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Publication Abstract from PubMed

3-Hydroxybenzoate hydroxylase from Rhodococcus jostii RHA1 (3HB6H) is a dimeric flavoprotein that catalyses 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 (PHBH) and other flavoprotein aromatic hydroxylases. Unexpectedly, a lipid ligand is bound to each 3HB6H monomer. Mass spectral analysis identifies 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 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 His213Ser variant with bound 3-hydroxybenzoate provide hints about oxygen activation and substrate hydroxylation. Essential roles are played by His213 in catalysis and Tyr105 in substrate binding. This phospholipid-assisted strategy to control regioselective aromatic hydroxylation is of relevance for optimization of flavin-dependent biocatalysts.

Crystal structure of 3-hydroxybenzoate 6-hydroxylase uncovers lipid-assisted flavoprotein strategy for regioselective aromatic hydroxylation.,Montersino S, Orru R, Barendregt A, Westphal AH, van Duijn E, Mattevi A, van Berkel WJ J Biol Chem. 2013 Jul 17. PMID:23864660^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.