations of endogenous molecules such as steroids, catecholamines, and thyroid hormones. This chapter aims to provide drug metabolism scientists with an introductory overview on various aspects of SULTs along with challenges and complications associated with SULT‐mediated biotransformations, particularly encountered during the drug discovery and development process. In recent years, commercially available hepatocyte preparations and recombinant SULT enzymes facilitate the determination of SULT involvement for compounds of interest. However, significant challenges do remain. For example, when conducting reaction‐phenotyping experiments for SULT‐catalyzed conjugations, there is currently a lack of well‐characterized isoform‐specific probe substrates and inhibitors, in addition to a lack of well‐established in vitro incubation conditions. Kinetic experiments, too, often require careful interpretation, as profound substrate inhibition is rather common for sulfation reactions. From the toxicology stand‐point, sulfation may pose liability concerns due to the potential formation of reactive electron‐deficient metabolite species. It is recommended that investigators should take the time to explore and understand the properties of SULT‐mediated conjugations and their implications.