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3'-Phosphoadenosine 5'-phosphosulfate allosterically regulates sulfotransferase turnover.

ABSTRACT: Human cytosolic sulfotransferases (SULTs) regulate the activities of thousands of small molecules-metabolites, drugs, and other xenobiotics-via the transfer of the sulfuryl moiety (-SO3) from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the hydroxyls and primary amines of acceptors. SULT1A1 is the most abundant SULT in liver and has the broadest substrate spectrum of any SULT. Here we present the discovery of a new form of SULT1A1 allosteric regulation that modulates the catalytic efficiency of the enzyme over a 130-fold dynamic range. The molecular basis of the regulation is explored in detail and is shown to be rooted in an energetic coupling between the active-site caps of adjacent subunits in the SULT1A1 dimer. The first nucleotide to bind causes closure of the cap to which it is bound and at the same time stabilizes the cap in the adjacent subunit in the open position. Binding of the second nucleotide causes both caps to open. Cap closure sterically controls active-site access of the nucleotide and acceptor; consequently, the structural changes in the cap that occur as a function of nucleotide occupancy lead to changes in the substrate affinities and turnover of the enzyme. PAPS levels in tissues from a variety of organs suggest that the catalytic efficiency of the enzyme varies across tissues over the full 130-fold range and that efficiency is greatest in those tissues that experience the greatest xenobiotic "load".

SUBMITTER: Wang T

PROVIDER: S-EPMC4230322 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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3'-Phosphoadenosine 5'-phosphosulfate allosterically regulates sulfotransferase turnover.

Wang Ting T Cook Ian I Leyh Thomas S TS

Biochemistry 20141027 44

Human cytosolic sulfotransferases (SULTs) regulate the activities of thousands of small molecules-metabolites, drugs, and other xenobiotics-via the transfer of the sulfuryl moiety (-SO3) from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the hydroxyls and primary amines of acceptors. SULT1A1 is the most abundant SULT in liver and has the broadest substrate spectrum of any SULT. Here we present the discovery of a new form of SULT1A1 allosteric regulation that modulates the catalytic efficiency ...[more]

PMID: 25314023

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Project description:The cytosolic sulfotransferases (SULTs) catalyze the sulfate conjugation of nucleophilic substrates, and the cofactor for sulfonation, 3'-phosphoadenosine-5'-phosphosulfate (PAPS), is biosynthesized from sulfate and ATP. The phenotype of male knockout mice for the NaS1 sodium sulfate cotransporter includes hyposulfatemia and increased hepatic expression of mouse cytoplasmic sulfotransferase Sult2a and Sult3a1. Here we report that in 8-week-old female NaS1-null mice, hepatic Sult2a1 mRNA levels were ∼51-fold higher than they were in a wild-type liver but expression of no other Sult was affected. To address whether hyposulfatemia-inducible Sult2a1 expression might be due to reduced PAPS levels, we stably knocked down PAPS synthases 1 and 2 in HepG2 cells (shPAPSS1/2 cells). When a reporter plasmid containing at least 233 nucleotides (nt) of Sult2a1 5'-flanking sequence was transfected into shPAPSS1/2 cells, reporter activity was significantly increased relative to the activity that was seen for reporters containing 179 or fewer nucleotides. Mutation of an IR0 (inverted repeat of AGGTCA, with 0 intervening bases) nuclear receptor motif at nt -191 to 180 significantly attenuated the PAPSS1/2 knockdown-mediated increase. PAPSS1/2 knockdown significantly activated farnesoid X receptor (FXR), retinoid-related orphan receptor, and pregnane X receptor responsive reporters, and treatment with the FXR agonist GW4064 [3-(2,6-dichlorophenyl)-4-(3'-carboxy-2-chlorostilben-4-yl)oxymethyl-5-isopropylisoxazole] increased Sult2a1 promoter activity when the IR0 was intact. Transfection of shPAPSS1/2 cells with FXR small interfering RNA (siRNA) significantly reduced the Sult2a1 promoter activity. The impact of PAPSS1/2 knockdown on Sult2a1 promoter activity was recapitulated by knocking down endogenous SULT2A1 expression in HepG2 cells. We propose that hyposulfatemia leads to hepatic PAPS depletion, which causes loss of SULT2A1 activity and results in accumulation of nonsulfated bile acids and FXR activation.

Dataset Information

3'-Phosphoadenosine 5'-phosphosulfate allosterically regulates sulfotransferase turnover.

Publications

3'-Phosphoadenosine 5'-phosphosulfate allosterically regulates sulfotransferase turnover.

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