Lack of substrate inhibition in a monomeric form of human cytosolic SULT2A1

Ian T. Cook, Thomas S. Leyh, Susan A. Kadlubar, Charles N. Falany

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Mammalian cytosolic sulfotransferases (SULTs) frequently show substrate inhibition during the sulfation of increasing concentrations of substrates. SULT2A1, a major human liver isoform responsible for the conjugation of hydroxysteroids, bile acids and aliphatic hydroxyl groups in drugs and xenobiotics, is a homodimer and displays substrate inhibition during the conjugation of dehydroepiandrosterone (DHEA). Maltose binding protein (MBP)-SULT2A1 fusion protein, produced as an intermediate step in the purification of the SULT2A1 homodimer, elutes during size exclusion chromatography as a monomer. The initial-rate parameters (Km and Vmax) of the monomer (MBP-SULT2A1) and native SULT2A1 dimer for DHEA sulfation are extremely similar; however, the monomer is not inhibited by DHEA. Intrinsic fluorescence studies show that two DHEA molecules bind each SULT2A1 subunit, one in the catalytic site and one in an apparent allosteric site. Lack of dimerization in the MBPSULT2A1 fusion protein decreased the Kd for binding of DHEA at the allosteric site. These results suggest that formation of the homodimer is associated with structural rearrangements leading to increased DHEA binding at an allosteric site that is associated with substrate inhibition.

Original languageEnglish (US)
Pages (from-to)367-374
Number of pages8
JournalHormone Molecular Biology and Clinical Investigation
Volume3
Issue number1
DOIs
StatePublished - Dec 1 2010

Keywords

  • Dehydroepiandrosterone
  • Dimerization
  • Maltose binding protein
  • Substrate inhibition
  • Sulfation
  • Sulfotransferase
  • SULT2A1

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Medicine(all)
  • Molecular Biology
  • Endocrinology

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