Crystal structure of 3-hydroxybenzoate 6-hydroxylase uncovers lipid-assisted flavoprotein strategy for regioselective aromatic hydroxylation.

S. Montersino, R. Orru, A. Barendregt, A.H. Westphal, E. van Duijn, A. Mattevi, W.J.H. van Berkel

Research output: Contribution to journalArticleAcademicpeer-review

32 Citations (Scopus)

Abstract

3-Hydroxybenzoate 6-hydroxylase (3HB6H) from Rhodococcus jostii RHA1 is a dimeric flavoprotein that catalyzes the NADH- and oxygen-dependent para-hydroxylation of 3-hydroxybenzoate to 2,5-dihydroxybenzoate. In this study, we report the crystal structure of 3HB6H as expressed in Escherichia coli. The overall fold of 3HB6H is similar to that of p-hydroxybenzoate hydroxylase and other flavoprotein aromatic hydroxylases. Unexpectedly, a lipid ligand is bound to each 3HB6H monomer. Mass spectral analysis identified the ligand as a mixture of phosphatidylglycerol and phosphatidylethanolamine. The fatty acid chains occupy hydrophobic channels that deeply penetrate into the interior of the substrate-binding domain of each subunit, whereas the hydrophilic part is exposed on the protein surface, connecting the dimerization domains via a few interactions. Most remarkably, the terminal part of a phospholipid acyl chain is directly involved in the substrate-binding site. Co-crystallized chloride ion and the crystal structure of the H213S variant with bound 3-hydroxybenzoate provide hints about oxygen activation and substrate hydroxylation. Essential roles are played by His-213 in catalysis and Tyr-105 in substrate binding. This phospholipid-assisted strategy to control regioselective aromatic hydroxylation is of relevance for optimization of flavin-dependent biocatalysts.
Original languageEnglish
Pages (from-to)26235-26245
JournalJournal of Biological Chemistry
Volume288
DOIs
Publication statusPublished - 2013

Keywords

  • para-hydroxybenzoate hydroxylase
  • coenzyme-q biosynthesis
  • pseudomonas-fluorescens
  • genus rhodococcus
  • mass-spectrometry
  • escherichia-coli
  • data quality
  • substrate
  • enzyme
  • sequence

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